Dipartimento di Produzione Vegetale, Università degli Studi di Milano, Via Celoria 2, Milan, Italy.
Tree Physiol. 2011 Jan;31(1):102-13. doi: 10.1093/treephys/tpq105.
We analysed Pyrus communis cv. Conference and Cydonia oblonga BA29, differently tolerant to lime-induced chlorosis, to identify the key mechanisms involved in their different performance under Fe deficiency induced by the absence of Fe (-Fe) or by the presence of bicarbonate (+FeBic). Under our experimental conditions, a decrease in root elongation was observed in BA29 under bicarbonate supply. Superoxide dismutase (SOD) and peroxidase (POD) activities were analysed and the relative isoforms were detected by native electrophoresis. The data obtained for both genotypes under -Fe and for BA29 +FeBic suggest the occurrence of overproduction of reactive oxygen species (ROS) and, at the same time, of a scarce capacity to detoxify them. The detection of ROS (O(2)(-) and H(2)O(2)) through histochemical localization supports these results and suggests that they could account for the modifications of mechanical properties of the cell wall during stress adaptation. On the other hand, in the cv. Conference +FeBic, an increase in non-specific POD activity was detected, confirming its higher level of protection in particular against H(2)O(2) accumulation. Peroxidases involved in lignification were assayed and histochemical analysis was performed. The results suggest that only in BA29 under bicarbonate supply can the presence of ROS in root apoplast be correlated with lignin deposits in external layers and in endodermis as a consequence of the shift of PODs towards a lignification role. We suggest that in BA29 the decrease in root growth could impair mineral nutrition, generating susceptibility to calcareous soils. In the cv. Conference, the allocation of new biomass to the root system could improve soil exploration and consequently Fe uptake.
我们分析了不同耐石灰性的西洋梨（Pyrus communis cv. Conference）和榅桲（Cydonia oblonga BA29），以确定它们在缺铁（-Fe）或存在碳酸氢盐（+FeBic）时对铁缺乏诱导的不同表现中涉及的关键机制。在我们的实验条件下，BA29 在碳酸氢盐供应下观察到根伸长减少。分析了超氧化物歧化酶（SOD）和过氧化物酶（POD）的活性，并通过天然电泳检测了相对同工酶。在两种基因型的 -Fe 和 BA29 +FeBic 下获得的数据表明活性氧（ROS）的过度产生，同时解毒能力不足。通过组织化学定位检测 ROS（O(2)(-)和 H(2)O(2)) 支持这些结果，并表明它们可能是细胞壁机械性质在应激适应过程中发生变化的原因。另一方面，在 cv. Conference +FeBic 中，检测到非特异性 POD 活性增加，证实其对 H(2)O(2)积累的保护水平更高。测定了参与木质化的过氧化物酶，并进行了组织化学分析。结果表明，只有在 BA29 中，碳酸氢盐供应下质外体中 ROS 的存在才能与外部层和内皮层中的木质素沉积物相关，这是 POD 向木质化作用转变的结果。我们认为，在 BA29 中，根生长的减少可能会损害矿物质营养，使其易受石灰性土壤的影响。在 cv. Conference 中，将新生物质分配到根系中可以改善土壤的探索，从而提高铁的吸收。
