Abstract:

In order to explore the changes in the physiology and morphology of wheat roots under low phosphorus stress and its effect on the uptake capacity of cadmium， this paper investigated the morphological and exudate changes of wheat roots under low phosphorus stress with Ca₃（PO₄）₂ as the phosphorus source， and the effects of these changes on the mobilization and uptake of insoluble cadmium （CdCO₃） through sand culture study. The results showed that low phosphorus treatment decreased the biomass of wheat by 27.3% compared to the control （P<0.05）， as well as decreased root length， root surface area and root volume significantly （P<0.05）. In addition， low phosphorus treatment reduced the plant phosphorus contents of aboveground and underground by 35.4% and 23.1% （P<0.05）， respectively， but promoted the dissolution of insoluble phosphorus （P<0.05）. It was also found that low phosphorus stress significantly increased the cadmium content and total mobilization of cadmium in wheat plants by 190.8% and 82.8% （P<0.05）， respectively. The pH of the medium reduced by 0.3 under low phosphorus stress， while the oxalate and malate contents in the roots significantly increased by 1 588.1% and 37.7% （P<0.05）， suggesting that wheat might promote phosphorus mobilization， as well as cadmium， through secreting proton and carboxylate roots under low phosphorus stress， which caused the increase of cadmium uptake in wheat. These results elucidated the mechanism by which low phosphorus stress affected cadmium uptake in wheat.

Key words: wheat, phosphorus, cadmium, root secretion, mobilization

摘要：

为探究低磷胁迫下小麦根系生理和形态的变化及其对镉的吸收能力的影响，以Ca₃（PO₄）₂作为磷源，通过砂培试验研究了在低磷胁迫下小麦根系形态和分泌物变化特征，以及这些变化对难溶态镉（CdCO₃）的活化与吸收的影响。结果表明，在低磷处理中，小麦地下部生物量显著低于对照，降幅为27.3%（P<0.05），根长度、根表面积和根体积均显著变小（P<0.05）。此外，低磷胁迫下小麦地上部和地下部磷含量均显著降低，降幅分别为35.4%和23.1%（P<0.05），但是显著促进了难溶态磷的溶解（P<0.05）。同时还发现低磷胁迫显著提高了小麦植株Cd含量和Cd的总活化量，增幅分别为190.8%和82.8%（P<0.05）。低磷胁迫下培养基pH降低了0.3，同时根中草酸根和苹果酸根含量显著升高，增幅分别为1 588.1%和37.7%（P<0.05），由此可见，低磷胁迫下小麦通过分泌质子和羧酸根促进了磷的活化，并促进了Cd的活化，进而导致小麦Cd吸收的增加。这些结果阐明了低磷胁迫影响小麦Cd吸收的机制。

关键词: 小麦, 磷, 镉, 根系分泌物, 活化