FRUITING AND SHADING EFFECTS ON METABOLIC HEAT RATES OF INFLORESCENCEBUDS, CURRENT-YEAR, AND ONE-YEAR-OLD SHOOTS OF KERMAN PISTACHIO TREES

Isothermal microcalorimetric measurements of metabolic heat rates of ' Kerman' pistachio (Pistacia vera L.) individual inflorescence buds, cu rrent-year and 1-year-old shoots were used to investigate the roles of current and reserve photosynthates in the abscission of inflorescence buds. In the early stages of development metabolic heat rates of indi vidual inflorescence buds were two and three times those of individual current-year and 1-year-old shoots respectively. Individual shoot org ans (1-year-old shoots, current-year shoots, and inflorescence buds) s ampled from ''on'' trees had higher metabolic heat rates than similar individual organs sampled from ''off'' trees. Artificial shading of pi stachio trees for 14 days in early June depressed metabolic heat rates of individual inflorescence buds within 24 h, but there was a delay o f 4 days before the decline in metabolic heat rates of individual curr ent-year and 1-year-old shoots. This suggests that metabolic heat rate s of individual inflorescence buds apparently depended on currently fi xed photosynthates.