Studies On Mitochondria Physiological Changes Of Aluminum-induced Programmed Cell Death Peanut Root Tip

Aluminum(Al) is the limiting factor of crop growth in acid soil, peanut is China's important oil crops, the peanut aluminum toxicity and tolerance mechanisms is unknown. Peanut cultivars LH11( Al-resistant) and R1549 (Al-sensitive) were selected by root elongation experiment, hematoxylin dying and Al content detection of root tip. The mitochondria physiological and changes of Al-induceed programmed cell death(PCD) peanut root were studied with LH11 and R1549 as experimental materials. The results showed that R1549 root tip cell occurred PCD after Al treatment at 100μmol/L for 4d, and two cultivars occurred PCD after 400μmol/L for 4d. Different Al concentrations treatment for 4d, two cultivars root tips Al contents increased with Al concentration increasing. Compared with the control, two cultivars root tips Al contents had very significant differences treated by Al at 100 and 400μmol/L, the differences between two cultivars reached significant level.Al induced peanut root tip mitochondria generating reactive oxygen species(ROS), resulting in lipid peroxidation, it was more serious in R1549 than in LH11. The contents of mitochondria O₂^·-, H₂O₂ and MDA from two cultivars root tips for 4d Al treatment increased along with Al concentration increasing, that of R1549 was higher than that of LH11 under different Al concentration treatments. The difference of two cultivars mitochondria O₂^·-, H₂O₂ and MDA contents was very significant at 100μmol/L Al treatment, but that was not significant at 400μmol/L. It is suggested lipid peroxidation is one of reasons of Al toxicity.The root tips mitochondrial SOD and CAT activity of two cultivars increased firstly, than decreased after Al treatment, that of LH11 and R1549 reached the peak at 100μmol/L and at 20μmol/L, respectively. The root tips mitochondrial activity of SOD and CAT, of LH11 was higher than that of R1549 at 100 and 400μmol/L Al treatment, the difference was significant. The root tips mitochondrial POD activity increased with Al concentration increasing, that of LH11 was significantly higher than that of R1549 at 400μmol/L Al treatment. With Al treatment concentration increasing, the root tips mitochondrial APX activity of two cultivars decreased, but that of LH11 was higher than that of R1549, there was very significant difference between two cultivars at 0, 20, and 100μmol/L Al treatment except for 400μmol/L, it was not significant between different Al concentration treatments in same peatnut cultivar. The root tips mitochondrial GSH-Px activity of LH11 increased firstly, than decreased, but that of R1549 decreased. There was very significant difference between two cultivars GSH-Px activity at 100μmol/L, but it was not significant at 400μmol/L. With Al concentration increasing, two cultivars root tip mitochondrial Ca²⁺-ATPase activity and Ca²⁺ content decreased, that of R1549 decreased fastly, but there was not significant difference between two cultivars.After Al treatment, root tips mitochondrial permeability transition pore (MPTP) andΔψundergone distinct changes. With Al concentration increasing, mitochondrial optical density continued to drop, MPTP enlarged, mitochondriaΔψdecreased significantly, mitochondria Cyt c content reduced. It was more obvious in R1549 than in LH11.To sum up, with low Al concentration treatment, plant was stimulated, reactive oxygen species was produced, plant growth was inhibited. Al-resistant plant had high antioxidant enzyme activity, could eliminate Al-induced ROS and reduce damage degree, but Al-sensitive plant produced more ROS after Al stress, had low ROS removal ability, was easy to be harmed. Under high Al concentration treatment, ROS produce accelerated, removal ability of ROS clearance system decreased, mitochondrial ROS concentration was higher, caused severe lipid peroxidation, induced mitochondrial permeability transition pore opening, impacted cross-mitochondrial membrane Ca²⁺ transit system so that cytoplasm Ca²⁺ concentration increased, in the meanwile, cytochrome c released into the cytoplasm, activated cysteine protease enzyme or others, and induced root tip cells produceing PCD, root growth was subject to inhibit.