水稻/再力花单、间作系统中作物对镉胁迫的叶绿素荧光响应及镉积累特征
Responses of PSⅡ chlorophyll fluorescence under Cd stress and characteristics of Cd accumulation in Thalia dealbata and rice mono-and inter-cropping systems
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摘要: 【目的】研究水稻 Oryza sativa 和再力花 Thalia dealbata 在单、间作模式下叶片光系统Ⅱ(PSⅡ)对镉(Cd)胁迫的响应以及2种植物的镉吸收积累特征．【方法】使用PAM-2500便携式荧光仪测定不同处理下植物叶片的叶绿素荧光参数．采用 HNO3-HClO4 湿法消解处理样品，并用石墨炉原子吸收法测定不同处理下植物组织Cd的含量．【结果和结论】随Cd浓度增加，水稻 Fv/Fm、YII、qP 和 rETR 显著下降，qN 和 NPQ 显著升高，表明PSⅡ光合活性受到Cd胁迫抑制，接受光强过高的情况下叶片通过增加热耗散来消耗过剩的光能以减弱PSⅡ的光抑制．YNO 显著升高，表明高浓度Cd处理对水稻的PSⅡ造成损害，导致光反应中心吸收的光量子以非调节性能量耗散的份额增加．而相同浓度处理下再力花的 Fv/Fm、YII、qP、rETR 降幅明显低于水稻，同时叶片 YNPQ 升高，但 YNO 稳定在较低水平，表明其调节性能量耗散机制发挥主要作用，PSⅡ光合活性受抑制程度相对较低．间作下水稻的根、茎、叶Cd含量低于单作．同一Cd浓度的间作模式下，再力花Cd积累总量显著高于水稻．以上结果表明，再力花对高浓度Cd胁迫有较强的耐受性，与水稻间作能降低水稻植株Cd含量．Abstract: 【Objective】 An experiment was conducted to ascertain the effects of Cd stress on the PSⅡ chlorophyll fluorescence parameters in leaves of Thalia dealbata and rice in both the intercropping and mono-cropping systems as well as the uptake and accumulation characteristics of Cd by T. dealbata and rice. 【Method】 The chlorophyll fluorescence parameters in the leaves under different treatments were measured with PAM-2100 Chlorophyll Fluorometer. The contents of Cd in the samples from different treatments were determined using Graphite Furnace Atomic Absorption Spectrometry after wet ashing with HNO3-HClO4.【Result and conclusion】The Fv/FmYII, qP and rETR of the rice decreased with the elevated Cd content in the soil while the qN, NPQ and YNPQ of the rice showed an opposite trend, indicating that the PSⅡ photosynthetic activity was inhibited under Cd stress, while the proportion of the heat dissipation increased to alleviate the photoinhibition of PSⅡ under the condition of excessive light interception. The YNO of the rice increased in a high level of Cd content, which indicated that the higher level of Cd stress induced damage to PSⅡ reaction centres, and the quantum yield of non-regulated energy dissipation increased to a higher level under conditions of excessive light energy. The decrease of Fv/FmYII, qP and rETR in T. dealbata were much lower than those in rice with the same level of Cd stress. With a higher level of Cd stress, the YNPQ)in T. dealbata increased significantly while the variation of YNO) in T. dealbata was not obvious, which suggested that the regulatory energy dissipation mechanism played a major role in the protection of photosynthetic apparatus in Cd stress. At the same level of Cd content in soil, the sequence of Cd content was root > stem > leaf in the rice and stem > root and leaf in T. dealbata. The Cd contents in the root, stem and leaf of rice in the intercropping system were, respectively, lower than those in the monoculture system. The amount of Cd uptake by T. dealbata was significantly higher than that of rice with the same level of Cd treatment. All these results suggested that the photosystem II reaction center of T. dealbata had a higher tolerance to the Cd stress, and the Cd content of rice in intercropping system could be reduced.
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