徐州石灰岩山地4种乔木树种光合特性比较

为比较困难山地4种乔木树种光合特性的差异,在自然条件下,利用Li-6400便携式光合仪测定枫香、黄栌、栾树和梧桐的光合参数.结果表明:黄栌的净光合速率日变化呈双峰曲线,其他3种乔木净光合速率日变化呈单峰曲线;4种乔木都有午休现象,它们的日均净光合速率和蒸腾速率由大到小依次为:栾树＞枫香＞黄栌＞梧桐;4种乔木午后气孔导度值都有所降低,且梧桐的日均气孔导度最小;枫香和栾树日均水分利用率最高,黄栌和梧桐的水分利用率较低.4种乔木中,栾树的光合能力最强,梧桐的日均蒸腾速率和气孔导度是4种乔木中最小的,最为耐旱.影响4种乔木光合作用的主要因子是气孔导度和空气相对湿度.     

水分胁迫下新西伯利亚银白杨光合能力变化

采用室内盆栽试验,研究不同程度水分胁迫24 d对新西伯利亚银白杨叶片光合生产力和渗透调节物质含量的影响.结果表明：水分胁迫抑制了新西伯利亚银白杨幼苗叶片的光合能力,提高了叶片细胞中可溶性蛋白质含量,并影响了叶片中可溶性糖含量.随着胁迫强度和胁迫时间的增加,叶片净光合速率、蒸腾速率和气孔导度均显著减小.叶片净光合速率与蒸腾速率和气孔导度呈极显著正相关关系,与土壤含水量呈显著正相关关系.气孔导度蒸与腾速率呈极显著正相关关系,与土壤含水量、可溶性糖含量呈显著正相关关系.蒸腾速率与可溶性糖含量呈显著正相关关系.在土壤相对含水量≥25％的条件下,净光合速率下降主要由气孔因素导致.在土壤相对含水量＜25％的条件下,净光合速率下降主要由非气孔限制导致.     

南召宝天曼生境下山茱萸光合生理生态特性研究

在完全自然生长不离体的情况下,利用Li-6400测定南召宝天曼生境下山茱萸7月份的光合生理生态指标.结果表明;山茱萸净光合速率日变化呈双峰曲线,具有光合"午休"现象且由非气孔限制因素所致;山茱萸净光合速率与叶片气孔导度、胞间C02浓度、气孔限制值呈线性相关,与光合有效辐射呈二次抛物线型相关,与其它生理生态因子之间没有直接的显著相关,但逐步回归多元统计分析显示利用叶片气孔导度和叶片温度二因子预测山茱萸净光合速率精度较高;在叶温28C和空气CO2浓度360μmol·tool-1条件下,山茱萸净光合速率随光合有效辐射的增强而提高,光补偿点和光饱和点分别为25 μmol·m-2·s-1、1000μmol·m-2·s1,在此条件下,净光合速率与蒸腾速率和叶片气孔导度没有显著的相关关系．但与胞间CO2浓度呈二次抛物线璎显著相关;在叶温28C和光合有效辐射900 μmol·m-2·s-1条件下,净光合速率随着CO2浓度的增加而提高,CO2补偿点和CO2饱和点分别为100μmol·mol-1、1400μmol·mol-1此条件下净光合速率与蒸腾速率和胞间CO2浓度均星对数曲线显著正相关.     

‘欧美杨177’幼苗光合指标日变化分析

文章利用Li-6400XT测定了欧美杨177幼苗净光合速率,研究其日变化与环境因子的关系。结果表明:欧美杨177净光合速率、蒸腾速率和气孔导度日变化均呈现"双峰"曲线,表现出明显的光合"午休"现象,中午净光合速率降低主要受气孔限制因素限制;净光合速率峰值出现在10:00时和14:00时,分别为27.55μmol·m~(-2)·s~(-1)和24.85μmol·m-2·s-1。14:00～18:00时段,胞间CO2浓度升高,气孔限制值减小,净光合速率下降主要受非气孔因素限制;欧美杨177净光合速率与气孔导度、光合有效辐射呈极显著正相关(r=0.973**、r=0.976**),与胞间CO2浓度呈极显著负相关(r=-0.918**),对蒸腾速率影响最大的是空气CO_2浓度。     

