Internal Factors Affecting Plant Growth Plant Growth Regulators

Plant Hormones Stimulate or inhibit growth Produced in growing tissue (meristems) Regulated by environmental conditions

Plant Hormones AUXINS primarily promote cell elongation stimulate apical bud growth, inhibit lateral bud growth Stimulate ripening of fruit present in very low quantities, but exert a strong influence synthetic auxins have many uses, including fruit ripening and herbicides

Plant Hormones GIBBERELLINS promote cell division and elongation in shoots in some plants, they cause stems to elongate just before plant flowers (raises flower toward pollinators and wind) dwarf varieties of some plants have a gene mutation which blocks synthesis of gibberellins Commercially, used to stimulate seed germination

Plant Hormones GIBBERELLINS promote cell division and elongation in shoots dwarf varieties of some plants have a gene mutation which blocks synthesis of gibberellins Fig. 4: Arabidopsis mutant with & without gibberellin.

Plant Hormones CYTOKININS stimulate cell division and leaf mesophyll growth mostly in endosperm tissue and young fruit commercially, used in the expanding field of biotechnology and in new tissue cultures, which allows the production of many new (genetically altered) plants

Plant Hormones CYTOKININS Delays leaf senescence (color change) Effect of cytokinin application on leaf senescence.

Plant Hormones ETHYLENE significant role in fruit ripening many fruits begin to produce ethylene gas just before fruit ripening related to both colour change and softening of tissue of ripening fruit ethylene can be applied externally when they want fruit to ripen

Plant Hormones ETHYLENE significant role in fruit ripening many fruits begin to produce ethylene gas just before fruit ripening

Plant Hormones ABSCISIC ACID important in promoting closure of stomata, provides resistance to water stress