Plant Growth And Development

• Plants have meristems that allow for unlimited growth throughout their life
• Meristems are responsible for primary growth and elongation of plants
• In dicotyledonous plants and gymnosperms, lateral meristems like vascular cambium and cork-cambium cause secondary growth, increasing the girth of organs
• Growth is an irreversible permanent increase in size of an organ, its parts, or individual cells, accompanied by metabolic processes
• Growth can be measured by parameters like increase in fresh weight, dry weight, length, area, volume, and cell number
• Growth is generally divided into three phases: meristematic, elongation, and maturation
• Growth rates can be arithmetic or geometric, with arithmetic growth exemplified by a root elongating at a constant rate
• Geometric growth starts slow, increases rapidly, and then slows down due to limited nutrient supply
• Conditions for growth include water, oxygen, and nutrients as essential elements
• Plant cells require water, oxygen, and nutrients for growth
• Plant cells grow in size by cell enlargement, which requires water
• Turgidity of cells helps in extension growth
• Plant growth and development are closely linked to the water status of the plant
• Water provides the medium for enzymatic activities needed for growth
• Oxygen helps in releasing metabolic energy essential for growth activities
• Nutrients (macro and micro essential elements) are required by plants for the synthesis of protoplasm and act as a source of energy
• 2,4-D is widely used as a herbicide to kill dicotyledonous weeds
• 2,4-D does not affect mature monocotyledonous plants
• Auxin controls xylem differentiation and helps in cell division
• Gibberellins are a type of plant growth regulator (PGR) with more than 100 reported forms
• Gibberellic acid (GA3) is one of the most intensively studied forms of gibberellins
• Gibberellins can increase the length of grape stalks and cause fruits like apples to elongate and improve their shape
• Gibberellins delay senescence and can be used to extend the market period of fruits
• Spraying sugarcane crops with gibberellins can increase stem length and yield by up to 20 tonnes per acre
• Gibberellins promote bolting in plants like beet and cabbages
• Cytokinins have specific effects on cytokinesis and were discovered as kinetin from herring sperm DNA
• Kinetin, a form of cytokinin, does not occur naturally in plants
• Cytokinins help in the delay of leaf senescence and promote nutrient mobilisation
• Ethylene is a gaseous PGR that influences various plant processes like seed germination and fruit ripening
• Ethylene is highly effective in fruit ripening and enhances the respiration rate during the process
• Ethylene is widely used in agriculture to regulate various physiological processes in plants
• Abscisic acid (ABA) acts as a general plant growth inhibitor and an inhibitor of plant metabolism
• ABA stimulates the closure of stomata and increases plant tolerance to stresses
• ABA plays a role in seed development, maturation, and dormancy
• Plant growth and development are controlled by intrinsic factors like plant growth regulators (PGRs) and extrinsic factors like light and temperature