A B S T R A C TThe objectives of the study were to determine (1) The level of physiological resistance of oil palm seedlings to drought stress by boron (B) and silicon (Si) application and (2) The mechanism of B and Si actions to induce physiological resistance of oil palm seedlings to drought stress. The B and Si were the elements capably inducing the internal resistance of plant tissues to drought stress, especially through physiological resistance mechanisms. Field trial was arranged in the factorial Randomized Complete Block Design (RCBD) using three blocks as replications. The first factor was six dose of B: 0.00, 0.17, 0.44, 0.87 and 1.31 g plantG 1 . The second factor was five dose of Si: 0.00, 1.15, 2.31, 3.46 and 4.69 g plantG 1 . Observations were done on the Nitrate Reductase Activity (NRA), the content of chlorophyll a, b and total, density, length and width of stomatal aperture, stomatal conductance and transpiration rate, photosynthetic rate and photosynthetic activity per plant, dry weight of plant parts and trunk height and diameter of the oil palm seedlings. The data were analyzed using ANOVA and the means were separated using Duncan's multiple range test at 5% level. Meanwhile, the optimum dose of B and Si were determined using regression analysis. The results showed that B and Si application could induce physiological resistance of oil palm seedlings to drought stress. Mechanism of action of B in inducing physiological resistance of oil palm seedlings to drought stress were by increasing of greenish leaves, width of stomatal aperture and photosynthetic activity per plant while Si application capable to increase of greenish leaves and to decrease the density of lower leaf surface stomatal. The optimal dose of B was 0.33-0.57 g/seedlings and the optimal dose of Si was 2.22 g/seedling in inducing physiological resistance of oil palm seedlings to drought stress.
The difference in the levels of light intensity was responded with changes in morphophysiological and biochemical characters of plants, especially in leaves of black pepper. The aim of this study was to determine the effect of several levels of light intensity on the morphophysiological and biochemical characters of leaves of black pepper. The research was conducted in July - November 2017 in Kemuja, Mendobarat, Bangka Belitung. This study used split-plot design with three replications. The main plots were the levels of light intensity, namely 100%, 75%, and 50%. Subplots were varieties of black pepper, namely Petaling 1, Petaling 2, and Nyelungkup. The results showed that there was no interaction between varieties and light intensities. The morphophysiological and biochemical responses of the leaves of the three varieties tested were the same at all levels of light intensity. Light intensity up to 50% has no effect on leaf morphological characters, but leaves become thinner at lower light intensities. Chlorophyll, nitrate reductase activity and leaf sucrose concentration were same at all light intensities up to 50%. Plants exposed to higher light intensity have a higher number of stomata. The results concluded that the light intensity of up to 50% did not cause changes in leaf morphology and biochemistry and only affected leaf stomata density.
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