PHOTOSYNTHETIC CHARACTERISTICS OF CAROB TREE (CERATONIA SILIQUA L.) AND CHEMICAL COMPOSITION OF ITS FRUIT ON DIURNAL AND SEASONAL BASIS

Abstract

The photosynthetic capacity of carob tree (Ceratonia siliqua L.) and the quality indices of the fruits growing under natural conditions, at Athens and Rethymno in Greece, were measured on diurnal and seasonal basis. The highest photosynthesis is observed during May compared to June and October, which is correlated well with the high developmental rates, the optimal temperatures and water availability. C. siliqua growing at Athens site attained higher photosynthesis parameters than trees growing in Rethymno. The decline of CO2 assimilation rate during the hot and dry season was rather a non-stomatal effect, since it is not accompanied by low stomatal conductance. Photoinhibition damage during June with concomitant reduction in electron transport rate in Photosystem 2 and Photosystem I may occur. Despite the low soil water and the extremely high air temperatures during the June, carob showed an important capacity to control water loss (A/gs). The total sugar content significantly increases with seasonal changes and reaches its highest value in October when pods are fully ripe, while polyphenols and proteins gradually decrease. The climatic conditions prevailing in the Mediterranean basin do not threaten the survival of C. siliqua.