Bachelor’s Degree Programme (BSCG) – Plant Physiology and Metabolism Assig Answer | BBYCT–137(Q-10)
10. a) What are the different biochemical and morphological changes recorded in plants in response to stress conditions? Discuss.
b) How does ABA acts as a stress hormone?
a) Plant growth and productivity are adversely affected by environmental stresses. Heavy metal contamination owing to rapid industrialization and agricultural practices, drought, cold stress, high temperature and UV-B radiation are generating agricultural crises in many areas worldwide and causing environmental imbalance. Plants exposed to environmental stresses endure morphological, physiological, and biochemical alteration as well as anatomical changes. These changes help the plants to cope with stress conditions and protect their systems against disturbance. Plants have evolved a range of anatomical changes at organ and organization level. Variations in root, xylem, and leaf anatomy, etc., have been observed in response to environmental stresses. Morphological changes in response to various stresses may appear in the form of reduced growth of internodes, leaf size, leaf surface area, branching pattern, shoot and root growth, etc. Alteration at the anatomical level is mainly due to decreased cell elongation, restricted stimulation of cell division and changes in differentiation conditions of cells, which result in varied anatomical characteristics of plant organs like roots, vascular tissues and leaves. Stresses cause the production of reactive oxygen species, which cause oxidative stress, thereby inducing growth retardation, disturbed photosynthetic apparatus and alteration in the ultrastructure of plant tissues, permeability of plasma membrane, stomatal behavior, etc. In this chapter, we highlight the impact of environmental conditions on the morphology and anatomy of plants.
b)Abscisic acid(ABA) is called stress hormone as it induces various responses in plants against stress conditions. It increases the tolerance of plants toward various stresses. It induces the closure of the stomata during water stress. It promotes seed dormancy and ensures seed germination during favorable conditions. It helps seeds withstand desiccation. It also helps in inducing dormancy in plants at the end of the growing season and promotes the abscission of leaves, fruits, and flowers.