what are plant harmones explain them
Asked by | 22nd Nov, 2009, 05:15: PM
Plant hormones are chemicals that regulate plant growth. Plant hormones are signal molecules produced at specific locations in the plant, and occur in extremely low concentrations. The hormones cause altered processes in target cells locally and at other locations. The different hormones present in plants are auxins, gibberellins, cytokinins, abscisic acid and ethylene.
Auxins are phytohormones, which help to coordinate growth and development in the plant body. Auxin stimulates cell elongation. Together with cytokinins, auxins stimulate cell division. Auxins breaks the root apical dominance induced by cytokinins and induce new root formation. But they induce shoot apical dominanace. Auxins are responsible for causing phototropism, geotropism and hydrotropism.
Gibberellins are plant growth hormones inflencing a range of developmental processes in higher plants.They help in growth and elongation of the stem by stimulating cell division and elongation.They break seed dormancy in some plants. They also stimulate flowering in plants. Gibberellins can cause seedless fruit development and can delay senescence in leaves and fruits. They also stimulate enzyme production in germinating cereal grains. Cytokinins promote cell division and hence they are present in greater concentration in areas of rapid cell growth.
Abscisic acid inhibits growth in plants . It also causes wilting of leaves.
Ethylene is a gaseous hormone important in ripening of fruits
Answered by | 23rd Nov, 2009, 10:23: AM
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