Biology XI: 15 Palnt Gro & Dev(5 Physiological Effects of Gibberell

Physiological Effects of Gibberellins and Cytokinins Gibberellins More than 100 gibberellins are found in different organisms such as fungi and higher plants (denoted as GA1, GA2, GA3, etc.). All GAs are acidic. First gibberellin to be discovered is Gibberellic acid (GA3). It is also the most extensively used. Physiological effects of gibberellins Cause an increase in length of axisThis ability of gibberellin is widely used to increase the length of grapes stalks. Cause fruits to elongate and improve its shape Delay senescence Speed up the malting process in brewing Induce bolting (internode elongation prior to flowering) in beet, cabbage, etc. Cytokinins Discovered as kinetin from autoclaved herring sperm DNA Kinetins do not occur naturally. Zeatin − substance with cytokinin-like activity isolated naturally from corn kernels and coconut milk Physiological importance: Promotes cytokinesis Synthesized naturally in regions undergoing rapid cell divisionFor example, root apices, young fruits, etc. Helps to produce new leaves and chloroplast in leaves Promotes lateral and adventitious shoots; hence, overcomes apical dominance Nutrient mobilization, which delays senescence of leaves