STUDY ON MECHANISM OF CALCIUM ABSORPTIONOF PEANUT PODS

The results from the experiment where special inhibitors were used to study the calcium absorption of peanut pods by 45Ca micro-autoradiography and electron X-ray microanalysis showed that calcium was actively absorbped by plasmalemma and entered cytoplasm through ptasmodesmate. Periderm in exocarp and fibroblast layer in mesocarp were the barriers of calcium diffusion in entire tissue, which was concluded from the following two facts: First, in the treatments of Nitrendipine and Sodium Vanadate, 45Ca was absent in cytoplasm of exocarp,mesocarp and endocarp, and deposited mainly in periderm of exocarp where the highest peak of calcium was observed through electron X-ray microanalysis, only a little of 45Ca was distributed in external space of cytoplasm of fibroblast layer in mesocarp. While in the control (CK), 45Ca was found everywhere in tissue and cytoplasm of pods, and the height of peak of Ca decreased from exocarp to testa. Secondly, Ca absorption could be inhibited by 2,4-DNP with an inhibition rate of about 70-90%. The results from study on dynamics of calcium absorption indicated that when Ca concentration ranged from 0-0.5mmolL-1, the relationship between Ca2+ absorption rate and Ca concentration in solution could be described by Michaelis-Menten dynamics Model, where Km was 0. 0135mmolL-1 and Fmax was 13210-4mol cm-2, h-1 but the feature of Ca absorption was too complex to simulate by above Model. From the study on the effect of Ca concentration on dry weight and Ca uptake of peanut pods, the results indicated that dry weight of pods and seeds, and Ca uptake of seeds reached the highest when Ca concentration ranged from 0.5 to 2.0 mmolL-1 and maintained stable even with higher Ca concentration.