花生荚果钙素吸收机制研究

采用45Ca微观放射自显影、电子探针及特异性抑制剂研究花生荚果钙素吸收机制,结果表明,Ca2+是通过主动吸收由外界进入细胞质中,并以共质体途径在组织和细胞间运输,外果皮的周皮层和中果皮的纤维细胞层对Ca2+质外体运输有一定阻碍作用。钙通道抑制剂与ATP酶特异性抑制剂处理,中果皮和内果皮的薄壁细胞内未见45Ca显影,大量45Ca出现在周皮层,仅微量的45Ca到达中果皮细胞间隙和纤维细胞层质外体空间。电子探针的结果也可看出高钙峰出现在周皮层,而对照处理荚果整个组织的共质体和质外体均有45a的显影,且由外果皮向内,组织中的钙呈逆浓度梯度分布。2,4二硝基酸可抑制荚果钙素吸收速率,其抑制率达7092％。荚果钙素吸收动力学的结果表明,当Ca2+浓度为0-0.5mmol/L时,其吸收速率符合Michaelis-Menten酶动力学模型,Km值为0.0135mmol/L,Fmax为13210-4.mol/(cm2h);而当Ca2+浓度为1-5mmol/L范围时,其表现出复杂的吸收特征,此时Km和Fmax均无法得出明确的数值;供钙浓度为0.5-2.0mmol/L时,荚果干重及果仁干重与吸钙量均可达到最大并趋于稳定。

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 132×10^-4μmol 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.