Horticulture for Beginners
Having completed this module you will be able to:
Define horticulture and explain its types.
Explain the significance of propagation in horticulture.
Outline seed propagation and vegetative propagation and explain their benefits.
Explain the reproduction cycle in plants and the types of reproduction.
Outline the various parts of a flower.
Define photosynthesis and list the environmental conditions that must be met for photosynthesis to happen.
Recall the effects of pollution on plant health and reproduction.
What is Horticulture?
Horticulture is the art of growing plants in gardens to make food, medicine, or just for decoration and comfort. Horticulturists are the type of farmer who grows flowers, fruits, nuts, vegetables, herbs, and decorative trees and lawns.
Horticulture, as a field of study and a way of life, goes back thousands of years. Horticulture helped people move from living in nomadic groups to living in settled or semi-settled horticultural groups.
Horticulture is broken up into different fields that focus on growing and processing different kinds of plants and food for different reasons. In order to keep the science of horticulture alive, many groups around the world teach, encourage, and support its development. Luca Ghini and Luther Burbank are two well-known gardeners.
Definition and Types of Horticulture
Horticulture is the practice of improving plant growth, yields, quality, and nutritional value, as well as resistance to pests, diseases, and environmental challenges via the propagation and nurturing of plants.
Additionally, included are the disciplines of arboriculture, plant conservation, landscape restoration, soil management, landscape and garden design, building and maintenance, and construction and maintenance of trees.
Horticulture is derived from the Latin terms hortus and culture, which indicate "garden" and "cultivation" respectively. In contrast to agriculture, horticulture does not involve intensive crop farming, large-scale crop production, or animal husbandry.
Horticulture is modelled after agriculture. In addition, horticulture emphasizes the utilization of smaller plots that are planted with a diverse range of mixed crops, whereas agriculture emphasizes the cultivation of a single major primary crop at a time.
Types of Horticulture
Within the realm of horticultural sciene, there are a number of primary resarch subfields to choose from. They are as follows:
Olericulture
The cultivation of many types of veggies. The cultivation of fruits and nuts is known as pomology, which is sometimes known as fruticulture.
Viticulture
The growing of grapes for consumption (largely intended for winemaking).
Floriculture
The cultivation of blooming plants and other kinds of decorative plants. The cultivation and care of grass fields intended for use in recreational activities, aesthetic purposes, and sports fields is referred to as turf management.
Arboriculture
The planting of individual trees, shrubs, vines, and other perennial woody plants and their subsequent cultivation and maintenance, particularly for the sake of landscape and amenity design.
Horticulture in the landscape
The choice of plants to be utilised in landscape architecture, as well as their production and maintenance.
Postharvest physiology refers to the process of managing harvested horticultural crops in order to delay the onset of deterioration during storage or transportation.
Growing Plants
High-quality fruits and vegetables provide a healthy, balanced diet. Flowers and plants add beauty to our environment. If you want to grow plants in your garden, farm, or homestead, you need to understand plant development and health. First, provide perfect conditions for plants to grow well. Maximize garden space to boost productivity. This applies to ornamentals, fruits, and vegetables.
Healthy plants need a physical substrate for germination, branching, and rooting, as well as light, water, nutrients, and oxygen. Good soil works best. Raised beds can help provide the optimum growing environment.
Choose the proper seed. Certified organic farmers must use organic seeds and seedlings. Vegetable farming requires a stand. To guarantee your seeds or seedlings grow, give the right conditions. Plant diseases and pests ruin gardens. Diagnose plant health concerns before the plant dies. Large-scale tree fruit production requires planning and study. Site planning, climate, marketing, and money are important.
A Healthy landscape
A healthy landscape requires careful plant selection. In the right conditions, plants flourish without much attention. Container gardens can grow almost any plant. But some will grow faster. Consider the climate, soil texture, drainage, grass and decorative needs before buying.
Landscape Horticulture
Production, marketing, and upkeep of landscape plants are all included in landscape horticulture. Professional landscape horticulturists are experts in a wide range of techniques and have an in-depth understanding of when and how to trim trees, shrubs, and other plants. When a tree is trimmed properly, it strengthens its structure, keeps its health, improves its appearance, and raises its value.
