水淹对秋华柳根茎细胞壁组分镉含量的影响

为了解水淹胁迫对细胞壁镉富集能力的影响,以秋华柳(Salix variegata Franch)扦插苗为研究对象,设置镉胁迫和水淹胁迫试验,测定了不同处理组下秋华柳根、茎细胞壁不同组分的镉积累特征。结果表明:所有处理组秋华柳存活良好,表现出水淹和镉的双重耐受性;所有镉浓度处理下,秋华柳根、茎细胞壁果胶和半纤维素均具有良好的镉离子结合能力,其中果胶的镉离子结合能力最大;水淹、镉胁迫及两者的交互效应均对秋华柳根、茎细胞壁组分镉含量造成了不同程度的影响。水淹显著降低了茎细胞壁组分镉含量,但对根组分中镉含量无显著影响;水淹条件下,秋华柳根、茎细胞壁果胶和半纤维素镉含量有所降低,但果胶和半纤维素仍为细胞壁镉积累富集的主要组分。上述结果表明,水淹对秋华柳根、茎细胞壁组分中镉的分配策略没有明显改变,镉仍被固定于细胞壁中以减少重金属对植物细胞的伤害,因此秋华柳可以作为三峡库区消落带镉污染土壤修复的备选物种。

Effect of flooding on cadmium content in different cell wall components of the root and stem of Salix variegata Franch

The altered water regime in the Three Gorges Reservoir in the Yangtze River, China, has induced the formation of a hydro-fluctuation zone that has caused many serious environmental problems. Among them, the two main problems are high cadmium concentration in the sediment and anti-seasonal, long-term flooding. Revegetation has become one of the most important means of ecological restoration in the hydro-fluctuation zone of the Three Gorges Reservoir. Previous research has shown that Salix variegata, a native species in the Three Gorges Reservoir, can tolerate both flooding and cadmium stress, and thus is a promising candidate species for revegetation in the hydro-fluctuation zone of the Three Gorges Reservoir. However, the ability of S. variegata to tolerate and accumulate cadmium under flooding is still unclear. In order to investigate the effect of flooding on cadmium content in different cell wall components of the root and stem of S. variegata, cutting seedlings under two water regimes as control group (CK) and flooding group (FL) and four cadmium concentrations (0, 0.5, 2, and 10 mg·kg^-1, achieved by adding CdCl₂·2.5H₂O to the soil) were studied via pot experiments. Sampling was carried out after 60 d of treatment, and the cadmium accumulation characteristics of different cell wall components of the root and stem of S. variegata under different cultivation were analyzed. The results showed as the following:The survival rate of S. variegata for all treatments was high, which indicated high tolerance of this species to flooding and cadmium stresses; In all cadmium treatments, the pectin and hemicellulose of cell wall in the root and stem of S. variegata had good binding capacities to cadmium, and pectin had the highest binding capacity for cadmium; Water regime, cadmium concentration, and the interactions between these two factors had different impacts on the cadmium contents in different cell wall components of the root and stem of S. variegata. Flooding significantly reduced the cadmium content in stem cell wall components, but there was no significant effect by flooding on cadmium content in the root cell wall; The contents of pectin and hemicellulose cadmium in the root and stem cell wall of S. variegata decreased under flooding conditions, but pectin and hemicellulose were still the main cell wall components enriched with cadmium. These results indicated that there was no significant change in the distribution of cadmium in the components of the root and stem cell wall of S. variegata under flooding, as cadmium could still be fixed in the cell wall, to alleviate the harmful effects of cadmium stress on plants. Hence, S. variegata should be considered for phytoremediation of cadmium in the hydro-fluctuation zone of the Three Gorges Reservoir.