Soil Water Supply during Dry Weather Constraint of Sweet Orange (Citrus sinensis L. Osb.) Seedlings in Response to Gas Exchanges, Photosynthetic Functions, Leaf Carbohydrate Contents and Biomass Production

摘要

Regarding the influences and consequences of abiotic stress, dry weather is one of the major causes of crop losses worldwide. The aim of this study was to test the adaptation potential of sweet orange {Citrus sinensis L. Osb.) in dry environmental conditions with a high vapor pressure deficit. Two different soil moisture levels were used in a pot trial for sweet orange seedlings in greenhouse conditions. One year old citrus seedlings, which are grown as exotic plants in semi-arid regions, were studied under moist soil conditions and during mild soil water stress. Higher leaf gas exchange and physiological response values were found for the well-watered soil condition. However, no difference in the total chlorophyll content was observed. In addition,photosynthetic functions were very different in response to soil water status. However, no significant differences were found between the soil water levels for thylakoid light harvesting and leaf carbohydrate content. In addition, there were significantdifferences in biomass partitioning between the well-watered seedlings and the mildly stressed seedlings. Consequently, the total dry mass difference in the entire citrus seedlings was approximately 40% for both soil water levels. This study indicates that citrus seedling could adapt to survive and grow in dry weather conditions with a sufficient soil water supply. The drought stress tolerance of citrus varieties and their adaptation and growth in semi-arid regions are discussed.