The effects of temperature on flowering, fruit set and fruit development of glasshouse sweet pepper (Capsicum annuumL.)

SummaryThe effects of temperature on flowering, fruit set and fruit development of October sown sweet pepper (Capsicum annuum L.), cv. Delphin, were investigated in a glasshouse experiment. Twelve day/night temperature regimes (16/15, 16/21, 20/12, 20/15, 20/18, 20/21, 24/12, 24/15, 24/18, 24/21, 28/15 and 28/21°C) were applied during the early post- planting period (early December to mid April). Patterns of flowering and fruit set were comparable at similar 24-h mean tempratures. Total number of flowers per plant and percentage fruit set were significantly related to 24-h mean temperature as well as to the day/night temperature amplitude. Mean fruit weight (g per fruit) was related to 24-h mean temperature as well as to the day/night amplitude. For these variables the effect of the day/night amplitude was of minor importance compared with the 24-h mean temperature. No effect of the day/night amplitude was found on the number of fruits (fruits per plant), leaf area/fruit ratio (cm2 fruit−1), fruit length (cm), pericarp thickness (mm), length/width ratio, length of the attached style (cm) and the total growth period of fruits (days). The temperature coefficient (Q10) for the total fruit growth period from flowering to red harvest was between 1.5 and 1.9. It is concluded that the temperature regime (day/ night amplitude) is of minor importance compared with the effect of the 24-h mean temperature for fruit set, fruit development and the growth period of sweet pepper.