Planning a garden landscape also includes evaluating the location, the quantity of water and sunshine the plants will receive, and how well they will coexist. Resources from Penn State Extension are available for planting under different circumstances. You may find information on planting in moist soils, choosing plants that can withstand heat and drought, and more.
Employee landscaping training is offered for new and seasonal employees if you intend to launch a green sector firm. Pruning, planting, watering, mulching, and the most recent landscaping improvements are all covered in basic training.
Propagation
The most fundamental and fundamentally important process in horticulture is known as propagation,
which is the controlled continuation of plants. The two goals that it seeks to accomplish are firstly to
achieve an increase in numbers, and secondly, to retain the key qualities that the plant possesses.
It is possible to propagate a plant either sexually by means of the production of seeds or asexually by means of the utilization of specialized vegetative structures of the plant (such as tubers and corms) or by means of such techniques as cutting, layering, grafting, and tissue culture. Propagation can be accomplished in either of these ways.
Seed Propagation
Self-pollinated plants yield seeds. Self-pollinated plants fertilise egg cells with pollen sperm. Cross-pollinated plants spread through seeds (those whose pollen is carried from one plant to another).
Seeds are the cheapest way to propagate and preserve plants. Dry, cold seed generally lasts until the following planting season. Some last years. Disease-free plants grow from seeds. Viruses are hard to eradicate from plants, and most aren't transmitted by seed. Two issues plague seed propagation. Cross-pollinated heterozygous seeds are genetically diverse. A seedling may not have the same traits as its parents. Second, slow-maturing plants. First-year potatoes don't grow large tubers. Plant propagation solves these issues.
Physical or physiological dormancy prevents many vegetatively generated seeds from germinating. Hard seed coats cause dormancy. Weathering destroys seed coats. Sweet pea seeds have a thick husk that may be sacrificed to let gases and water through. Abrasion, hot water, or acid accomplishes this. Germicides promote dormancy. Seed germination inhibitors can be removed. Cold stratification keeps the seed at high humidity and above-freezing temperatures. Apple, pear, and redbud require cold stratification.
Seed Preservation
Seed preservation is a specialist element of horticulture. Seed technology ensures excellent viability, disease-free, pure, true-to-type seed. Growing, harvesting, cleaning, and distribution may be involved. Tree and shrub seed is gathered from natural stands or cultivated from cuttings. Fruit-processing enterprises sometimes produce rootstock seeds for fruit plants. Seed-growing and plant improvement are connected. Many seed companies use plant-breeding operations to improve their genetics. Threshing collects dry seeds. Fermenting macerated (soaked) pulp or screening recovers seed from fleshy fruits. Size, specific gravity, and surface properties are used to sort and clean seeds. Low humidity and cold temperatures are needed to store seed.
Types of Propagation
Grafting
Grafting is the process of joining together different parts of a plant by making new tissue. The part that
gives the combination its root is called the stock, and the part that is added is called the scion. When
there are more than two parts, the part in the middle is called "interstock." When there is only one bud
on the scion, this is called budding. Grafting and budding are the most common ways to spread plants
through their roots.
When the stock cambium or the scion cambium is cut, it forms groups of cells (called callus tissues) that
grow over the wounds. Grafting is based on how the callus tissues come together when they grow
together.
In dicots, like most trees, the cambium is usually arranged in a continuous ring. The cambium is a layer of actively dividing cells between the wood and bast tissues.
In woody plants, new layers of tissue are made every year. Monocot stems, like those of orchids, don't have a continuous cambium layer or get thicker, so it's hard to graft them.
Vegetative Propagation
Asexual or vegetative reproduction is dependent on plant regeneration. Many plants propagate vegetatively naturally; others do so artificially. Plant propagation is beneficial. These include propagating naturally cross-pollinated or heterozygous plants and seedless descendants. A better plant may be replicated without variation. Vegetative propagation may be easier and faster than seed propagation since it eliminates seed dormancy and the juvenile nonflowering period of some seed-propagated plants.
Vegetative propagation may create clones of horticultural plants, rendering them disease-prone. Vegetative propagation uses apomictic seed, runners, bulbs, corms, rhizomes, offshoots, tubers, stems, and roots, layers and cuttings, grafting and budding, and tissue culture.
Layering and Cutting
Methods can be used to get plants to grow back missing parts, usually new roots or shoots. This is called propagation. When the part that has grown back is still attached to the plant, the process is called
layering. When the part that has grown back is separated from the plant, the process is called cuttage, or
cutting.
