Histological examination of low temperatures or TIBA-induced swelling of pepper ovaries

The ovaries of pepper (Capsicum annum L.) plants grown under low night temperatures (12 °C) were larger than those of plants grown under high night temperatures (18 °C). TIBA, applied to young flower buds grown under the higher temperature regime markedly stimulated ovary swelling, similarly to the effect of low night temperatures, whereas, NAA had a much smaller effect. STS or AOA did not reverse or attenuate the effect of either low temperatures or of TIBA. Histological examination of various tissues across the ovaries revealed marked increases in transverse and longitudinal diameters of cell of the swelled ovaries, concomitantly with a smaller increase in the number of cells in the receptacle and placenta. It is suggested that the swelling induced by low night temperatures or TIBA results mostly from the enlargement of all the ovary cells, and only to a smaller extent, by an increase in cell number in some of the ovary tissues. Since TIBA, an auxin transport inhibitor, causes auxin accumulation in the treated organ – in this case the developing ovary – and the auxin NAA stimulated ovary growth, one may conclude that auxins are involved in the observed ovary enlargement, whereas ethylene has no role in this phenomenon.