TOMATO PHOTOSYNTHESIS MONITORING IN INVESTIGATIONS ON TOLERANCE TO LOW TEMPERATURES

Abstract

At the Physiology Laboratory of the Lithuanian Institute of Horticulture investigation is carried out on tolerance to low temperatures of tomato species and hybrids in greenhouses. In trials with the help of an automatic plant investigation system 'Ecoplant-11' the following physiological parameters are observed: photosynthesis intensity, xylem movement, stem diameter, difference in leaf and air temperatures, parameters of microclimate factors. We observed tomato variety Svara and hybrids Sveikutis F 1 and Pirmutis F 1 that were developed at the LIH. The analysis of investigation data showed that under autumn lighting conditions in Lithuania integral lighting affects the intensity of greenhouse tomato photosynthesis most significantly. Other important factors are temperature and CO 2 amount in the environment. The investigated variety and hybrids distinguish themselves for tolerance to low temperatures, especially the variety Svara. CO 2 assimilation is still observed over the compensation point, at 6-8°C. However, intensity of the process increases when temperature rises. In any case the level of lighting intensity and lighting of separate leaves are most important. Observations of leaf temperature stem diameter changes and dynamics of xylem movement under different temperatures revealed that the variety Svara has greater plasticity when adapting to low temperature conditions. Nearly in all cases the plants of the new hybrid Pirmutis F 1 distinguished themselves for greater photosynthesis intensity, especially when integral lighting was increasing along with other environmental factors changing to optimum. It is possible to suppose that the hybrid will meet the requirements of an intensive tomato crop. The phytomonitoring investigation shows that by selection it is possible to develop tomato forms tolerant to low temperature.