NCERT Solutions For Class 11 Biology Plant Growth and Development
Topics and Subtopics in NCERT Solutions for Class 11 Biology Chapter 15 Plant Growth and Development:
|Section Name||Topic Name|
|15||Plant Growth and Development|
|15.2||Differentiation, Dedifferentiation and Redifferentiation|
|15.4||Plant Growth Regulators|
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This is a..Therefore, it is a change in form and activity.A process leading to specialisation in a particular function.Development allows for the sequential development of a cell, organ, or organism, e.g., seed germination, growth, differentiation, flowering, seed formation, and senescence.Dedifferentiation is the process by which differentiated cells that have ceased to divide due to certain circumstances become meristematic and regain their divisibility. .A meristem is a tissue that provides a continuous source of new cells throughout the body by means of unspecialised immature cells.The growth rate is defined as the rate of growth per unit time.
2. Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant?Solution: A flowering plant consists of a number of organs viz., roots, stem, leaves, flowers, fruits etc. growing differently under different stages of life cycle. These plant organs require different parameters to demonstrate their growth. In plant organs like fruits, bulbs, corms etc. fresh weight is used for measuring their growth. In case of fruits, increase in volume, diameter etc., are also used as other parameters for the measurement of their growth. For flat organs like leaves, increase in surface area is used as the parameter. Stem and roots primarily grow in length and then in girth, thus increase in length and diameter are used for measuring their growth. Consequently, the flowering plants exhibit several parameters to demonstrate growth.
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In three. .The rate of growth is constant, and growth occurs in arithmetic progression, e.g., the length of a plant is measured every two hours at 2, 4, 6, 8, 10-12 cms.A root or shoot that extends at a constant rate has this protein.In arithmetic growth, Lt = L0 + rt, Lt is the length at time t.For length at the beginning, L0, r equals the growth rate.
Four.List the five main groups of natural plant growth regulators.Provide an overview of each group's discovery, physiological functions, and agricultural/horticultural applications. Solution: Plants have five primary groups of hormones that can be described as hormones of nature.The five groups are:
. .Went (1928) further refined this experiment and corroborated the findings of Paal.He was the first to isolate and name these compounds from tip of the plant as auxins (Greek Auxein means "to grow"). In 1931, Kogl and Haagen-Smith isolated crystalline compounds in human urine. These were named auxin-a, auxin-b, andheteroauxin.
Physiological functions of auxins:
Agricultural/horticultural application of auxins:
Five.Can you explain to me what photoperiodism and vernacularisation mean?. .Plants respond to relative lengths of light and darkness by flowering.
The sixth point..hormone?hormone? The answer is that ABA is a fairly high concentration in leaves of plants growing under stressful conditions, such as drought, flooding, injury, mineral deficit, etc.It is accompanied by the loss of turgor and dilation of stomata.Upon transfer to normal conditions, such plants reestablish normal turgor and ABA concentrations decrease.
Seven.Higher plants have both open growth and differentiation.Solution: Plant growth is indeterminate.There are specific areas in higher plants called meristems that produce new cells. .Differentiation is always correlated with growth.No one knows how differentiation occurs.Furthermore, the growth of plants and their differentiation are both open-ended. .In this sense, both processes are indeterminate, varying in their development, i.e., both are open.
Eighth.A short day plant and a long day plant can both produce flowers simultaneously at the same time.Short day plants (SDP) flower only in dark environments and short photoperiods, such as Xanthium, Dahlia, etc.Long day plants (LDP) may flower only when they receive long photoperiods and short dark periods, such as wheat and oat.The critical photoperiod is that continuous duration of light which cannot be exceeded in the SDP and should always be exceeded in the LDP in order to bring them to bloom.For Xanthium, light must be provided for less than 15.6 hours, while for Henbane, it must be provided for more than 11 hours.Plants that flower at approximately the same time include Xanthium (a SDP) and Henbane (DP).
The tenth point.Could a defoliated plant respond to photoperiodic cycles?.Why?Why? A plant that is defoliated will not respond to the photoperiodic cycle because photoperiodic signals are carried exclusively by leaves.
The eleventh paragraph.