珍稀药用植物白及光合与蒸腾生理生态及抗旱特性

以珍稀濒危药用植物白及(Bletilla striata)叶片为研究对象,应用Li-6400XT便携式光合仪分别在晴天和阴天进行光合生理生态特性研究。结果显示晴天Gs、Pn、Tr日变化呈现双峰型,阴天为单峰型;光合-蒸腾具有极显著线性正相关关系与良好的线性耦合关系(晴天和阴天的相关系数分别为0.883^**、0.954^**,回归直线斜率分别为2.38、3.78);PAR-Pn与PAR-Tr、Tl-Pn与Tl-Tr、Gs-Pn与Gs-Tr 的回归直线形态非常相似,除晴天Tl与Pn外,其余两两相关关系均达到了显著水平;PAR、Tl和Gs三个因子与Pn、Tr均表现为正相关关系,其中Gs是调控Pn与Tr的最主要因子。进行聚乙二醇6000(PEG6000) 渗透胁迫实验以评价白及抗旱能力,分析不同质量分数PEG6000(0、5、20、40、60g/L)下的白及幼苗叶绿素含量、叶片含水量、相对电导率3个生理指标,结果表明叶绿素含量与与胁迫浓度呈负相关(R²=0.7854),随着PEG质量分数的增加,叶片的叶绿素含量持续显著下降;叶片含水量与胁迫浓度呈负相关(R²=0.9936);相对电导率与与胁迫浓度呈正相关(R²=0.8755),相对电导率会随着PEG质量分数的增加而显著增加。试验结果综合分析显示白及为耐荫植物,抗旱能力不强。白及进行人工栽培应适当遮阴保持土壤与空气湿度。

Photosynthetic physiological ecology characteristics of rare medicinal plants Bletilla striata

The genus Bletilla, composting about six species, is endemic to Asia with a distribution pattern from N Myanmar and Indochina through China to Japan. The usage of the plants of Bletilla, mainly Bletilla striata (Thunb.) Reichb. f., includes art (Chinese painting and writing), the production of porcelain, and medicine, as well as vegetable dyes for dyeing cloth in some minority people in Guizhou and Yunnan Province, China. Those species are also commonly used as a horticultural subject covering both indoors and out cultivation in North American and European areas. As the traditional herb medicine using more than 1500 years, pseudobulbs of Bletilla have been widely used in Eastern Asian countries to treat alimentary canal mucosal damage, ulcer, bleeding, bruises and burns. The pseudobulbs also show antibacterial, anti-inflammatory, antiphlogistic and demulcent properties, and thus use in treating pneumonophthisis, pneumonorrhagia, tuberculosis and haemorrhage of the stomach or lung. Moreover, it is suggested that cationic polysaccharide from Bletilla strata can serve as a non-viral nucleotide drug delivery vehicle for oligonucleoide or siRNA targeting to immunology system. Apparently, there is a huge potential demand for the pseudobulbs of Bletilla in future. At present, the cultivation of Bletilla is only limited to the temperature areas of North America and Europe for the horticultural purpose, and the using of pseudobulbs of Bletilla for other purpose especially for medicinal purpose is basically based on wild resources. Undoubtedly, the wild resource of Bletilla will rapidly decrease in Eastern Asian Countries due to over collections as well as habitat destruction and fragmentation. The conflict between the great market demand for the pseudobulbs of Bletilla and the decreased wild resource has necessitated the breeding of cultivars for high yields, high concentrations of active components, and high resistance to diseases. Unfortunately, no cultivar has been bred so far and selections of superior individuals meeting the requirements are now underway from field and hybrid progenies. So we strengthened research on ecophysiological characteristics growing development of Bletilla. By using a Li-6400XT portable photosynthesis system, this paper studied the ecophysiological characteristics of photosynthesis-transpiration coupling of Bletilla striata during daily variation. The results showed that: (1) The diurnal change in photosynthetic active radiation (PAR) and leaf temperature (Tl) are similar to each other, peaking around midday; (2) Stomatal conductance (Gs), net photosynthetic rate (Pn) and transpiration rate (Tr) presented a bimodal pattern; (3) Pn shows significant positive linear correlation with Tr (the slopes are 2.38 and 3.78, with correlation coefficients of 0.883^{* *} and 0.954^{* *} for sunny and cloudy days, respectively) and presented a good linear coupling with photosynthesis-transpiration of Bletilla striata during daily variation; (4) The regression lines of PAR-Pn and PAR-Tr, Tl-Pn and Tl-Tr, and Gs-Pn and Gs-Tr are similar to each other,while no significant correlation was observed between Pn and Tl; (5) Both Pn and Tr showed a positive dependence on PAR, Tl and Gs, with Gs being the main factor affecting Pn and Tr. Bletilla striata is a type of shade perennial plant able to flourish in conditions of low light intensity. The response of the physiological and biochemical indexes in Bletilla striata seedling leaves was compared under simulated drought stress using different concentrations (0, 5, 20, 40, 60g/L) of PEG 6000 solution. The result showed that chlorophyll content takes on a negative correlation (R²=0.7854) with the increasing PEG concentration, and relative conductivity takes on a positive correlation (R²=0.8755) with the increasing PEG concentration. Under osmotic stress, using different concentrations of PEG 6000 solution, the relative water content of Bletilla striata showed a lower rate of reduction.