Introduction to Botany 8-3
Categories of Plants
Plants fall into different categories, determined by the plant's life cycle in the environment.
Annual An annual plant (also known as "determinate") completes its life cycle within
one growing season-from germination of a seed through growth, flowering, production of
seeds and death.
Biennial A biennial plant has a natural life cycle of two growing seasons. The seed is sown in the first
year and the plant grows, usually with vegetative growth. The second year, it flowers and dies.
Perennial A perennial plant (also known as "indeterminate") lives for a number of years and flowers each
There are other divisions of plants based on their hardiness.
Tender Sensitive to the cold (can be annual, biennial or perennial)
Hardy Able to withstand frosts ( can be annual, biennial or perennial)
Plants reproduce by sexual or asexual reproduction or both depending on the species. One of the most important factors that aid in plant growth and reproduction is the availability of nitrogen (N2).
Seeds are the focus of sexual reproduction in plants. As a seeded plant grows, it holds an egg within and when the plant matures, the egg is fertilized by pollen from itself or another plant. Fertilization from other plants usually takes place by the transfer of pollen grains which can be carried by the wind, insects, bees, birds or animals. The fertilized egg (zygote) remains in the plant and eventually becomes a seed ready to produce another plant.
Asexual plant reproduction requires only one organism. There is no change in the chromosome number if a new plant is separated from the parent plant. Single cell division in asexual reproduction does not change the chromosome number. The new plants have the same genetic structure as the parents.
Asexual reproduction includes plants that grow from bulbs (such as tulips), feelers (such as crabgrass) and rhizomes (underground stems). Branches grafted to trees (such as certain types of oranges and grapes) can also be classified as asexual reproduction. Single celled plants (such as algae) also reproduce asexually by ordinary cell division.
Plant Growth Stages for Fruiting Plants:
All flowering plants go through the basic growth stages: seedling, vegetative, early fruiting and mature fruiting. As the plant passes from one phase to another, there are not clear demarcations between the phases. In fact, there is usually overlapping from one to the next.
When a seed has germinated and the cotyledons ( first leaves) emerge, the shoot begins to grow and the plant enters the seedling stage. During this time, providing exactly the right environ- mental conditions and nutrient diet is critical to the well-being of your plant. A healthy seed- ling will be deep in color and will quickly develop new leaves. The stem will grow strong to support the weight of the plant.
An unhealthy seedling will be pale in color and, often, the stem will be weak or break off all together.
The growing conditions under which seedlings are grown affects the fruiting and health of the crop for its entire life.
In a hydroponic system, the seedlings are usually fed a weaker nutrient solution than a mature plant.
The vegetative stage begins when your plants are quickly developing their leafy mass and often continues throughout the plant's life. In fruiting plants, it is important to build a strong plant prior to the development of the first flowers.
The nutrient solution that is being fed to the plants is usually increased to a stronger solution
with a higher percentage of nitrogen in the vegetative stage. The vegetative stage is quite demanding of Nitrogen.
The early fruiting stage begins when the first buds appear on a plant. At this point, specifically with tomato plants, the nutrient concentration is again increased to a stronger solution but the percentage of Nitrogen is decreased.
The mature fruiting stage begins when your fruit begins to ripen. Depending upon the variety of plant and whether or not it is determinate or indeterminate, this stage can last from one month to several years. With an indeterminate variety (which is what most commercial hydroponic tomato growers grow) it is important to balance the vegetative growth with the fruiting. Too much vegetative growth will halt fruiting and produce an unruly plant. Too heavy of a fruit load will result in the plant halting new flower production until the fruit load in lessened resulting in uneven harvesting.
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