土壤质地对铬胁迫下小麦灌浆期形态与旗叶光合特性的影响

为了探讨铬(Cr)胁迫条件下土壤质地对小麦植株形态及旗叶光合特性的影响,采用盆栽试验方法,研究了3种土壤质地(壤土、粘土、砂土)下灌浆期小麦的根长、分生根数、干物质量等形态指标及旗叶的净光合速率(Pn)、气孔导度(Gs)、胞间CO2浓度(Ci)、蒸腾速率(Tr)、水分利用率(WUE)、叶绿素相对含量等光合特性指标的差异。结果表明,随着Cr胁迫浓度的升高,小麦根长在粘土中呈逐渐变短的趋势,在壤土和砂土上则呈先升高后降低趋势,且根长达到最大值的Cr浓度为100 mg·kg-1;小麦分生根数在3种质地土壤上均呈逐渐减少趋势;Cr胁迫使不同器官的干物质量及干物质总重都有不同程度下降;旗叶的Pn在壤土上也随Cr浓度的升高逐渐降低,在粘土和砂土上则先升高后降低,且当Cr浓度分别为100和200 mg·kg-1时达到最大值;小麦旗叶Gs、Ci、Tr和叶绿素相对含量均呈先升高后降低趋势,且在壤土和粘土上达到最大值的Cr浓度均为100 mg·kg-1,在砂土上为200 mg·kg-1;旗叶WUE在粘土上呈先升高后降低趋势,砂土上则呈现升高趋势,壤土上波动不大。整体来说,Cr胁迫对小麦灌浆期各项光合指标起到了低促高抑或抑制作用,尤其当Cr浓度≥200 mg·kg-1时,Cr对小麦表现出明显的胁迫效应,导致根长降低,分生根数减少,旗叶Gs、Ci、Tr和叶绿素相对含量降低,各器官干物质量减少。此外,在3种质地土壤上,小麦灌浆期旗叶光合指标在Cr胁迫下不同程度下降,砂土的下降趋势比壤土和粘土明显。

Effects of Soil Textures on Morphology and Photosynthetic Characteristics of Flag Leaves of Wheat during Filling Stage in Chromium Polluted Soils

Soil texture is an important factor to effect the toxicity of heavy metal on crop plants. In order to investigate the effects of three textures of soil including loam soil, clay soil and sandy soil on the photosynthetic characteristics of wheat flag leaves under chromium stress, traits of morphology and photosynthesis of wheat, such as plant biomass, length and numbers of root, photosynthetic rate(Pn), stomata conductance(Gs), intercellular CO₂ concentration(Ci), transpiration rate(Tr), water utilization efficiency(WUE), and relative content of chlorophyll were studied during grain-filling stage. The results showed that, with the increasing of chromium concentration, the length of root decreased in clay soil, while it was shown as the trend of increasing first and then decreasing in loam soil and sandy soil, which reaching the peak at the chromium concentration of 100 mg·kg^-1. In three soil textures,lateral root numbers were all reduced as the chromium concentrations increasing; biomass of different organs were decreased also; the Pn decreased in loam soil and showed the trend of increasing first and then decreasing in clay soil and sandy soil, which reached the peak as chromium concentrations was 100 and 200 mg·kg^-1, respectively; the Gs, Ci, Tr and relative content of chlorophyll of flag leaves showed a trend of increasing first and then decreasing, and to their peak at the chromium concentration of 100 mg·kg^-1 in loam soil and clay soil, and at 200 mg·kg^-1 in sandy soil; the WUE increased at first and then decreased in clay soil, showing rising trend in sandy soil and little fluctuation in loam soil. To sum up, there were distinct inhibitions or increasing first and then decreasing trends of photosynthetic indexes of wheat flag leaves during grain-filling stage with chromium stress. While chromium concentration was more than 200 mg·kg^-1, theses stress effects on wheat were showed more and more obviously, such as reduction of root length and root number, decrease of Gs, Ci, Tr and relative content of chlorophyll of flag leaves, as well as the biomass of different organs. Additionally, in the three soil textures, photosynthesis indexes of the flag leaves of wheat during grain-filling stage declined in different degrees with chromium stress, but these decreasing trends were more obvious in sandy soil than that in loam soil and clay soil.