Until recently, breeding efforts in mass produced food crops centered on high yield production while sacrificing flavor, taste and other quality traits. Now, more emphasis is being placed on the enhancement of nutritional and medicinal properties of the food crops. Aside from merely being considered a source of food, crops are today being looked from a health benefit perspective and even from an environmental standpoint. This volume looks at the use of crops for a myriad of purposes, including the prevention and/or mitigation of various diseases, vaccine and antigen production, biofuel production, and the suppression of weeds.

The present multi-volume treatise has been planned to discuss important aspects of the crop-plant physiological aspects, viz., hormones, nutrients, cell membranes, and induced proteins, as related to different types of stresses each in separate volumes. Another type of stress which can be classed under biotic, environmental (sil) or chemical, viz., the stress of allelochemicals which has not been discussed before as a stress factor, will be discussed in a separate volume emphasizing its practical/ ap-plied aspects, rather than mentioning only the allelopathic effects. In this volume on Hormone Relations, different stresses have been arranged in order of their importance and work done.

To cope with the abiotic stress-induced osmotic problems, plants adapt by either increasing uptake of inorganic ions from the external solution, or by de novo synthesis of organic compatible solutes acting as osmolytes. Of the osmoregulants and protectants discussed in this volume, trehalose, fructans, ectoine and citrulline, which are generated in different species, in osmotically ineffective amounts, mitigate the stress effects on cells/plants and improve productivity. There are several pieces of encouraging research discussed in this volume showing significant improvement in stress tolerance and in turn productivity by involving genetic engineering techniques.

Though plant cells are separated by cell walls, cells maintain their identity as they are delimited by semi-permeable membranes that permit them to function as autonomous units. The flow of materials in and out of the cell is regulated by channels, transporters, pumps, and acquaporins in these membranes. The cytoplasm is sandwiched between two membranes: the plasma membrane, which forms the outer boundary of the cytoplasm, and the tonoplast or the vacuolar membrane which forms the inner boundary. Cell membranes serve several different functions: form boundaries and provide compartmentalization, site of chemical reactions catalyzed by membrane proteins, regulate the exchange of ions/compounds across the barrier, site of perception/transmission of signals (hormones), and act in cell-to-cell communication. The membrane functions are affected by different abiotic (biotic stress not discussed), nutritional, edaphic and mechanical stresses, which have been discussed in this volume in light of the recent literature