Layering happens often on its own. Stems of black raspberries that hang down tend to grow roots where
they touch the ground. The croton is a tropical plant that is often spread by wrapping a cut stem with
moist sphagnum wrapped in plastic to make roots. After the stem has grown roots, it is cut off and
planted. Even though layering is easy and works well, it is not usually used on a large scale in nurseries.
One of the most important ways to spread a plant is by cutting it.
There are many parts of a plant that can be used. Root, stem, and leaf cuttings are the three main types. Most cuttings come from the stem.
Different stems can grow back missing parts in different ways, so plants can be easy or hard to root.
Many different things work together to make it possible for cuttings to grow roots.
There are substances in the plant that can be moved, such as plant hormones (like auxin), carbohydrates, substances with nitrogen, vitamins, and substances that haven't been found yet. Light, temperature, humidity, and the amount of oxygen in the air are all important, as are the plant's age, position, and type of stem.
Plant Reproduction
Plant Reproductive System
For sexual reproduction to happen, DNA from both parents is needed. The male and female sex cells in the parent plants are called gametes.
To make offspring, the genetic material from the male and female gametes joins together. This is known as fertilizations. The genes from both parents are in the seeds that come from fertilizations.
Because of this, the offspring don't have the same genes as either of the parents. If the environment changes, this variety of genes can help them stay alive.
The process by which flowering plants make more of themselves is called pollination. The male parts of the flowers are called stamens, and the female parts are called pistils. The pollen is in the part of the stamen called the anther. This pollen needs to go to a part of the pistil called the stigma.
Flowers - Types of Inflorescence
Flowers are the parts of flowering plants that are used for sexual reproduction, and the different ways
they are arranged can be named:
- A spike is a group of flowers on a single flower stalk that doesn't have separate stems.
- Foxglove, hyacinth, lupine, and wallflower are all examples of flowers with racemes. Each flower has its own stalk, and the stalks are all the same length.
- Compound racemes, such as those found on grasses, have a number of simple racemes arranged in a row on the flower stalk.
- A corymb is like a raceme, but the flower stalks are not all the same length. This means that all of the flowers are at the same level, as in the case of Achillea. Something you see a lot of in hedgerows.
- Umbel flowers have stalks that reach the same height and seem to start at the same point on the main stem. Hogweed is an example of a plant with umbel flowers.
- The capitulum, or composite flower, looks like a disc with flower parts radiating out from the centre as if they were squashed from above. For example, the inula, daisy, and chrysanthemum all have capitula.
The number of flower parts and how they are arranged are the most important ways to classify plants and are also the most important way to identify plants.
Flower Structure
The calyx or ring of sepals, which are usually green and can make food this way, protects the flower while it is still in the flower bud. For the flower parts to grow, the plant has to spend a lot of energy, so the plant's vegetative activities slow down.
The corolla, or ring of petals, can be small and insignificant, like in grasses, or it can be big and colourful, like in flowers that are pollinated by insects. Breeding can be used to change the colour and size of petals on cultivated plants. Petalody, which happens when fewer male organs are made, can also change the number of petals.
Tepals, where the outer layers of the flower look the same, making it hard to tell the sepals from the petals. They are often found in single-celled plants like tulips and lilies.
The male organ is called the androecium. It is made up of a stamen that holds an anther that makes and releases pollen grains.
The female organ, the gynaecium, is in the middle of the flower and is made up of an ovary with one or more ovules (egg cells). The style goes from the ovary to the pollen-catching stigma at the top.
The parts of the flower are on the receptacle, which is at the end of the flower stalk (pedicel).
Nectaries can grow at the base of the petals on the receptacle. These have a secretory function and make things like nectar that attract pollinators.
The flower head or inflorescence has structures that look like leaves. These are called bracts, and they can sometimes attract insects, like in Poinsettia.
(lily cross-section) labels tepals, nectary, stigma/style/ovary (gynoecium), anther/stamen (androecium).
(floral diagram) labels bract, corolla/androecium/gynoecium, and nectary glands on the receptacle region.
(LibreTexts) labels peduncle/pedicel, receptacle, and shows bracts at an inflorescence node.
(Asteraceae) labels the involucral bracts of a flower head (inflorescence), illustrating how bracts can attract pollinators.
