Organisms are capable of hundreds of chemical reactions. None of these reactions are possible without enzymes. Build-up of new tissues, replacement of old tissues, conversion of food to energy, disposal of waste materials, reproduction - all the activities that are characterized as "life." Enzymes are the substances that allow life to exist at earth temperatures. The living cell is the site of tremendous biochemical activity called metabolism. Metabolism is divided into anabolism and catabolism. Photosynthesis is the most obvious anabolic process in plants. It occurs in all green tissues and...

Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (biochemistry of plants), cell biology, and molecular biology. The movement of materials into and out of the cells in plants takes place in solution or gaseous forms through imbibition, diffusion, permeability and osmosis. Fundamental processes such as photosynthesis, respiration, plant nutrition, plant hormone functions, tropisms, nastic movements,...

Herbicides control undesired grasses and weeds while leaving the crop relatively unharmed. They are classified according to their nature and application time and according to their chemical structure into several groups. Herbicide safeners protect crops from herbicide damage without protecting weeds. Microorganisms, which are pathogenic to some weed species with no pathogenity towards crop plants, can control weeds biologically as bioherbicides. Tolerance to herbicides means the survival of normal population of a species following treatment with a herbicide dosage lethal to other species....