南天竹光合日变化规律与环境因子的相关性

为了了解南天竹光合作用日变化规律与环境因子之间的相关性,为南天竹的资源利用、栽培、保育工作提供试验依据,采用Li-6400便携式光合作用测定仪测定了南天竹净光合速率、蒸腾速率、气孔导度的日变化以及光合有效辐射、空气相对湿度、胞间CO2浓度等环境因子的日变化。结果表明:自然光照条件下,南天竹净光合速率与光合有效辐射、蒸腾速率呈正相关,相关系数分别为0.849、0.869,与胞间CO2浓度呈负相关,相关系数为-0.879,与气孔导度、相对湿度的相关性不显著;蒸腾速率与气孔导度也呈显著正相关,相关系数为0.904;胞间CO2浓度与光合有效辐射也呈负相关,相关系数为-0.896。     

石灰岩山地坡位对侧柏光合蒸腾特性的影响

为分析困难山地不同坡位侧柏光合和蒸腾作用等生理特性的差异,利用Li-6400便携式光合仪对石灰岩山地4种坡位侧柏的净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、光合有效辐射(rPAR)、空气相对湿度(Hr)、气温(Ta)等指标进行测定.结果表明:不同坡位侧柏净光合速率最大值均出现在8:00,底坡和中坡侧柏在中午都出现午休现象;坡位越高,侧柏日均净光合速率越低.各样地侧柏蒸腾速率日变化均呈双峰曲线,日均蒸腾速率由大到小依次为顶坡＞平地＞中坡＞底坡.底坡侧柏气孔导度在中午时值最小,且日均水分利用效率最高.相关性分析表明,研究区侧柏光合蒸腾作用的主要影响因子是气孔导度、光合有效辐射和空气相对湿度,底坡是最适合侧柏生长的位置.     

NaHCO3胁迫下新西伯利亚银白杨幼苗生长和光合能力变化

采用室内盆栽试验,研究不同浓度NaHCO3溶液胁迫24天对新西伯利亚银白杨幼苗的生长状况和叶片光合生产力的影响。结果表明:NaHCO3胁迫抑制新西伯利亚银白杨幼苗的生长和叶片的光合能力。苗木高度、地径和总生物量的增量、叶片净光合速率、蒸腾速率和气孔导度均随着胁迫强度的增加和胁迫时间的延长而显著减小,其中苗木地下生物量增量的降幅大于地上部分。叶片净光合速率与蒸腾速率呈极显著正相关关系,与气孔导度呈显著正相关关系,与胁迫强度呈显著负相关关系。影响新西伯利亚银白杨叶片光合特性的因素有气孔限制和非气孔限制2方面。NaHCO3溶液浓度小于等于48mmol·L-1时,叶片净光合速率下降主要受气孔限制;NaHCO3溶液浓度大于48mmol·L-1时,叶片净光合速率下降主要由非气孔因素限制。     

3个杨树品种在鲁西地区光合生理特性研究

在鲁西地区对鲁林2号、鲁林3号、2025杨(对照)3个杨树品种的净光合速率、蒸腾速率、气孔导度等生理指标进行测定的结果表明:鲁林2号、鲁林3号的净光合速率显著高于对照,具有高产潜能。相关性分析发现,蒸腾速率、空气温度与杨树净光合速率分别呈极显著和显著正相关关系,说明杨树要实现高产,必须有充分的水、热条件做保障。     

不同核桃品种光合特性比较研究

用Li-6400便携式光合作用测定系统,对香玲、鲁光、清香、西林3号、西洛3号5个核桃品种的光合生理特性进行了研究。结果表明,5个品种的净光合速率日平均值大小顺序为香玲>鲁光>清香>西林三号>西洛3号。净光合速率日变化、蒸腾速率日变化和气孔导度日变化曲线均呈单峰型和双峰型;不同品种净光合速率与蒸腾速率、气孔导度,蒸腾速率与气孔导度均呈极显著正相关(P<0.01);香玲品种核桃苗叶光补偿点、光饱和点分别为58.997、1 450μmo1·m-2·s-1。     

紫荆叶片夏季水分利用效率的日变化

紫荆叶片净光合速率日进程曲线为“双峰”形，光合效率午间明显降低，主要由非气孔限制引起。蒸腾速率和气孔导度的日变化为“单峰”形，午间最高。水分利用效率早晚较高、午间较低。净光合速率、蒸腾速率、气孔导度和水分利用效率与一些环境因子的相关性都达到0．01显著水平。利用多元逐步回归方法分别得到了净光合速率、蒸腾速率、气孔导度和水分利用效率与环境因子的最优方程。     

