The effect of season on the growth and maturation of bell peppers

Bell peppers grown in greenhouses in the Mediterranean region are frequently subjected to high temperatures in summer and low temperatures in winter. The present experiment was designed to quantify the effect of season on pepper fruit growth, maturation and ripening. Three bell pepper (Capsicum annuum L.) cultivars (Yolo Wonder, California Wonder and E84066) were cultivated in an unheated greenhouse during summer and autumn. Fruit size, fresh weight and volume were higher in the autumn due to increased fruit length and pericarp weight. However, colour transition from green to red was significantly delayed in the autumn and the vitamin C concentration was also lower than in the summer. Similarly, the internal C2H4 concentration was lower at the mature red stage of the autumn-grown fruit than in the summer, whereas the respiration rate and the internal CO2 concentration did not differ. Irrespective of season, the internal C2H4 and CO2 concentrations correlated with the number of seeds per fruit, suggesting that seed metabolism significantly influenced the internal atmosphere of the fruit. Additionally, the number of seeds per fruit in the autumn correlated with fresh fruit weight and volume, but not in the summer. In conclusion, bell pepper fruits produced in the autumn were larger in size, but lower in nutritional value (less vitamin C), while the effects of growth season on the pepper fruit morphology and physiology closely related to the number of seeds per fruit in autumn, but to a less extent in summer.