Simulation of environmental effects on Ca content in pepper fruit

The main physiological disorders of greenhouse pepper fruit are blossom-end -rot (BER) and fruit cracking, which are affected by environmental conditio ns (temperature, relative humidity and radiation) and calcium (Ca) concentr ation in the fruit. In the literature there is qualitative information on t he relations of Ca translocation and distribution in plant organs, to envir onmental factors, but there is very little quantitative information or math ematical analysis of these processes. The objective of this research was to simulate Ca supply to the growing fruit in relation to environmental condi tions in order to predict the final fruit Ca concentration. For this purpos e a biophysical model of fruit growth was used. The major assumption in the current model is that Ca concentration in the fruit is regulated by the ra tios of phloem/xylem water supply to the fruit. The results are compared wi th experimental data of greenhouse pepper grown in different irrigation fre quencies and different environmental conditions, low air humidity with high temperature and high air humidity with low temperature. The data obtained in those experiments was used to study the effects of the plant water statu s and environment conditions on Ca concentration in the fruit. The main con clusions are: As the Xylem water potential decreases Ca accumulation and co ncentration in the fruit is reduced. As the concentration of carbohydrate i n the phloem increases Ca accumulation in the fruit increases but its conce ntration decreases. The relative humidity of the air effects Ca concentrati on in the fruit through its effect on the water potential of the xylem.