Seasonal air and soil temperature effects on photosynthesis in red spruce (Picea rubens) saplings

Net photosynthesis and stomatal conductance were measured in ten red spruce (Picea rubens Sarg.) saplings, growing near Ithaca, New York, throughout the early spring and late-fall growing periods. Gas exchange and daily minimum and maximum soil and air temperatures were also measured. Linear regression analysis showed that rates of net photosynthesis were positively correlated with both minimum daily soil and air temperatures but that minimum soil temperature was a better predictor of net photosynthesis. Moreover, net photosynthesis was more sensitive to changes in soil temperature than to changes in air temperature, and photosynthesis was approximately twice as sensitive to temperature changes during the fall than during the spring.     

Influence of climate and fertilization on net photosynthesis of mature slash pine

Net photosynthesis was measured under field conditions in 23-year-old slash pine (Pinus elliottii Engelm. var. elliottii) trees to determine how it was affected by fertilization and climate. There was only a small decrease in rates of net photosynthesis from late summer through winter demonstrating that appreciable carbon gain occurs throughout the year in slash pine. Although fertilization substantially increased leaf area and aboveground biomass, it only slightly increased the rate of net photosynthesis. Simultaneous measurements of gas exchange in fertilized and unfertilized (control) plots allowed the detection of a small, but statistically significant difference in average net photosynthesis of 0.14 micro mol m(-2) s(-1). Irradiance, and to a lesser extent air temperature, were the environmental factors that exerted the most control on net photosynthesis. The highest rates of net photosynthesis occurred between air temperatures of 25 and 35 degrees C. Because air temperatures were within this range for 46% of all daylight hours during the year, air temperature was not often a significant limitation. Soil and atmospheric water deficits had less effect on photosynthesis than irradiance or air temperature. Although the depth to the water table changed during the year from 10 to 160 cm, predawn and midday xylem pressure potentials only changed slightly throughout the year. Predawn values ranged from -0.63 to -0.88 MPa in the control plot and from -0.51 to -0.87 MPa in the fertilized plot and were not correlated with water table depth. There was no correlation between xylem pressure potentials and net photosynthesis, presumably because water uptake was adequate. Although vapor pressure deficits reached 3.5 kPa during the summer, they had little effect on net photosynthesis. Over a vapor pressure deficit range from 1.0 to 3.0 kPa, net photosynthesis only decreased 21%. No differences in responses to these environmental factors could be attributed to fertilization.     

Photosynthesis and water relations of the floodplain tree, boxelder (Acer negundo L.)

During summer, gas exchange and water relations were measured in mature boxelder (Acer negundo L.) trees growing on a floodplain in central Indiana, USA. A shallow (< 1.25-m deep) water table and repeated flooding kept the soil water potential above -0.5 MPa at all times. Net photosynthesis and stomatal conductance were influenced primarily by light and, to a lesser extent, by leaf temperature, but showed no relationships with leaf-to-air water vapor gradient or leaf water potential. Throughout the summer, there was no midday stomatal closure on any measurement day, and leaf water potential at dawn and minimum daily leaf water potential remained above -0.4 and -1.4 MPa, respectively. Nevertheless, there was a seasonal decline in leaf osmotic potentials at saturation and turgor-loss point. Seasonal changes in maximum daily net photosynthesis and stomatal conductance, minimum daily leaf water potential and soil-to-leaf hydraulic conductance were not related to seasonal changes in soil water potential, air or soil temperature, or water table depth. Seasonal responses of net photosynthesis to intercellular CO(2) indicated that net photosynthesis was controlled primarily by nonstomatal factors. High soil water and a shallow water table may have kept soil-to-leaf hydraulic conductance large (5-9 mmol m(-1) s(-1) MPa(-1)) throughout the summer, permitting the trees to keep their stomata open, yet maintain leaf turgor and high net photosynthesis during the hot, low-humidity afternoons. This could also account for the dominance of nonstomatal influences on net photosynthesis.     

