PLANT POLYAMINES IN REPRODUCTIVE ACTIVITY AND RESPONSE TO ABIOTIC STRESS

In this review we will focus on two areas in which the accumulated evi dence for a critical physiological role of polyamines is becoming comp elling, i.e. reproductive activity and response to abiotic stress. Reg arding reproductive behavior, it seems clear that polyamines are membe rs of the array of internal compounds required for flower initiation, normal floral organ morphogenesis, fruit growth and fruit ripening in particular plant species. Abiotic stresses such as osmotic stress can ''turn on'' arginine decarboxylase (ADC) genes, resulting in a rapid i ncrease in their mRNA levels. Localization of ADC enzyme in the chloro plast suggests a role of PAs in the maintenance of photosynthetic acti vity during senescence responses induced by osmotic stress. We envisag e that the use of transgenic plants and improved molecular probes will resolve in the near future the physiological significance of stress-i nduced changes in PA metabolism as well as the role of these compounds in reproductive activity.