Studies On Sensitivity Of Ethrel Injury To Rubber Seedlings In Different Growth Stages

Bud grafting is the main implant material of rubber tree (Hevea brasiliensis). Rootstock is a important component part of rubber budding tree and has influenced scion yield. At present, the ethrel stimulated tapping system is a primary tapping system. So rootstocks maybe influence characters of the ethrel stimulated tapping. Sensitivity to ethrel injury in different growth periods of rubber seedling is studied. It's a basic to further research relation between rootstock and ethrel stimulated tapping, to put forward good methods of scion breeding which benefits ethrel stimulation tapping. This has important significance to fulfill sustainable development of rubber tree under the condition of ethrel simulation.This experiment observes that injury to rubber seedlings and characteristic of physiology and biochemistry under different concentration of ethrel stress in different growth periods after ethrel stress. The mechanism of different sensitivity to ethrel of rubber seedlings is studied. The preliminary results are as follows:1. When top cluster leaves are treated by exogenous ethrel, leaves in different phenological-phase have no obvious effect on injuring; different rubber seedlings treated by exogenous ethrel would suffer injury to different extent.2. Choice methods of young seedlings that are non-sensitivity to ethrel injury: Treat the parts below the first cluster leaves with 0.5% ethrel, 24 hours later, pick out the seedlings which suffer obvious injury– sensitive seedlings; Treat with 1.5% ethrel, after 36 hours, pick out the seedlings which has no obvious injury– non-sensitive seedling.3. Compared with mini-seedlings in the stable-period, young seedlings have more obvious appearance symptom when injuried by ethrel. Treated by exogenous ethrel with low concentration, the sensitivity difference between young seedling and mini-seedling (the stable-period) is not obvious; treaded by exogenous ethrel with high concentration, the sensitivity difference between young seedling and mini-seedling (the stable-period) is greatly obvious.4. The survival rate of young seedlings which suffer ethrel injury is greatly obvious higher than that of mini-seedling.5. When choosing the materials that have different sensitivity to ethrel injury, it's more suitable during young seedling than in mini-seedling. 6. To the young seedlings that have different sensitivity to ethrel injury, the and O2- production rate of sensitive seedlings are higher than that of non-sensitive seedlings, and membrane permeability and MAD (malondiadehyde) content are obvious; the activity of SOD, CAT and APX of sensitive seedlings are lower than non-sensitive seedlings, and the activity of SOD is great obvious, the activity of APX is obvious.7. The mechanism of young seedlings'different ethrel injury sensitivity is probably that after ethrel injury, sensitive young seedlings produce active oxygen more quickly than that of non-sensitive young seedling, and the enzyme activity of protective system (SOD, CAT & APX) is low.8. The difference of sensitivity to ethrel injury among most RRIM600 rubber seedlings is steady-going.