Effects of Low Phosphorus Stress on Leaf Physiological Characteristics of Isatis Indigotica Seedlings
In order to study the effects of low phosphorus stress on leaves of Isatis Indigotica seed-lings,the seeds of I.indigotica were planted in small flower pot based on vermiculite.They were treated with Hoagland nutrient solution in different KH2PO4 concentrations(0 mmol/L、0.05 mmol/L、0.5 mmol/L)for 13 days.Culture conditions were 25 ℃,light intensity was 80 µmol/(m2,s),rela-tive humidity was 75％,light for 12 h/dark for 12 h.The changes in physiological properties were observed.The results showed that 0.5 mmol/L KH2PO4 concentration was the most suitable for the growth of I.indigotica seedlings.When the KH2PO4 concentration was lower than 0.5 mmol/L,with the decrease of KH2PO4 concentration(0.05 mmol/L,0 mmol/L),the physiological characteristics of the leaves of I.indigotica seedlings changed significantly.Compared with the control,respiration rate,net photosynthetic rate,stomatal conductance,intercellular carbon dioxide concentration,total chlorophyll content and water content were decreased by 53.8％and 30.8％,61.3％and 38％,72.3％and 33.1％,45.1％and 27.2％,38.3％and 13.3％,6.7％and 3.7％,respectively.Total soluble sugar content,proline content,electrical conductivity,malondialdehyde(MDA)content,hydrogen perox-ide content and superoxide anion content were increased by 41.6％and 32.4％,54.9％and 24.4％,58.7％and 19.6％,151％and 59.8％,94.1％and 23.5％,78.9％and 47.4％,respectively.The activi-ties of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),ascorbate peroxidase(APX),monodehydroascorbate reductase(MDHAR),dehydroascorbate reductase(DHAR)and glutathione reductase(GR)were increased by 17.2％and 10.9％,57.8％and 42.2％,59％and 15.7％,32.5％and 27％,24.6％and 5.7％,36.1％and 22.7％,45.5％and 33.2％,respectively.Low phosphorus treatment could inhibit photosynthesis and induce osmotic stress on leaves of I.indigoti-ca seedlings.The leaves of I.indigotica seedlings may regulate osmotic pressure by synthesizing osmoprotective substances and clear reactive oxygen species by antioxidant enzymes.
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