Studies On The Biomass Dynamic Characteristics,the Anatomical Structures And Physiological Characteristics Of Zostera Marina L.

Zostera marina L. is a kind of seagrasses that widely distribute in the sea of Liaoning Province, Shandong Province and Hebei Province. Z. marina can complete the entire life history in the high salinity of sea water, so it is considered as the perfect material to study the mechanism of salt tolerance in higher plants. In this paper, the biomass of Z. marina in Qingdao Huiquan bay was investigated to reveal the seasonal allocation rules of the Z. marina. Furthermore, the effect on the anatomical structures of Z. marina and the physiological effects of Z. marina in different salinity were studied to discuss the physiological mechanisms of salt-tolerance of Z. marina.1. The monthly dynamic characteristics of biomass of Z. marina in Qingdao Huiquan bayThe continuous investigation of biomass of the Z. marina L in Qingdao Huiquan bay has been proposed from 2010 to 2011. The analysis of the monthly variation date showed that the biomass underwent a process of reduction to an increase from May to April and the maximum of biomass appeared in May. The population characteristics has changed obviously from June to October,with the average height decreasing significantly and the population density declining rapidly. Furthermore the biomass has declined markedly and accumulation rate of biomass is negative. After November the biomass has a slight increased, biomass accumulated less efficient. The biomass entered the fast growing period in the early of spring.The plant height and the population density has increased. The biomass accumulated rapidly. The community AGR (absolute growth rate) is positive from November to April of next year; and the AGR is negative from May to October. The RGR (relative growth rate) of Z. marinaL in May to October are negative, while November to April of next year the value of RGR is positive.2. The observation of the anatomical structures of Z. marina The observation of frozen section and scanning electron microscope from Z. marina in different salinity (17.5, 35, 52.5) artificial seawater (ASW) showed that the outermost of the root epidermis is larger parenchyma cells which structure is broken. Next to the broken larger parenchyma cells is small sclerenchymatous cell which arranged closely. The center of the root is vascular bundle. There are many large aerenchymas between the epidermis and vascular bundle in root. The salinity treatment affects the formation of the aerenchyma to some extent. The outermost broken parenchyma cells are presumed that it only existing in seedlings of Z.marina, and its functions need to be studied further. The epidermis of shoot of Z. marina is a layer of small cells which closely arranged. The center of the shoot is vascular bundle, between the vascular bundle and epidermal there is parenchyma, which was distributed many aerenchymas. The scanning electron microscope of the shoot of Z. marina in 52.5‰ASW treated show that there is some hyperplasia surrounded by the shoot in which distributed large aerenchyma, and the structure of the hyperplasia are very similar to leaves. There are functional epidermal cells in shoot, suggesting that young shoot also has some absorption function. There is only a layer of small and dense epidermal cells of the leaf. The mesophyll consisted of many large parenchyma cells. There are a lot of large aerenchymas and some leaf vein in the leaf. The aerenchyma of the leaf is constituted of the regular arrangement parenchyma cells which look like a flowers ring. About every four aerenchyma there is a leaf vein which is constructed by parenchyma cells and collenchyma cells. The leaf epidermal cell wall is thickening with salinity increasing. The chloroplast structure is most complete in normal sea water salinity. It was worse impacted by hypotonic and hypertonic. The certain salinity can lead in the mitochondria's structural damage.3. The physiological response of Z. marina to salt stress Under laboratory conditions the limiting salinity of Z. marina was measured. Thephysiological effects in different salinity gradients (17.5, 35, 52.5) were identified and the physiological mechanisms of sea halophyte were discussed. The results showed that the limiting salinity of Z. marina was 61.25. The respiration rate of Z. marina L has increased and the photosynthetic rate has decreased slightly with the increasing salinity. The content of Na⁺, Ca²⁺, organic osmoticas, such as proline, free amino acids, organic acids, soluble sugars, MDA increased with increasing salinity. The osmotic potential also increased with increasing salinity. However, the contents of K ⁺ were decreased with increasing salinity and water content was no significant difference under salinity gradients treatment. The content of Na⁺ is leaf> root> stem, and the K ⁺ / Na ⁺ ratio and Ca^{2 +} / Na ⁺ ratios were significantly lower. The ASK, Na of shoot, stems and leaves was gradually increased, but the increasing of ASCa, Na was not significant...