钾镁胁迫对橡胶幼苗叶片物质成分影响的FTIR表征

养分亏缺是作物产量和质量提升的重要限制因子。我国砖红壤植胶区钾、镁缺乏及其低的有效性长期制约天然橡胶的产、质量。以“热研7-33-97”橡胶幼苗为研究对象，利用傅里叶变换红外光谱（FTIR）对钾、镁胁迫下橡胶树叶片物质组成特征进行研究，分析不同钾、镁胁迫条件下叶片红外光谱图谱特征峰的变化及其差异，探讨钾、镁胁迫对叶片物质成分和结构的影响，以期为钾镁缺乏影响橡胶树生长与生理代谢的机理研究提供参考。结果表明：（1）缺钾条件下，1 554，1 519和1 075 cm-1处的吸收峰缺失，表明橡胶叶片中蛋白质酰胺Ⅱ带、酚类物质、碳水化合物的化学结构受到破坏，并且其他特征峰吸光度与正常处理相比均有不同程度的升高，表明缺钾造成蛋白质、碳水化合物等物质在叶片中大量积累，物质转运效率降低；（2）缺镁条件下，1 554 cm-1处吸收峰向高频方向位移了6 cm-1，说明缺镁造成蛋白质酰胺Ⅱ带的结构发生改变，同时，1 550~1 350 cm-1波数范围内吸收峰相对吸光度明显下降，说明缺镁降低了细胞壁多糖以及含油脂化合物的含量，且该波数范围内的三个吸收峰较其他吸收峰变化敏感，表明该波段可以较好地指示橡胶叶片镁营养状况；（3）钾镁同时缺乏条件下，各吸收峰的相对吸光度和强度明显减弱，1 554，1 519和1 075 cm-1处的吸收峰缺失，说明蛋白质酰胺Ⅱ带、酚类物质、碳水化合物的化学结构受到破坏，1 057 cm-1处吸收峰向高频方向位移了11 cm-1，表明橡胶叶片中果胶类多糖分子结构发生了变化。综上所述，缺钾造成橡胶叶片蛋白质、糖类物质的含量的大量积累，缺镁造成叶片细胞壁多糖和油脂化合物下降，而钾镁同时缺乏时蛋白质、脂类、糖类物质等物质含量均明显下降。研究表明，使用FTIR技术对养分缺乏下的橡胶叶片物质成分定性分析具有一定的可行性，同时可为橡胶钾、镁营养生理代谢的机制研究提供新的思路和方法。

FTIR Spectroscopic Characterization of Material Composition in Leaf of Hevea Brasiliensis Seedlings Under Potassium and Magnesium Deficiency

Nutrient deficiency is a vital limiting factor for crop yield and quality improvement.It has restricted the yield and quality of natural rubber for a long time because of the depletion of soil potassium(K)and magnesium(Mg)and their low plant availability in the Laterite soil of rubber plantations,South China.Rubber seedlings of“CATAS 7-33-97”was chosen as test material,the material composition characteristics of rubber leaves under K and Mg deficiency were studied by Fourier transform infrared spectroscopy(FTIR).The changes and differences of FTIR_characteristic peaks of leaves were analyzed,and the material compositions and structures were discussed.It would provide some physiological evidence of rubber plants subjected to K and Mg deficiency stress.The results showed that:(1)the characteristic peaks of 1554,1519 and 1075 cm^-1 disappeared due to K deficiency,implying that the structure of amideⅡband,phenolic compounds and carbohydrate were broken.The relative absorbance of all characteristic peaks was increased compared with normal treatments,suggesting that protein and carbohydrate were accumulated in leaf to reduce their translocation efficiency.(2)The absorption peak at 1554 cm^-1 shifted 6 cm^-1 to high frequency as 1560 cm^-1 when the plant was subject to Mg deficiency,which indicated that the structure of the protein amideⅡband was changed.Meanwhile,Mg deficiency decreased the relative absorbance in the range of 1550~1350 cm^-1,implying that Mg deficiency decreased the contents of polysaccharides and lipid compounds of the leaf cell wall.The three absorption peaks in the wave number of 1550~1350 cm^-1 were more sensitive to Mg deficiency than other absorption peaks,indicating that the wave band could better represent the magnesium nutrition status of rubber plant leaves.(3)The relative absorbance and intensity of each absorption peak decreased obviously at both K and Mg deficiency.Absorption peaks at 1554,1519 and 1075 cm^-1 disappeared similar to that K deficiency,which indicated that the chemical structure of protein amideⅡband,phenols and carbohydrates was destroyed.Meanwhile,the absorption peak of 1057 cm^-1 shifted to the high frequency direction by 11 cm^-1 to 1068 cm^-1,implying the molecular structure of pectin polysaccharides changed in rubber leaves.In conclusion,K deficiency caused a large accumulation of protein and carbohydrates in rubber leaves,and magnesium deficiency caused the decrease of polysaccharide and lipid compounds in the leaf cell wall.However,the contents of protein,lipid and carbohydrates decreased significantly when the plant was subjected to both K and Mg deficiency.The results showed that FTIR technology was feasible for qualitative analysis of the material components of rubber leaves under nutrient deficiency and could provide new ideas and methods for studying the mechanism of K and Mg nutrition and physiological metabolism of the rubber trees.