Conditions for Growth
⇛ Water, oxygen and nutrients as very essential elements for growth.
⇛ Water
⇛ Indole compounds (indole-3-acetic acid, IAA)
⇛ Adenine derivatives (N6 -furfurylamino purine, kinetin)
⇛ Derivatives of carotenoids (abscisic acid, ABA)
⇛ Terpenes (gibberellic acid, GA3 )
⇛ Gases (ethylene, C2H4 ).
⇛ Some plants require a periodic exposure to light to induce flowering.
⇛ Such plants are able to measure the duration of exposure to light.
⇛ Long day plants require the exposure to light for a period exceeding a well defined critical duration.
⇛ Short day plants must be exposed to light for a period less than this critical duration before the flowering is initiated in them.
⇛ The critical duration is different for different plants.
⇛ There are many plants, however, where there is no such correlation between exposure to light duration and induction of flowering response; such plants are called day-neutral plants
⇛ It is now also known that not only the duration of light period but that the duration of dark period is also of equal importance.
⇛ Flowering in certain plants depends not only on a combination of light and dark exposures but also their relative durations. This response of plants to periods of day/night is termed photoperiodism.
⇛ The site of perception of light/dark duration are the leaves.
⇛ There are plants for which flowering is either quantitatively or qualitatively dependent on exposure to low temperature.
⇛ It prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.
⇛ Vernalisation refers specially to the promotion of flowering by a period of low temperature.
⇛ Some important food plants, wheat, barley, rye have two kinds of varieties: winter & spring varieties.
⇛ The ‘spring’ variety are normally planted in the spring and come to flower and produce grain before the end of the growing season.
⇛ Winter varieties, however, if planted in spring would normally fail to flower or produce mature grain within a span of a flowering season. Hence, they are planted in autumn. They germinate, and over winter come out as small seedlings, resume growth in the spring, and are harvested usually around mid-summer.
⇛ Another example of vernalisation is seen in biennial plants.
⇛ Biennials are monocarpic plants that normally flower and die in the second season. Sugarbeet, cabbages, carrots are some of the common biennials.
⇛ Subjecting the growing of a biennial plant to a cold treatment stimulates a subsequent photoperiodic flowering response.
1. What is plant growth and development? |
2. What are the factors that affect plant growth and development? |
3. How does light affect plant growth and development? |
4. What role do hormones play in plant growth and development? |
5. How do nutrients affect plant growth and development? |
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