茶树蒸腾特性的研究

茶树蒸腾速率和气孔导度因品种、叶位不同而异．抗旱性强的品种具有低的气孔导度;鱼叶的蒸腾速率和气孔导度接近或高于真叶．茶树叶片蒸腾速率夏、秋季最高,春季次之,冬季最低．在晴天,茶树蒸腾速率和气孔导度的日变化呈单峰型,以中午前后最高;其日变化与光量子通量密度、叶温、蒸汽压亏缺等因子显著相关;光量子通量密度对蒸腾速率和气孔导度影响较明显．     

Cell water potential,osmotic potential,and turgor in the epidermis and mesophyll of transpiring leaves

Water potential, osmotic potential and turgor measurements obtained by using a cell pressure probe together with a nanoliter osmometer were compared with measurements obtained with an isopiestic psychrometer. Both types of measurements were conducted in the mature region of Tradescantia virginiana L. leaves under non-transpiring conditions in the dark, and gave similar values of all potentials. This finding indicates that the pressure probe and the osmometer provide accurate measurements of turgor, osmotic potentials and water potentials. Because the pressure probe does not require long equilibration times and can measure turgor of single cells in intact plants, the pressure probe together with the osmometer was used to determine in-situ cell water potentials, osmotic potentials and turgor of epidermal and mesophyll cells of transpiring leaves as functions of stomatal aperture and xylem water potential. When the xylem water potential was-0.1 MPa, the stomatal aperture was at its maximum, but turgor of both epidermal and mesophyll cells was relatively low. As the xylem water potential decreased, the stomatal aperture became gradually smaller, whereas turgor of both epidermal and mesophyll cells first increased and afterward decreased. Water potentials of the mesophyll cells were always lower than those of the epidermal cells. These findings indicate that evaporation of water is mainly occurring from mesophyll cells and that peristomatal transpiration could be less important than it has been proposed previously, although peristomatal transpiration may be directly related to regulation of turgor in the guard cells.     

4种针叶幼树光合速率,蒸腾速率与土壤含水量的关系及其抗旱性研究

对半干旱区４种针叶幼树的光合速率、蒸腾速率与土壤含水量关系的分析表明,二者均有随土壤含水量下降而减小的趋势,其关系可用回归方程ｙ＝Ａ＋Ｂｅ（－ｋｘ）表示．依此式计算出的净光合速率（Ｙ）等于零时的土壤含水量（Ｘ）值,各树种间有明显的差别,该值小的树种具有较强的抗旱性．其抗旱性顺序为侧柏＞樟子松＞油松＞白扦．     

矮嵩草草甸主要植物气孔分布及开闭规律与蒸腾强度的关系

本文研究了高寒矮嵩草草甸6种植物叶片气孔的分布、密度和开闭日变化规律与蒸腾强度的关系。结果表明：多数植物上下表皮均有气孔分布,而矮嵩草的气孔集中分布在下表皮,羊茅的气孔集中分布在上表皮。同一植物类群中,叶片气孔密度大者,植物蒸腾强度也相对较高。气孔日变化是在日出后,随气温和大气湿度的变化而变化,在9时和午后3时气孔几乎全部张开,然后逐渐关闭。植物蒸腾强度随气孔开闭而发生变化,矮嵩草的蒸腾强度在11时左右达到峰值;垂穗披碱草和美丽风毛菊是在午后1时达到峰值,植物没有“午睡” 现象。     

华南地区常见树种导管特征与树干液流的关系

为探讨树木结构与功能的关系,对华南地区常见8种树木边材的导管特征进行观察,并利用Granier热扩散探针法测量干、湿季树干的液流密度,分析导管特征与树干液流的关系。结果表明,除红锥(Castanopsis hystrix)有两种导管外,大叶相思(Acacia auriculaeformis)、荷木(Schima superba)、火力楠(Michelia macclurei)、藜蒴(C.fissa)、马占相思(A.mangium)、柠檬桉(Eucalyptus citriodora)、尾巨桉(E.urophylla×E.grandis)的导管类型单一。导管特征在种间存在明显差异,且导管长度、密度和孔径之间存在明显相关性,它们与标准化的边材面积呈现显著相关。湿季液流最大值与导管特征无明显相关性,但整树最大蒸腾速率与导管特征呈显著相关;树木的日蒸腾量与导管特征也有明显相关性。因此,树木的液流速率并不受树干的导管影响;而树干的导管孔径与边材面积间的负相关权衡机制,可以降低树种间由于导管孔径差异引起的树干的水分输送速率的差异性。     

