不同铁营养状况下根系特征及蒸腾对黄瓜幼苗吸收镉的影响

采用营养液培养方法,研究了不同铁营养状况下的根系形态变化及蒸腾作用对不同品种黄瓜幼苗吸收镉的影响.结果表明,不加铁处理对地上部生物量的影响大于对根系的影响,并且不同品种间生物量差异显著.不加铁处理和低水平铁处理时,黄瓜根长变长、根表面积变大.与不加铁处理相比,加铁处理显著抑制了黄瓜根系对镉的吸收,中农5号(缺铁敏感黄瓜品种)和津春4号(缺铁不敏感黄瓜品种)每克根对镉的吸收量分别降低了25.5%~45.5%和28.8%~55.0%;但却增加了镉向地上部的转运,镉在叶中的分配系数分别增加了2.2~3.6倍(中农5号)和2.6~3.7倍(津春4号).缺铁敏感的中农5号吸镉总量与根长、根表面积都呈显著正相关性,而缺铁不敏感的津春4号吸镉总量与根长、根表面积之间的关系不显著.不管是中农5号还是津春4号,其蒸腾速率与每克根吸收镉的量均呈显著的正相关关系.不同铁营养状况影响了黄瓜幼苗的根系形态和蒸腾速率,从而影响了根系对镉的吸收,高铁水平显著抑制了黄瓜根系对镉的吸收.

Effects of root characteristics and transpiration on cadmium uptake by cucumber seedlings under varied iron levels

A hydroponic experiment with two cucumber cultivars was conducted to study the cadmium (Cd) uptake by cucumber seedlings and its correlations with root characteristics (root length and root surface area) and transpiration under varied iron (Fe) levels. There were significant differences in biomass between the two cucumber cultivars and among different Fe levels, and the effect of Fe deficiency stress on the biomass of shoot was greater than that of root. The root length and surface area of cucumber became longer and larger under non-or low Fe levels. Compared with the non-Fe treatment, addition of Fe significantly inhibited the uptake of Cd by cucumber roots, and the uptake rates of Zhongnong No. 5 (Fe sensitive cultivar) and Jinchun No. 4 (Fe insensitive cultivar) were reduced by 25.5%~45.5% and 28.8%~55.0%, respectively. However, addition of Fe promoted the Cd translocation from roots to shoots, and the distribution coefficients of Cd in the leaves increased by 2.2~3.6 times (Zhongnong No. 5) and 2.6~3.7 times (Jinchun No. 4). A significant positive correlation was observed between total Cd amount with root length and root surface area in Fe-sensitive cultivar of Zhongnong No. 5 but not for Fe-insensitive cultivar of Jinchun No. 4. In addition, a significant positive correlation was also found between the Cd uptake rate and the transpiration rate. Generally, the root morphology and transpiration rate of cucumber seedlings were affected by different Fe nutritional status and the uptake of Cd by the roots. The higher Fe levels significantly inhibited the uptake of Cd by cucumber roots.