Pepper flower buds exposed to low night temperatures or a high source:sink ratio for as little as one week exhibit ovary swelling and resultant fruit malformation. Darnell et al. examine the interaction of night temperature and source:sink ratio on cell number and size in ovaries of pepper, Capsicum annuum, at anthesis. They find that a combination of low night temperature (12 °C) and high source:sink ratio increases ovary swelling compared with high night temperature (20 °C) and low source:sink ratio. Ovary swelling is due primarily to increased cell size and number in mesocarp tissue of the ovary wall. Modification of the source:sink ratio can thus ameliorate excessive ovary swelling that occurs under low temperature conditions.