Effects Of Soil Compaction Stress On Ascorbate-glutathione Cycle And Root Respiration Of Cucumber

Soil compaction stress, one of the common phenomenon in the soil of arid and semi-arid area and protected field, has become one problem effecting on the growth and development of crops. Soil compaction has adverse effects on the growth, yield and quality of the crops and also decreases soil quality, threats the sustainable development of agriculture. It will provide preference for sustainable utilization of soil in arid and semi-arid area and protected field ,to study the effects of soil compaction stress on physiological metabolism of crops and explorate the effect mechanism soil compaction stress on crops .Taking the cucumber'Jinchun 4'as the tested materials, the effects of ascorbate- glutathione cycle and respiratory metbolism pathway of cucumber were studied in the soil compaction stress.There were two levels of the soil bulk density, 1.2 and 1.5 g/cm^-3 ,the results showed:1. The peroxidation, accumulation of reactive oxygen species, cell membrane was damaged,hydrogen peroxide(H2O2)and malondialdehyde(MDA)contents increased in cumumber plants under the soil compaction stress ,At the same time,The ascorbate- glutathione cycle was start in soil compactinn stress, glutathione(GSH)contents decreased intensively while dehydroascorbate(DHA)and oxidized glutathione (GSSG) contents and GSSG/GSH ratio largely increased,But GSSG+GSH have small change. Concom- itantly,ascorbate peroxidase(APx), monodehydroascorbate reductase (MDHAR), de- hydroascorbate reductase (DHAR) and glutathione reductase (GR)activities in plant have increased.2. The soil compaction stress occurred the product of glycolysis for pyruvate cumulate was decreased and the process of the aerobic respiration was inhibited, anaerobic respiration to strengthen in cumumber roots:The main enzymes of aerobic respiration for the succinic dehydrogenase(SDH),malate dehydrogenase(MDH)and isocitric dehydrogenase(IDH)activity was weaker and the main metabolites for malate contents was decrease significantly under soil compaction stress. The main enzymes of anaerobic respiration for alcohol dehydrogenase(ADH),lactate dehydrogenase(LDH)and pyruvate decarboxylase(PDC)activity was increase and the main metabolites for alcohol, acetaldehyde, lactate acid contents was increase.