Influence of low night temperatures on sweet pepper flower quality and the effect of repeated pollinations, with viable pollen, on fruit setting

Abstract

SummaryThe effects of night temperatures on the functioning and fertility of flower parts and, thereby, on fruit set and fruit shape in sweet pepper (Capsicum annum L.) were studied. In cv. Mazurka style length was positively, and the ovary diameter was negatively, correlated with the decrease in night temperatures. The functioning of the flower female organs was also affected by low (14°C or less) night temperatures, and the number of viable pollen grains per flower was markedly reduced and their germinability was impaired. Fruits which set under low night temperatures were deformed (and generally seedless), whereas under higher night temperatures most of the fruits were of the normal, blocky type. The male and female flower organs of cv. 899 were less sensitive to low temperatures than those of cv. Mazurka, so that all the fruits of cv. Mazurka which had set under low night temperatures were small and seedless (flattened) or pointed, while more fruits of cv. 899 were larger, seeded and of better shape. Nevertheless, a single pollination of flowers grown under a night temperature of 12°C with pollen originated from a night temperature of 18°C brought about a markedly greater percentage of normal fruits in both cultivars. Double 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. Mazurka to the repeated pollinations, in increased seed production, increased fruit size and improved fruit shape. These results indicate that pollen viability is important in determining the size and shape of fruits developed under low temperatures, and that repeated pollinations, which mimic bees’ activities in a greenhouse, can considerably increase yields and improve fruit shape, thereby improving the farmer’s income.