INFLUENCE OF LOW NIGHT TEMPERATURES ON SWEET-PEPPER FLOWER QUALITY AND THE EFFECT OF REPEATED POLLINATIONS, WITH VIABLE POLLEN, ON FRUIT SETTING

The effects of night temperatures on the functioning and fertility of flower parts and, thereby, on fruit set and fruit shape in sweet peppe r (Capsicum annum L.) were studied. In cv. Mazurka style length was po sitively, and the ovary diameter was negatively, correlated with the d ecrease in night temperatures. The functioning of the flower female or gans was also affected by low (14 degrees C or less) night temperature s, and the number of viable pollen grains per flower was markedly redu ced and their germinability was impaired. Fruits which set under low n ight temperatures were deformed (and generally seedless), whereas unde r higher night temperatures most of the fruits were of the normal, blo cky type. The male and female flower organs of cv. 899 were less sensi tive to low temperatures than those of cv. Mazurka, so that all the fr uits of cv. Mazurka which had set under low night temperatures were sm all and seedless (flattened) or pointed, while more fruits of cv. 899 were larger, seeded and of better shape. Nevertheless, a single pollin ation of flowers grown under a night temperature of 12 degrees C with pollen originated from a night temperature of 18 degrees C brought abo ut a markedly greater percentage of normal fruits in both cultivars. D ouble pollination of the same flowers further increased fruit size and improved the shape; three successive pollinations had greater effect. The flowers of cv. 899 showed a greater response than those of cv. Ma zurka to the repeated pollinations, in increased seed production, incr eased fruit size and improved fruit shape. These results indicate that pollen viability is important in determining the size and shape of fr uits developed under low temperatures, and that repeated pollinations, which mimic bees' activities in a greenhouse, can considerably increa se yields and improve fruit shape, thereby improving the farmer's inco me.