Note: “Tepals” are typical of many monocots like lilies and tulips (not “single-celled” plants), which is why the lily diagram is ideal for that label.
The Seed
Sexual reproduction makes a seed, which grows into a new generation of plants with traits from both
parents. The plant has to live through many things that would hurt a growing plant-based organism. The overwintering stage is the seed, which protects the plant from extreme temperatures and amounts of water.
The Seed Structure
The embryo is made up of two parts: a radicle, which will become the main root of the seedling, and a plumule, which will become the shoot system. The hypocotyl connects the two parts. Monocotyledons only have one seed leaf (called a "cotyledon"), while dicotyledons have two as part of their embryo.
In some seeds, like beans, the cotyledons can take up a lot of space. This is because they store food for the embryo.
The most important things about the seed are:
- Embryo, the seed must contain a small, immature plant that is protected by a seed coat so that it can live.
- After fertilisation, the outer layers of the ovule become the testa, or seed coat.
- The pollen tube goes into the testa through a hole called a micropyle, which is a weak spot in the testa.
- Hilum, this is where the fruit is joined to the stem.
Fruiting Plants
For the true fruit to grow, either the ovary has to grow into a juicy, juicy structure or the tissues have to get hard and dry. In false fruits, parts like the inflorescence, as in pineapples and mulberries, and the receptacle, as in apples, become part of the structure.
Animals often eat sweet, juicy fruits, which help the seeds spread and may also cause chemical
changes that break dormancy. Some fruits, which are called "dehiscent," let their seeds fly away into the air. They either use explosives, like brooms and poppies, or tiny parachutes made of feathers, like willow herb and groundsel.
Dry fruits can slowly rot away until their seeds fall out. This is called an indehiscent action. you can see a summary of the different ways that fruits have changed over time, many of which are economically important, as well as how seeds are spread.
Fruit Set
In most species, the process of pollination makes fruit set happen. The hormones, especially gibberellins, that are carried in the pollen cause the ovary to make auxin, which makes the cells grow. Because cucumbers naturally have a lot of auxins, they can make fruit without being fertilised first. This is called parthenocarpy, and it is useful when the goal is to make fruit without seeds.
Such behaviour can be imitated in other species, especially when light and temperature problems have made it hard for species like tomatoes and peppers to set fruit. Here, a chemical that acts like auxin is sprayed on the flowers, but the fruit is usually not very good. Gibberellic acid can be sprayed on pears instead of pollination to make them grow fruit.
Hormonal changes cause fruit to ripen. In tomatoes, this involves a change in the amount of sugar in the fruit at a crucial stage called climacteric. Once this happens, the fruit will continue to ripen and breathe even after it has been taken off the plant. When the fruit ripens, it gives off ethylene, which makes it go bad faster in storage. You can get a plant, like a tomato, to ripen early by spraying it with a chemical, like ethephon, which makes the plant make more ethylene.
Reproduction in Simple Multicellular Green Plants
In horticulture, the plants that make seeds are the most important part of the plant kingdom. Other
green plants with more than one cell can reproduce both sexually and asexually.
Generations change when there are two stages of growth that are very different from each other. In ferns (Pteridophyta), a spore-making body grows on the underside of the leaves during the vegetative stage. Spores are released, and if the conditions are right, they germinate and grow into a sexual leafy stage. During this stage, male and female organs form and release cells that fertilise and grow the plant's body. These spores then grow into new plants while being fed by the sexual leafy stage.
Ferns can be grown from spores if the tiny spores have a damp, sterile environment in which they can grow without competition. It is common for plants to spread by dividing or sending out rhizomes. Many plants can reproduce both by sending out new shoots and by sending new roots.
Plant Growth
Growth is a common phrase in plant science and ecology, although its meaning varies by context and analytical size. Meristem growth involves cell synthesis and organ formation. Growth is typically used synonymously with tissue expansion at the organ or plant size and during short periods. Net primary production describes the growth in broader temporal and geographical dimensions.
Photosynthesis
The following environmental conditions must be met for photosynthesis to happen:
- Carbon dioxide
- Light
- Adequate temperature
- Water
All living things need to eat organic matter to build their bodies and get the chemical energy they need to do things. Even though photosynthesis is the most important process, it is important to remember that many other things are happening all over the plant.
