The Effect of Calcium on Photosynthetic Rate due to ABA and Proline Behaviour of Oil Palm (Elaeis guineensis Jacq.) Seedlings under Drought Conditions

Planting drought-resistance plants in terms of agronomy, such as induction of plant tolerance using calcium is assumed to be able to solve the climate anomaly problem. Calcium is known as an element that plays an essential role in determining the response of plant resistance to drought through biochemical activity. This study aimed to determine the role of calcium in changing photosynthesis activity in order to increase the resistance to drought stress. The treatment was arranged in factorial of 3 x 4 in a split plot Randomized Complete Block Design replicated three times. The first factor was the dose of calcium application consisted of 0 (control/without calcium), 0.04, 0.08 and 0.12 g. The second factor was the intensity of drought stress, which referred to the Fraction of Transpirable Soil Water method consisted of 1 (control/field capacity), 0.35 (moderate drought) and 0.15 (severe drought). The measurement data of stomatal aperture, Abscisic Acid (ABA) content, chlorophyll content, carotenoid content, proline content, nitrate reductase activity and photosynthesis rate that fulfill the assumption of homogeneity and normality were analyzed using variance at 95% accuracy and continued using DMRT. Moreover, regression analysis were determined of relationship between the treatment and parameters. The results revealed that drought resulted in a decline in leaf water potential and stomatal aperture. The effects of calcium on chlorophyll and carotenoid under drought stress could not be explained in this study. However, the application of calcium has a significant effect on decreased ABA, increased proline and nitrate reductase activity resulting in an increase in the photosynthetic rate of oil palm seeds in drought stress