油松不同种源在北京地区水势和蒸腾速率的比较研究

应用压力室技术和稳态气孔仪,测定了在北京地区8年生人工油松林,7个气候生态型13个种源的水势值季节变化和蒸腾速率的日变化及季节变化。结果表明,油松各种源一年中,水势值最低的是严冬季节(-19.75巴)和高温干旱期(-14.81巴)。从不同生态型水势值来看,差异明显。无论在严寒的一月还是在高温干旱的六月,东北型水势值最高,其次是西北型,南部型最低。西南型略高于南部型。水势值高低还明显表现与越冬死亡率高低的关系,南部型种源水势值最低,越冬死亡率也最高。各种源蒸腾速率日变化和季节变化有明显的规律,与环境因子(光照、气温、大气湿度) 密切相关。在日变化中呈现早、晚低,中午高的“凸形峰曲线”。随着春季温度升高,在季节变化中,五月份升至第一高峰,而六月高温干旱期,蒸腾速率明显下降,形成一个低谷。雨季以后的8、9月份升至全年最高值,11月秋末冬初又下降至很低。全年呈现一双峰曲线。从各生态型种源蒸腾速率来看,差异是很明显的,以东北型最高,其次是西北型,中部型,中西型居中,西南型,南部型最小。除上述外,从针叶形态解剖特征上来看,各生态型也差别明显,东北型、西北型的针叶短、窄、薄,表皮和皮下组织则较厚,而南部型种源的针叶长、宽、厚,表皮及皮下组织则较薄。这均反映了不同生态型避旱机制的差异。     

Differential response of leaf gas exchange to enhanced ultraviolet-B (UV-B) radiation in three species of herbaceous climbingplants

We measured diurnal changes in photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency in three species of herbaceous climbing plants (Luffa cylindrica, Trichosanthes kirilowii and Dioscorea opposita) exposed to two intensities of UV-B radiation: 3.0 μw cm^?2 (R1) and 8.0 μw cm^?2 UV-B (R2) radiation under ambient growth conditions. Responses differed per species and per treatment. In Luffa all values increased compared to the Control in both treatments, except for stomatal conductance in R2. In Trichosanthes photosynthetic rates and water use efficiency increased, while the transpiration rates decreased under both treatments, and stomatal conductance was lower in R1. In Dioscorea photosynthetic rates and water use efficiency decreased under both treatments, while the transpiration rates and stomatal conductance increased. The results suggested that to some extent increased UV-B radiation was beneficial to the growth of L. cylindrica and T. kirilowii, but detrimental to D. opposita.     

Underground water use by Eucalyptus trees in an arid climate

 Expanding the area of tree plantations in the Negev desert of Israel requires prior quantification of the water resources in small watersheds. Combined hydrological and physiological measurements were used to study a “liman” (floodwater irrigated plot) in the Negev highlands, where Eucalyptus and other tree species are grown successfully. The amount of water flowing into the liman, surplus water flowing out of the liman, temporal soil moisture distribution, and water uptake by the trees were determined. Depending on rainfall intensity and distribution during the season, the liman received 2 – 3 times the total seasonal rainfall. Although the study was conducted during a year with a negligible amount of rainfall, the transpiration rate was closely correlated with potential transpiration throughout the year. The amount of water extracted from the soil was less than the time-integrated transpiration rate from the trees, suggesting that a water source other than soil water storage was available to the trees. We suggest that the trees extracted water from the rock fractures and/or utilized the lateral flows over the rock/soil interface.     

刺槐林水分生态研究

 本文以定位观测资料为基础,对晋西北黄土丘陵沟壑区人工刺槐林的水分生态特点进行了研究。结果表明,在年生长期中,刺槐林地水分条件严酷、土壤有效水分少。生长期刺槐的蒸腾强度为0.1140g·g-1·h-1±0.0586(平均值±标准差);蒸腾强度日变化与光照强度日变化的关系最为明显;与气温日变化的关系次之;但与相对湿度日变化的关系则不明显。生长期刺槐的水势为1.759-Mpa±0.457(平均值±标准差)。水势的日变化与气温日变化的关系最为明显,与相对湿度日变化的关系次之;而与光照强度日变化的关系最不明显。刺槐的蒸腾强度季节变化与土壤水分含量季节变化的关系不够显著;水势的季节变化与土壤水分含量季节变化的关系显著;但它们的季节变化与光照强度、气温和相对湿度季节变化的关系均不够显著。刺槐的蒸腾耗水量,林分总蒸散量分别占同期降水量的16.3%和68.0%,     

Genetic analysis of carbon isotope discrimination and agronomic characters in a bread wheat cross

Carbon isotope discrimination () has been suggested as a selection criterion to improve transpiration efficiency (W) in bread wheat (Triticum aestivum L.). Cultivars Chinese Spring with low A (high W) and Yecora Rojo with high (low W) were crossed to develop F₁, F₂, BC₁, and BC₂ populations for genetic analysis of and other agronomic characters under well-watered (wet) and water-stressed (dry) field conditions. Significant variation was observed among the generations for only under the wet environment. Generation x irrigation interactions were not significant for . Generation means analysis indicated that additive gene action is of primary importance in the expression of under nonstress conditions. Dominance gene action was also detected for , and the direction of dominance was toward higher values of . The broad-sense and the narrow-sense heritabilities for were 61 % and 57% under the wet conditions, but were 48% and 12% under the draughted conditions, respectively. The narrow-sense heritabilities for grain yield, above-ground dry matter, and harvest index were 36%, 39%, and 60% under the wet conditions and 21%, 44%, and 20% under dry conditions, respectively. The significant additive genetic variation and moderate estimate of the narrow-sense heritability observed for indicated that selection under wet environments should be effective in changing in spring bread wheat.