土壤水分含量对虉草幼苗保护酶与渗透调节物质的影响

以虉草幼苗为试材，通过为期50 d的室内盆栽控水试验，按照土壤水分含量设置7个水分梯度：（10±0.5）%、（15±0.5）%、（20±0.5）%、（25±0.5）%、（30±0.5）%、（40±0.5）%（土壤水分饱和）和51%（淹水2 cm），研究了不同土壤水分含量对植物的抗氧化酶活性、丙二醛含量、可溶性蛋白含量的影响。结果表明：（1）土壤水分含量在20%~35%之间时SOD （超氧化物歧化酶）活性较高，低于20%和高于35%时，SOD活性下降，且在不同土壤水分含量下试验50 d的SOD活性均大于试验25 d的。（2） CAT（过氧化氢酶）与POD （过氧化物酶）活性达极显著相关p<0.01，均随土壤水分含量的增加呈先大幅下降后平稳再小幅上升的趋势。（3） MDA （丙二醛）含量与SOD活性趋势相反，随土壤水分含量的增加不断下降，在试验25 d时淹水组略有上升。（4）可溶性蛋白在20%~40%之间时含量较高，植株生长状况较好，在干旱和淹水胁迫条件下可溶性蛋白含量呈下降趋势。由此可见：当虉草幼苗受到干旱等胁迫时，虉草幼苗会开启抗氧化酶系统以保护植株组织，可长时间的胁迫或者胁迫超过其耐受范围（土壤水分含量小于20%或处于土壤水分过饱和淹水条件）就会不同程度的破坏植物的防御系统从而影响其生长发育。

Effects of soil moisture content on antioxidase and osmoregulation substrate content of Phalaris arundinacea seedlings

Soil moisture is an important environmental factor that affects plant growth and physiological metabolism.Under water stress conditions, plants can start the protective enzyme/antioxidant enzyme system and adjust the content of osmotic adjustment substances to respond to the environment.To study the P. arundinaceas' responding mechanism of antioxidant enzyme defencing system to different soil moisture,we selected P. arundinaceas seedlings in good growth condition with well preserved rhizome and consistent germination as test materials.Through 50 days indoor potted water control experiment,we set up seven water gradients of (10±0.5)%、(15±0.5)%、(20±0.5)%、(25±0.5)%、(30±0.5)%、(40±0.5)% (saturated soil moisture) and 51% (2 cm flooded) based on the volumetric water content.The soil moisture content was controlled by manual watering method.It was measured with a HH2 soil moisture meter every day at 20:00 PM,calculated the required moisture volume based on the soil moisture status and quantified the supplement to the set value.The effects of different soil moisture content on malondialdehyde (MDA),superoxide dismutase(SOD),peroxidase(POD),catalase(CAT) and soluble protein content were studied using nitroblue tetrazolium method to measure SOD,guaiacol method to measure POD,CAT was measured by potassium permanganate titration method to measure CAT,Glucosinolates barbituric acid method to measure MDA and Coomassie brilliant blue G-250 dyeing method to measure soluble protein.The results showed as follows:(1) The activity of SOD was higher when the soil moisture content was between 20% and 35%,and when the soil moisture content was below 20% or above 35%,the activity of SOD was decreased.The activities of SOD in 50 days were higher than those in 25 days of the experiment under different soil water content. (2) The activities of CAT and POD were extremely significantly correlated with p<0.01,both of which had a trend with a sharp drop at the beginning,and then becoming steady,then going up slightly with the increase of soil moisture content. (3) The content of MDA was opposite to the trend of SOD,and it was decreased with the increase of soil moisture content.The C7 group (flooding 2 cm) was increased slightly in 25 days of the experiment. (4) The content of soluble protein was higher with the value between 20% and 40%,and the plants were growing well.The soluble protein showed a drop trend under drought or flooding stress conditions.So it can be seen that when the P. arundinaceas seedling was exposed to drought or other stress,it will trigger the antioxidant enzyme system to protect the plant tissue,and the antioxidant enzyme defense system would work through a series of antioxidant protection mechanism to increase plant stress resistance ability,reduce or eliminate the damages to the plants,but the long-term stress or the stress which beyond the plant's tolerance (the soil moisture content is less than 20% or the soil moisture content is oversaturated) will destroy the plant's defense system in various degrees thus affecting the plant's growth and development.