钙对花生（Arachis hypogaea L.）幼苗生长、活性氧积累和光抑制程度的影响

Abstract

Peanut( Arachis hypogaea L.) is one of the most important oil-crops in the world,and Ca is a critical nutrient for this crop to achieve high yields. Severe Ca deficiency in soil could result in unfilled peanut pods and caused decrease in yield. Ca2+acts as a regulator of many physiological and biochemical processes in response to abiotic stresses in plants.Transient elevation of free Ca2+in the cytoplast was detected in plants in response to various stresses,such as high temperature,cold injury,drought and salt stress. The fact that Ca2+improves plant resistance to stresses is that the Ca2+treated plants could maintain a high photosynthetic rate under stress condition. Light-induced Ca2+influx into chloroplasts not only influences the cytosolic concentration of free Ca2+but also regulates the enzymatic processes inside the chloroplast.Effects of Ca2+on peanut plant growth and development,yield and reactive oxygen species( ROS) accumulation have been reported. However, the effects of different Ca2+concentrations on peanut seedling growth, ROS accumulation and photoinhibition have not been studied in detail. In the present work,in order to investigate the effects of calcium on peanutseedling growth,Huayu 22 was used and cultured in modified Hoagland' s solutions with 0,6 and 12 mmol / L Ca2+,respectively( abbreviated as CK,C6 and C12). After 20 d treatment,Ca2+content in CK,C6 and C12 seedlings was measured. The results showed that Ca2+content in roots and leaves of CK seedlings was the lowest and that in C12 seedlings was the highest. The results showed that Ca2+promoted the growth and fresh weight accumulation of peanut seedlings. The root to shoot ratio was decreased when plants were grown in 6 and 12 mmol / L Ca2+to compare with the control. Ca2+improved the enzymatic activity in root and the accumulation of ROS in both leaves and roots was reduced under normal culture conditions. It seems that C12 seedlings were in a better physiological state than CK and C6. When functional leaves were exposed to high temperature( 42 ℃) and high irradiance( 1200 μmol m-2s-1),C6 and C12 leaves accumulated less hydrogen peroxide( H2O2) and superoxide anion radical( O-2),maintained higher maximal photochemical efficiency of photosystem Ⅱ( PSⅡ)( Fv / Fm) and lower 1- q P to compare with CK. Furthermore,C12 seedlings accumulated lower concentration of H2O2 and O-2and kept higher Fv / Fm than C6 seedlings. These results demonstrated that Ca2+could alleviate photoinhibition and the accumulation of ROS under stress condition. In addition,compared with those of CK,the activities of some ROS scavenging enzymes [e.g. superoxide dismutase( SOD),ascorbate peroxidase( APX) and catalase( CAT) ]and the contents of some osmoregulation substances [e. g. proline( Pro),soluble sugar and ascorbate acid( As A) ] were significantly higher in C6 and C12 leaves,while the content of malonaldehyde( MDA) was significant lower in C6 and C12 leaves. Together,these results indicated that Ca2+could protect peanut thylakoid membrane from damage directly or indirectly under stress condition by increasing activities of ROS scavenging enzymes and the contents of some osmoregulation substances.