Proteins are being made, and many of them are enzymes that speed up chemical reactions in the leaf, stem, root, and later in the flower and fruit.
Almost every cell's walls are made of cellulose, a complex carbohydrate. In meristematic areas, nucleoproteins are added so that cells can divide.
These are just three examples of many that show growth is much more than just photosynthesis and respiration.
Plant Food Web
All carbon-based organic compounds that are more complicated than water and carbon dioxide must be made from water and carbon dioxide. Many organisms can't make their own food, so they have to eat things like plants and animals that have already made their own food.
Since big animals eat small animals, and small animals eat plants, all living things depend directly or indirectly on photosynthesis in plants. This is the basis of a food web or chain.
Carbon Dioxide and Light
Carbon Dioxide CO2
A plant needs easily available carbon to generate organic molecules like sugars. Carbon dioxide in the air may penetrate into the leaf through the stomata at 330ppm (0.03%). In the air, carbon dioxide flows 10,000 times quicker than via roots. When planting is dense or when plants photosynthesize fast, especially in an unventilated greenhouse, carbon dioxide levels decrease.
This reduces photosynthesis, but a producer may add more carbon dioxide to a greenhouse or polythene tunnel to boost the concentration to 1000 ppm (0.1%) in lettuce. If other elements are available, such techniques will boost plant growth. If any is scarce, the procedure will be slowed.
This theory dubbed the law of limiting factors, holds that the element in the least supply will restrict the pace of the process. It would be inefficient to boost carbon dioxide concentration artificially, e.g. by burning propane gas or releasing pure CO2 gas, if other parameters were not increased appropriately.
Light
Photosynthesis needs light. Any chemical process where two substances combine to generate a bigger
complex requires energy. Sunlight or artificial bulbs power photosynthesis. As with carbon dioxide, the
quantity of light energy present affects the pace of photosynthesis. Simply put, the more light a plant absorbs, the more photosynthesis may occur.
For plant development, light is measured in lumens per square metre, not joules/square metre (lux). Recently,' microwatts per square metre was introduced. One lux equals microwatts per square metre in natural sunshine. Illuminance is an important tool for growers, but it's difficult to determine a plant's exact needs due to species, age, temperature, carbondioxide levels, fertiliser availability, and health.
In summer, the light intensity can reach 50 000–90 000 lux and is not restricting, but between November and February, 3000–8000 lux is limiting for plants growing in a heated greenhouse or polythene tunnel. Clean glass or polythene must be maintained to avoid light-blocking condensation. Artificial lights may boost intensity and lengthen the winter day. These include lettuce, bedding plants, and brassica seedlings.
Temperature
For the complex chemical reactions that happen when water and carbon dioxide combine to make carbohydrates, chemicals called enzymes are needed to speed up the process. Without these enzymes, there wouldn't be much chemical activity. From 0°C to 36°C, the activity of enzymes in living things goes up, and it stops at 40°C. The way the temperature of the air affects the rate of photosynthesis is the same way. But here, the best temperature for plants can be anywhere from 25°C to 36°C. Keep in mind that at very low light levels, the rate of photosynthesis doesn't change much when the temperature goes up. This means that putting heat into the growing area during cold weather won't help much if there isn't enough light.
Water and Minerals
Water
Water is needed for the photosynthesis process, but this is only a very small part of how much water a plant takes in as a whole (see transpiration). Getting water through the xylem is important for keeping the leaf flexible and keeping the stomata open so that carbon dioxide can move into the leaf.
When a leaf has only 90% of its ideal amount of water, the stomata will close and stop carbon dioxide from getting in. This could reduce photosynthesis by as much as 50%. A plant that is clearly dying won't do any photosynthesis at all.
Minerals
The leaf needs minerals to make the pigment chlorophyll, which absorbs most of the light energy needed for photosynthesis. Chlorophyll must be made all the time because it loses its effectiveness quickly.
A plant that doesn't have enough iron or magnesium, especially, turns yellow (chlorotic) and loses a lot of its ability to make food from light (photosynthesis). Diversification also slows the rate of growth.
The Leaf
The leaf is the plant's main organ for photosynthesis, and its cells are set up in a way that makes them work as well as possible. The upper layer of the leaf's epidermis is clear enough to let light pass through to the lower layers of the leaf.
