Response Mechanism Of Biomass Allocation And Root Plasticity Of Chinese Fir To Heterogeneous Phosphorus Supply

Phosphorus is one of essential nutrients for growth and development of plants, and phosphorus deficiency is the important factor to limit plantation production at present. The strong chemical fixed effect to phosphorus in acidic soil of the south lead to phosphorus scarce in southern forest soil. And there are lots of reserved phosphorus which plants can't use in soil, so that total phosphorus the in soil is high and available phosphorus which trees can absorb is low, which showed conflict of "genetics phosphorus deficiency" in trees. Roots grow in soil which developed long-term adaptation to terrestrial environment, through long-term evolution. Roots form a variety of functions as plant roots, including the important adaptive shape, which improve phosphorus effective absorption through development and the evolutionary process. Therefore it is the key to reveal forest root efficient to find the plasticity of the characteristics and to improve phosphorus utilization efficiency, which has important theoretical and practical significance to fully exploit the hard dissolved phosphorus in southern forest soil.Chinese fir is one of the most important tree species in the south of China, with fast growth, high yield, and fine material quality. In recent years, Chinese fir's afforestation area was expanding constantly, broad-leaved forestry area sharp cutoff. Continuous cultivation for generations declined the wood land's productivity, seriously influenced the sustainable management of Chinese fir. In nature world, soil nutrient is highly heterogeneous, the nutrient content is quite different in several meters even a few centimeters ranges. In long-term natural selection conditions, in order to furthest gain soil resources, towards high soil nutrient space heterogeneity, plant forms foraging mechanisms, such as form plasticity, physiological plasticity and mycorrhiza plasticity. Many roots increase a large number in nutrient rich plaques, different plants have different ways of increase, and it is influenced by the size of plaques, the concentration of nutrient, the kind of nutrition elements and the gross of nutrient..In view of this, according to the principles and methods of plant nutrition genetics morphology and root biology, considering Chinese fir half-sib seedlings as the research object, by constructing potting simulation tests which processed under 21 kinds of heterogeneous phosphorus supply, measuring Chinese fir's root morphology index and phosphorus uptake and use efficiency in the heterogeneous phosphorus condition, analyzing index difference between different treatments of the Chinese fir, this article discusses index in heterogeneous phosphorus stress condition of morphology adaptation mechanism. It provides scientific basis of using heterogeneous phosphorus stress from the morphology of Chinese fir. The main research results were as follows:1. There was significantly different between root biomass under heterogeneous phosphorus supply. In root room 1 with moderate content (12mg/kg) under phosphorus heterogeneous supply, root biomass of Chinese fir in rich phosphorus patch was higher than that in low phosphorus patch. As the heterogeneity intensified, Chinese fir tend to grow in rich phosphorus patch, but root biomass of the whole plant showed degressive change as phosphorus in growth medium increased.2. Root shoot ratio was different under heterogeneous phosphorus supply. In Room 1 with no P supply under heterogeneous P supply, root shoot ratio decreased first and then increased as the heterogeneity amplified. In root room 1 with moderate content (12mg/kg) under phosphorus heterogeneous supply, root shoot ratio of Chinese fir was inversely proportional to phosphorus content.3.In low P conditions, phosphorus utilization efficiency of roots of Chinese fir showed descending order with the amount of phosphorus increasing; In P sufficient conditions, phosphorus use efficiency of roots of Chinese fir also showed the same trend. In low P conditions, phosphorus utilization efficiency of leaves showed the first increase and then sharp drop with the total phosphorus increasing. From phosphorus use efficiency in the whole plant, maximum phosphorus use efficiency of whole-plant was in treatment P4 + P8, with the minimum in treatment P12 + P4.4.There was significantly different of root morphological characteristics of Chinese fir under heterogeneous phosphorus supply. In Room 1 with12mg/kg P supply under heterogeneous P supply, root morphological plasticity of Chinese fir roots was quite different. Root length, root surface area and root volume of Chinese fir in the phosphorus-rich patch were all greater than those in the phosphorus-poor patch, but root length, root surface area, root volume of whole plant decreased as phosphorus content increased.5. Under homogeneous phosphorus supply, total phosphorus content had significant effect on root growth. Total root length decreased as phosphorus content increased, so did that in root surface area and root volume.