过量锰处理对苗期柱花草生长及抗氧化酶活性的影响

以2份柱花草基因型(TF210和TF226)为材料,分析过量锰处理对苗期柱花草生长、叶绿素浓度(SPAD)、最大光化学效率(F_v/F_m)、超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性的影响,探究柱花草中潜在的耐锰机制。结果表明,过量锰(400 μmol·L^-1)处理显著抑制了柱花草基因型TF210地上部和根系的生长、降低了其叶片SPAD和F_v/F_m值,但对TF226生长影响不明显,说明TF226为耐锰基因型,而TF210为锰敏感基因型。虽然过量锰处理增加了两个柱花草基因型组织锰含量,但TF226地上部和根部的锰含量显著低于TF210,暗示在过量锰处理下,TF226积累了较少的组织锰含量。过量锰处理显著增加了两个基因型叶片SOD活性,但仅增加了TF226叶片POD和CAT活性,并且在过量锰处理下,TF226叶片SOD、POD和CAT活性值均高于TF210。以上结果说明维持根系生长、降低组织锰含量和提高抗氧化酶活性是苗期柱花草TF226耐锰的生理机制。研究结果为探索柱花草耐锰机理及耐锰柱花草品种改良提供了理论依据及种质材料。

Effects of excess manganese toxicity on growth and antioxidant enzyme activity in Stylosanthes guianensis seedlings

The aim of this study was to investigate the potential mechanisms underlying stylo (Stylosanthes guianensis) tolerance to high Mn levels. The growth responses and Mn tolerance in stylo were assessed in two stylo genotypes, TF210 and TF226 grown hydroponically. Plant dry weight, root growth parameters, chlorophyll concentration (soil plant analyzer development, SPAD), maximum photochemical efficiency (F_v/F_m) as well as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were measured under two Mn levels. Results showed that significant decreases in shoots and roots growth, SPAD and F_v/F_m values were observed in stylo genotype TF210 compared to TF226 under 400 μmol·L^-1 MnSO₄ treatment, suggesting that TF226 was a more Mn-tolerant genotype compared to TF210. Although Mn content in shoots and roots of both genotypes was increased by high Mn treatment, Mn content in TF226 was lower than that in TF210, suggesting that less Mn was accumulated in TF226 compared to TF210. Furthermore, SOD, POD and CAT activities in leaves of TF226 were significantly increased under high Mn treatment, while only SOD activity in leaves of TF210 was increased by high Mn. Activities of the three tested enzymes in TF226 were higher than those in TF210 under high Mn. These results suggest that regulations of root growth, Mn accumulation and antioxidant enzyme activities might be the adaptive mechanisms of stylo tolerance to Mn toxicity. The present study not only provides theoretical basis for dissecting Mn tolerant mechanisms, but also providing germplasm resources for improving adaptation to Mn toxicity in stylo.