Under the upper epidermis, the sausage-shaped palisade mesophyll cells are packed together and point down. Photosynthesis happens in their chloroplasts, which are small parts of their cells. At one place in the chloroplast, chlorophyll absorbs light, and the energy is sent to a second place where it is used to build up carbohydrates, usually in the form of insoluble starch.
Below the palisade mesophyll is the spongy mesophyll, which is loose and has many air spaces. Gases can move both in and out of these spaces. Carbon dioxide from the air can get to the palisade mesophyll, and oxygen leaves the leaf as a waste product of photosynthesis. The many stomata on the underside of the leaf are the openings to the outside that allow gas to move.
The xylem vessels, which carry water to the photosynthesis reaction, are found in the leaf's many small vascular bundles, or veins. The vascular bundles also have phloem cells, which help move sugar to other parts of the plant. When a leaf first opens, it can take in the most light, but as it gets older, it loses this ability.
Pollution and Respiration
Pollution
Gases in the air, which are usually made by factories or by burning fuel, can hurt plants and often make the leaves look like they are on fire. Fluoride can build up in compost and be found in tap water, which can damage the edges and tips of the leaves of plants like Dracaena and Gladiolus. Heat exchangers that don't work right in glasshouse burners, especially those that use paraffin, can cause sulphur dioxide and carbon dioxide to be made. Before the leaf gets scuffed all over, it turns a reddish colour.
Respiration
So that the plant can grow, it must break down its food in a controlled way to get the energy it needs to make things like cellulose, which is the main part of plant cell walls, and proteins, which are used to make enzymes. This energy is also used to power the division of cells and the many chemical reactions
that happen inside cells.
Different parts of the plant need different amounts of energy, and the reproductive parts can breathe twice as fast as the leaves. Also, apical meristems need a lot of energy for cell division and differentiation processes. In the process of aerobic respiration, oxygen is needed to finish the breakdown.
Storage of Plants
Growing plants get photosynthesis and respiration factors. Removed roots, leaves, or flower stalks stop photosynthesizing, but breathing continues. Carbohydrates, proteins, and lipids are broken down to produce energy, but plant stores are exhausted and dry weight decreases. Reduce respiration rate for stored plant material, whether for a few days, like tomatoes and cut flowers, or several months, like apples.
The following elements can help attain this goal
Temperature
From 36°C (optimum) to 0°C, respiration enzymes become less active. A cold store with temperatures
between 0°C and 10°C is used to keep cut flowers, such as roses, fruit, such as apples, vegetables, such
as onions, and cuttings, such as chrysanthemums, which root more easily afterwards. Gene banks store
seeds in liquid nitrogen at 20°C.
Oxygen and Carbon Dioxide
If there isn't enough oxygen, respiration slows. As with many processes, a buildup of a product slows the process. A controlled environment stored for long-term storage, such as top fruit, is kept at 0° C–5° C and supplied with inert nitrogen gas to exclude oxygen. Some apple varieties raise CO2 by 10%.
Water Loss
Loss of water can damage stored material, such as cuttings. Seeds must not lose so much water they become non-viable, yet too much humidity might cause early germination and loss of viability.
Plant Propagation
Plant propagation is the process of making new plants from seeds, cuttings, and other parts of existing plants. Plant propagation can also mean how seeds are spread by people or by nature.
Most of the time, plant growth has steps that include propagation. For seeds, it happens after they have ripened and been spread out. For vegetative parts, it happens after they have been cut off or pruned. For plants that reproduce without sexual reproduction, like strawberries, it happens as the new plant grows from parts of the old plant.
There are four basic ways to make a plant grow more of itself:
- sexual
- asexual (vegetative)
- layering
- grafting
In horticulture and agriculture, new plants are made every day. Most of the time, seeds and cuttings are used to make more plants.
Seed Propagation
Most plants have sexual reproduction, which makes seeds. Because of how this process works, the seeds that come out of it have different traits to a greater or lesser degree. Most plants grown from seeds won't grow the same way and will be different sizes, have different-coloured flowers, etc.
Skilled plant breeders can control this variation to the point that a high degree of uniformity can be achieved in bedding, for example in terms of flower colour, and vegetable seeds, for example in terms of size and "once over-harvesting".
Sexual reproduction is when a nucleus from the male (in the pollen) and a nucleus from the female (in the ovule) join together to make a new person.
