Calcium Forms, Subcelluar Distribution and Ultrastructure of Pulp Cells as Influenced by Calcium Deficiency in Apple (Malus pumila) Fruits

Calcium in Red Fuji and Starkrimson apples during storage were fractionated by sequentextracting. Localization and distribution of calcium and influence of calcium nutritionon cell ultrastructure were observed by transmission electron microscopy combined within situ precipitation of calcium with an improved method of potassium pyroantimonatetechnique. Results indicated that spraying calcium solution on surface of young fruitsincreased contents of calcium in all forms. During storage, contents of soluble calciumand pectic calcium declined and those in calcium phosphate, calcium oxalate and calciumsilicate increased. Calcium contents of Red Fuji in all forms were higher than those ofStarkrimson, indicating that calcium accumulating capability of Red Fuji fruits precededthat of Starkrimson. Under transmission electron microscopy, calcium antimonite precipitates(CaAP) was mainly distributed in cell wall, tonoplast, nuclear membrane and nucleoplasm,much more CaAP deposited in vacuole. Calcium deficiency during storage leads to decreaseof CaAP in locations mentioned above, disappearance of compartmentation, and entrance ofCaAP to cytoplasm. Transformation from soluble calcium and pectic calcium to calciumphosphate, oxalate and damages of biomembranes structuraly and functionally resultedfrom calcium deficiency during storage were the crucial causation of physiologicaldisorder.

苹果缺钙对果实钙组分、亚细胞分布与超微结构的影响

通过苹果幼果期果面喷钙获得试材,采用逐级提取法测定红富士和新红星两个品种贮藏过程中钙形态的变化;采用焦锑酸钾沉淀-透射电子显微镜观察方法,研究果实细胞中钙的亚细胞分布特点及其相应的超微结构变化。结果表明,随贮藏时间增加,红富士和新红星苹果果实水溶性钙和果胶钙含量下降,磷酸钙和草酸钙以及硅酸钙含量相应增加,与对照不喷钙比较,喷钙明显增加贮藏苹果果实各种形态钙的含量;品种间红富士苹果全钙及各种形态钙含量均显著高于新红星。钙均匀分布于细胞壁、细胞膜、液泡膜、核膜和核质,并在液泡内堆积;缺钙时核膜模糊或断裂,且钙颗粒分布不均,细胞分室作用消失,细胞质中出现大量含钙颗粒。贮藏过程中果实水溶性钙和果胶钙则向磷酸钙和草酸钙的无效化转变,以及由此引起的细胞膜系统结构和功能的损伤,是缺钙导致苹果果实生理失调的重要机理之一。

镉胁迫下钙对镉在玉米细胞中分布及对叶绿体结构与酶活性的影响

采用溶液培养试验、亚细胞组分分级分离技术、透射电子显微镜观察及生化分析等方法研究钙对镉胁迫下玉米根、叶组织镉的亚细胞分布、叶绿体超微结构及叶片RuBP 羧化酶和PEP 羧化酶活性的影响。结果表明,与缺钙加镉处理比较,镉毒害下添加钙,玉米根、叶细胞器和细胞质Cd 组分均显著下降,相应Ca 组分则显著增加,而细胞壁Cd 、Ca 含量各处理间均十分接近;镉毒害下添加钙,维管束鞘细胞基质片层及叶肉细胞基粒和基粒片层排列较好,维管束鞘细胞嗜锇粒大为减少,叶片RuBP和PEP羧化酶活性显著增加。说明Ca 对于Cd 胁迫下玉米叶片正常结构与功能的保持具有十分重要的意义。