| In this paper, we investigated the canopy seed bank and the composition of soil seed bank of Glycyrrhiza uralensis in arid areas of Yanchi in Ningxia; Researched the influence of sulfuric acid pretreatment with different illumination and temperature, water stress on the seeds germination; Determinated the growths physical-and photosynthesis characteristics of seedlings under different conditions of water stress; Investigated the characteristics of initiation updated seedling and its relationship with the overground part, as well as the proportion of health and initiation regeneration seedlings. On the basis of revealing about the key obstacle sectors of natural regeneration in wild Glycyrrhiza uralensis and its population regeneration, we made a in-depth study of the main way to the community regeneration of Glycyrrhiza uralensis, not only can provide theoretical basis on effective protection and sustainable utilization of wild Glycyrrhiza uralensis in China, but also is of great significance to restore vegetation in sandy area and prevent desertification. The main results were as follows:1. The plant density of the sample survey was1963.06to7111.46plants/mu, the density of canopy seed bank was6.25to22.49grain/m2, which has only24%of intact seeds with the potential renewability. There were14species germinated in soil seed bank, belong to8families, per unit area of soil seed bank density is1733grains, given rise to seed regeneration difficulties, combined with the kinds of factors such as seed coat limiting, there was no seed establish seedlings in soil seed banks.2.Under the natural conditions of wild Glycyrrhiza uralensis seed germination rate is extremely low,. Glycyrrhiza uralensis seeds can germinate in10～40℃, the suitable germination condition is20～30℃, lighting10h·d-1. The pretreatment of concentrated sulfuric acid significantly increased the germination rate about5.6times. Lighting has a promoting effect of seed germination, the pretreatment of sulfuric acid reducing its dependence of light. Water stress can delay seed germination process, inhibit the germination of untreated seeds, appropriate drought stress (5%to20%PEG) can enhance the vigor index after breaking seed coat limit.3. As the drought stress proceeding, the morphological characteristics of the seedlings turn normal into yellow leaves and even death, mild stress is beneficial to root growth. With the increasing of drought stress, the content of proline increased continuously. The content of chlorophyll, MDA, SODn POD and root activities were increasing firstly and decreased then. We can concluded that the growth of Glycyrrhiza uralensis seedlings were negatively influenced by drought stress, but its own growth and physiological regulation substances could adjust the seedlings themselves to avoid water drought harms, and the drought tolerance of Glycyrrhiza uralensis seedlings was limited with the concentration of PEG was under15%(-0.40MPa water potential).4.Drought stress can not only change the Glycyrrhiza uralensis leaf photosynthetic rate in different time throughout the day, but also change its daily change rule. Photosynthetic noon break phenomenon is obvious, and the main cause of it is stomatal factors. In order to adapt to water stress, the main limiting factor the photosynthesis in many transformations between stomatal limitation and the stomatal limitation. Under the stress of5%10%PEQ Glycyrrhiza uralensis can significantly decreasing photosynthetic rate to increase its water use to adapt to drought, but this adaptation were destroyed under high stress.5.Wild Glycyrrhiza uralensis seedlings accounted for14.95%, with85.05%sprouting seedlings, the natural regeneration is given priority to initiation update, supplemented by seed generation. The amount seed output was more produced by tertiary lateral root sprouted plants, its vertical rhizome length was7.21cm.6.1n arid areas of middle Ningxia, the important factors for wild Glycyrrhiza uralensis seed generation difficulties were the lower seed production, less of seeds with the potential renewability and high hard seeds rate; wild Glycyrrhiza uralensis seed can tolerate low temperature, was sensitive to water stress, and linght has a promoting effect on its germination; it has strong ability of drought tolerance, can be adjusted by adjusting the internal physiological substances promote the growth of licorice root to absorb moisture under moderate water stress. Powerful initiation ability can guarantee the community maintain and stability, which is an important way of Glycyrrhiza uralensis to breakthrough the key obstacle sectors of natural regeneration, at the same time complementary with seed regeneration to improve and maintain the genetic diversity of population. |