Seeds sprout when they have the right amount of water, air (oxygen), temperature, and, for some, exposure to light or the absence of light. Even when all other conditions are right for germination to happen, it doesn't always happen.
For example, seeds that fall into warm, moist soil in the fall don't sprout until the spring or later. These seeds are in a dormant state, which needs to be broken for germination to happen. This is a survival mechanism that keeps the seed from sprouting just as the weather is about to turn bad for growth.
Sowing and Aftercare in Protected Environments
The best conditions for growing plants from seeds can be found in a protected area, like a glasshouse, or in cheaper options, like polythene tunnels or cold frames. Most seeds that are grown in a controlled environment are planted in containers:
- Trays for seeds
- Halves trays
- Pots (as deep as wide)
- Pans, or "half pots,"
For production horticulture, there are more materials, like polystyrene, that can be used only once. Cost and how the plants look to become the most important factors. Too big of a container wastes compost and space, while too small means the seedlings have to be moved before they're ready. If they're not moved, they get too close together and are more likely to get diseases that kill them.
Sowing Outside
Seed type, soil texture, and climate affect seedbed preparation. Drainage is important. It's excavated or ploughed depending on size. Bury organic trash and weeds. This is best done in the fall if the soil is thick, so frost and rain may break it down. Mellow, worn soil is raked or harrowed in the spring to create the correct tilth for seed germination. Broad beans can be seeded onto a rough seedbed early in the spring, but smaller seeds sown in warmer temperatures should be finer.
Using a false seedbed, hoeing, or weedkillers helps manage weeds. levelled and the phosphate-fertilized ground is seeded. Seeds are either planted in rows or dispersed. Station-sown seeds exist. Large-scale seeding requires equipment. When soil temperatures are right, seeds should be placed at the correct depth and covered to their diameter. The sowing rate varies on species, field conditions, germination, and seed viability.
Vegetative Propagation
All plants can reproduce without a male or female. This is called vegetative propagation in plants. Pieces of the parent plant are cut off and grow into new plants that can live on their own. All living cells have a nucleus that contains a full set of genetic information and can turn into any type of specialized cell (totipotency). At any given time and for any position in the plant, only a small part of all the information is used.
When parts of a plant are taken away, the cells lose their sense of where they belong in the whole plant. This means that they can make organs in places that don't fit with how the plant is usually set up. These are called adventitious and can be rooted on a stem cutting, buds on a piece of root, or roots and buds on a piece of leaf used for vegetative propagation.
Characteristics of Propagation from Vegetative Parts
In horticulture, vegetative propagation is used to make a lot of plants from a single-parent plant. This
group of plants called a clone, is a copy of the parent plant, so they will all have the same genes. The
best thing for horticulturists is to be able to make copies of a cultivar so that all of the new plants have
the same traits.
Some cultivars can only be made again by growing new plants from their seeds. The way that Alchemilla, Rosaceae, Poaceae, and Taraxacum make seeds without fertilisation (called "apomixis") is a special case of natural clonal propagation.
Changes can happen in vegetatively propagated cultivars (see mutations), and some species, called
"sports," have different clonal characteristics within the same cultivar, like the colour of the leaves and
the way the plant grows.
Natural Vegetative Propagation
In the normal course of their growth, many plant species use their ability to spread by sending out new
shoots. The production of these vegetative propagules, as with the production of seed, is to increase
numbers and provide a means by which the plant survives adverse conditions. For this reason, foods like potatoes, onions, and carrots are good for us to eat because they store energy.
All plant growth is a type of division that has been used by people for a very long time. Most of the time, all that is needed is to break up the plant or take the natural seeds.
Divisions and Bulbs
Divisions
Most gardeners know how to split perennials that grow from seeds. Most of the time, this happens when the shoots get too close together, and the thick clumps that form often have woody or bare centres. Borders are refreshed by carefully lifting the clump (called the "crown"), preferably with a ball of soil, removing most of the soil carefully from the roots, and splitting it with back-to-back forks for good leverage.
Smaller ones can be pulled apart by hand, but some are so tough that knives or spades are needed. This can be done in the fall when the plants are dying, but it is usually best to do it in the spring when the new shoots are coming up. Younger parts with strong shoots can be replanted in the ground that has been prepared. This should be done before the roots dry out, and then the plants should be watered.
