Senescence Mechanisms Aand Vigor Evaluation Of Old Pinus Tabuliformis Carr. In Mountain Tai

This study is set out to explore the adaptation to water stress of Pinus tabulaformis Carr. seedlings and the biological characteristics, photosynthetic characteristics, mineral nutrition, endogenous hormones and membrane permeability of different age of P. tabulaformis. An analytic hierarchy process AHP-fuzzy comprehensive evaluation model had been built to evaluate the vigor of ancient P. tabuliformis in Mountain Tai. The results are showed as follows.1. The growth of roots and needles, biomass distribution and photosynthesis of 4-yearold potted yang trees under continuous drought or waterlogging conditions have showed that: Drought and waterlogging stress inhibit the growth significantly, the biomass of roots, stems and needles decrease with stress time increasing. The descend range of drought stress treatment is larger than flooded stress treatment. The roughness and number of fine roots increase at the early stage of drought stress, but during longer durations of drought stress, the growth vigor gradually falls into a decline with reduced fine roots' number. The plants are easier to die when the stress time is more than 50 days. In duration of water stressing, net photosynthetic rate(Pn), stomatal conductance(Gs), intercellular CO2 concentration(Ci) and transpiration rate(Tr) show a decline continuously, with an observable difference(P<0.05) between treatments. The WP(the soil water potential) as well as the BWP(the branchlet water potential) also decrease compared with the controlled ones. A short-period of drought stress has no significant effect on growth, but chlorosis content descends and needle colour turn yellow under long term of drought stress. Waterlogging stress decrease Gs and Pn, but Ci increase with Pn gradually getting close to zero. The WP and BWP increase, showing a significant difference with control(P<0.05). Moreover, when the waterlogging lasts for more than twenty days, the fine roots begin to decompose and the plants go to die.2. In order to provide scientific basis of the vigor diagnosis and their rejuvenation and management to anti-aging, the growth and physiological diagnosis indices of the young healthy trees and senescence ancient pines were investigated. The annual pine needles from healthy and weak pines with different ages in the Taishan National Park were used as materials. The shoot length, needle length and coarseness, chlorophyll content, membrane permeability, Pn, Tr, Gs, Ci, mineral elements content of C, N, P, K and Mg, abscisic acid(ABA) content of pine needles were measured. The results showed that, comparing with healthy pines, the ancient ones have thinner, shorter needles and weaker photosynthetic capacity, lower growth of shoots, chlorophyll content and light use efficiency. Membrane permeability increases with membrane lipid peroxidation. There are no remarkable changes in P content and increased mineral elements content of C, N, Mg and K in senescing and weak ancient pines. Higher ABA content lead to weakness of vigor. The correlation between morphological changes and physiological indexes are significant. It is summarized that growth and physiological indexes can be used as bases to diagnose the senescence and weakness of ancient pines.3. Fifteen ancient P. tabuliformis trees in Taishan were chosen, and an analytic hierarchy process AHP-fuzzy comprehensive evaluation model was used. Fourteen indexes were studied in total including morphological index, growth index, physiological index, and deadwood states. Field investigations were took in the research along with laboratory experiments. Three of the fourteen indexes were studied in the laboratory including the content of chlorophyll, photosynthetic rate and cell membrane permeability. The rest were investigated in the outside. According to the evaluation results, the vigors of old pines are divided to five grades including healthy(Q?80), mild senescence(80>Q?60), moderate senescence(60>Q?40), Severe senescence(40>Q?20), endangerment(20>Q?0). Results show that all fifteen ancient P. tabuliformis trees have aging characteristics. Compared to healthy trees, two have low grade senescence with only slight decreases in indexes, higher chlorophyll content,photosynthetic rate and cell membrane permeability, luxuriant foliage, intact bark and several dead shoots. Six show moderate senescence with an incomplete canopy, dead branches, and decreased photosynthetic capability. Four are unhealthy with sparse needles, a large number of dead main branches and limbs, and damaged cell membrane permeability. According to the vigor of old P. tabuliformis trees, a series of protection measures were put forward including pest control, setting the fences, spreading fertilizer, pruning and so on.4. According to the resaults of vigor evaluation of old P. tabuliformis, a series of maintenance management and rejuvenation measures has been put forward.