Effects of Soil Moisture Stress on the “Free Proline” and “Chlorophyll a” Contents of Selected Tomato (Solanum esculentum Mill.) Cultivars in the Sandy Regosols

Abstract

Moisture deficit is often the major factor inhibiting crop yields in semi–arid and arid regions. An induction of moisture stress in plants is known to trigger several biochemical changes. Free proline accumulation and changes in the chlorophyll content of leaves are some of the important biochemical responses to moisture stress. A study was conducted to investigate the effect of moisture stress on “free proline” and “chlorophyll a” contents of selected tomato cultivars. Tomato cultivars ‘KC 1’, ‘Roma’ and ‘Thilina’ were used for this study. The experiment was arranged in a 3 × 2 factor factorial Randomized Complete Block Design with six treatments, which replicated four times. Moisture stress was imposed for the ‘KC 1’, ‘Roma’ and ‘Thilina’ cultivars of tomato for a period of six days in treatments one, three and five. Regular watering was practiced for treatments two, four and six of the above cultivars at two days interval to Field Capacity. The “free proline” and “chlorophyll a” contents were determined for the stressed plants on the 6th day from the commencement of the stress. Moisture stress significantly increased the “free proline” content but reduced the “chlorophyll a” content of leaves of all the tomato cultivars. The highest amount of free proline content (6.2 mgcm power -2) was obtained in the ‘KC 1’ tomato cultivar followed by ‘Roma’ (4.3 mgcm power -2) and ‘Thilina’ (3.1 mgcm power -2). Similarly, the highest amount of “chlorophyll a” content (11.7 mgg power -1 fresh weight) was observed in the ‘KC 1’ tomato cultivar followed by ‘Roma’ (7.3 mgg power -1 fresh weight) and ‘Thilina’ (4.6 mgg power -1fresh weight). Based on the “free proline” and “chlorophyll a” contents, it could be concluded that ‘KC 1’ tomato cultivar was able to resist drought comparatively better than ‘Roma’ and ‘Thilina’.