Bulbs
When bulbs are split in the right way, they can give rise to more than one plant. Scaling is a way to spread scaly bulbs like lilies and fritillaries. The outer scales are removed and put in a polythene bag with a moist material like vermiculite or pushed to half their depth in open propagating compost and covered with polythene. For tunicate bulbs, like tulips, the daughter bulbs inside the parent bulb can be taken out in late summer and grown on in open compost in a warm place.
Methods of Reproduction
Most of the plant's parts can be grown using artificial methods of vegetative propagation. Cuttings are pieces of plants that have been carefully cut away from the parent plants and then used to grow a new plant. This is a way to make more of a lot of different species. For different species, you may need to use different methods. Only parent plants that are healthy should be used. It is very important to use knives, compost, and containers in a clean way. Usually, cuttings are taken from parts of the plant that are still young. The most common ways to take cuttings are briefly explained below.
Cuttings
Stems that are at different stages of maturity can be used to make stem cuttings. Hardwood cuttings
come from pieces of woody stems that are dormant and have buds on them. When dormancy is broken
in the spring, the buds open up and grow into new shoots. The cutting's base is cut cleanly to show the
cambium tissue, from which the new roots will grow. Hydrangea and currant stems have signs of roots
that have already started to grow. These are called "root initials," and they help the roots take hold.
Hardwood cuttings are usually taken in late fall, and they are often put in a growing medium that is half
compost and half sand, with half of their length submerged. Most of the time, it takes a year before the
cuttings can be removed.
Tissue Culture
Tissue culture is a way to make more plants. It works because any part of a plant, from a single cell to the whole apical meristem, can grow into a new plant. The piece of the plant that is taken, called an explant, is grown in a sterile artificial medium that gives it all the vitamins, minerals, and organic nutrients it needs.
The medium and explant are put in a sterile jar or tube and put in an environment that is carefully controlled. This method is better than other ways of spreading plants because it can make a lot of propagules from one original plant. It helps a lot with plants that are rare or new. Another benefit is that it takes less time to grow plant stocks. Some species, like orchids and asparagus, that used to only grow from seeds can now be grown this way.
Summary of Horticulture Basics
The key points from this lesson are:
- Horticulture is the art of growing plants in gardens to make food, medicine, or just for decoration and comfort.
- Horticulture emphasizes the utilization of smaller plots that are planted with a diverse range of mixed crops, whereas agriculture emphasizes the cultivation of a single major primary crop at a time.
- Propagation refers to the process and techniques used for the ‘controlled continuation of plants.’
- Grafting is the process of joining together different parts of a plant by making new tissue.
- The male and female sex cells in the parent plants are called gametes.
- The process by which flowering plants make more of themselves is called pollination.
- Meristem growth involves cell synthesis and organ formation.
- Illuminance is an important tool for growers, but it's difficult to determine a plant's exact needs due to species, age, temperature, carbon dioxide levels, fertilizer availability, and health.
The following environmental conditions must be met for photosynthesis to happen:
- Adequate temperature
- Water
- Carbon dioxide
- Light
Plant propagation is the process of making new plants from seeds, cuttings, and other parts of existing plants.
Vegetative Propagation are pieces of the parent plant are cut off and grow into new plants that can live on their own.
Plant Development and Care
This module covers the following topics:
- Outline the growth and development stages of a plant.
- Describe the optimal conditions needed for the germination of a seed.
- Explain the practical parts of controlling pests, diseases, and weeds in plants.
- List various microorganisms that cause crop plant diseases.
- Outline the role of soil water in plant growth.
- Explain the significance of good soil drainage for plant development.
Introduction To Plant Development and Care
The balance between cell division, expansion, and differentiation determines optimal plant development. Plant development begins with embryogenesis and the construction of the main plant body (embryonic root and embryonic shoot) and continues with the regular generation of new organs postgermination (roots, leaves, branches, and flowers). New cells are created throughout a plant's life in meristems, which include self-renewing stem cells (SCs) that can commit to a spectrum of developmental destinies. During plant development, cells differentiate for a specific function.
Under the right conditions, differentiated plant cells may dedifferentiate and regenerate into entire plants, a process termed totipotency. High plant plasticity permits them to adapt to an ever-changing
environment.