Winter photosynthesis of red spruce from three Vermont seed sources

We evaluated winter (January through March) carbon assimilation of red spruce (Picea rubens Sarg.) from three Vermont seed sources grown in a common garden in northwestern Vermont. Although CO(2) exchange rates were generally low, net photosynthetic rates increased during two prolonged thaws. Significant correlations between CO(2) exchange rates and multiday air temperature means supported our observations of enhanced gas exchange during extended periods of elevated temperature. Increases in photosynthesis during thaws occurred before observed increases in leaf conductance, indicating that initial changes in photosynthesis were probably not associated with changes in stomatal aperture. Results of correlations between photosynthetic rates and PAR suggested that solar irradiance did not have a strong effect on winter carbon capture. Rates of net photosynthesis differed among seed sources. Trees from the Mt. Mansfield source had the highest average rates of photosynthesis and, at times, rates for individual trees from this source approximated those occurring during the growing season. Because seed sources differed in photosynthetic rates but not in leaf conductance, we conclude that differences in winter photosynthesis among seed sources were primarily attributable to factors other than changes in stomatal aperture.     

Midday depression of net photosynthesis in the tropical rainforest tree Eperua grandiflora: contributions of stomatal and internal conductances,respiration and Rubisco functioning

High midday temperatures can depress net photosynthesis. We investigated possible mechanisms underlying this phenomenon in leaves of Eperua grandiflora (Aubl.) Benth. saplings. This tropical tree establishes in small gaps in the rainforest canopy where direct sunlight can raise midday temperatures markedly. We simulated this microclimate in a growth chamber by varying air temperature between 28 and 38 degrees C at constant vapor pressure. A decrease in stomatal conductance in response to an increase in leaf-to-air vapor pressure difference (deltaW) caused by an increase in leaf temperature (Tleaf) was the principal reason for the decrease in net photosynthesis between 28 and 33 degrees C. Net photosynthesis decreased further between 33 and 38 degrees C. Direct effects on mesophyll functioning and indirect effects through deltaW were of similar magnitude in this temperature range. Mitochondrial respiration during photosynthesis was insensitive to Tleaf over the investigated temperature range; it thus did not contribute to midday depression of net photosynthesis. Internal conductance for CO2 diffusion in the leaf, estimated by combined gas exchange and chlorophyll fluorescence measurements, decreased slightly with increasing Tleaf. However, the decrease in photosynthetic rate with increasing Tleaf was larger and thus the difference in CO2 partial pressure between the substomatal cavity and chloroplast was smaller, leading to the conclusion that this factor was not causally involved in midday depression. Carboxylation capacity inferred from the CO2 response of photosynthesis increased between 28 and 33 degrees C, but remained unchanged between 33 and 38 degrees C. Increased oxygenation of ribulose-1,5-bisphosphate relative to its carboxylation and the concomitant increase in photorespiration with increasing Tleaf were thus not compensated by an increase in carboxylation capacity over the higher temperature range. This was the principal reason for the negative effect of high midday temperatures on mesophyll functioning.     

升高气温对旱柳光合和生长的影响

工业革命以来 ,大气ＣＯ2 含量增加了 30 % ,预计到 2 1世纪中叶大气ＣＯ2 含量将增加 1倍。与此同时 ,ＣＨ4、Ｎ2 Ｏ、ＣＦＣｓ等温室气体的排放也不断增加 (Ｖｉｔｏｕｓｅｋ ,1 994)。这些温室气体含量的增加必将导致全球性气候变化 (Ｖｉｔｏｕｓｅｋ ,1 994;Ｍｃｌｅｏｄｅｔａｌ.,1 999)。根据大气环流模型 (ｇｅｎｅｒａｌｃｉｒｃｕｌａｔｉｏｎｍｏｄｅｌｓ,ＧＣＭｓ)的预测 ,2 1世纪全球气温将可能平均升高 1 5～ 4 5℃ (Ｈｏｕｇｈｔｏｎｅｔａｌ.,1 996)。在 1 95 1～ 1 989年的约 40ａ间 ,中国半干旱区的平均气温升高了 0 5…     

Photosynthetic Characteristics of Ash and Larch in Mixture and Pure stands

IntroductionDuringthepasttwodecades,studieshaverevealedthatgrowingash(Fnainusmandshurica)andlarch(LarlksPP.)togetherinaproperwaycanincreasetheproduc-tivityQfthestandsI"'}'-'].Theyieldimprovementmechanismsattributetotwoaspects,i.e.,theabovegroundandundergr…     

Higher growth temperatures decreased net carbon assimilation and biomass accumulation of northern red oak seedlings near the southern limit of the species range

If an increase in temperature will limit the growth of a species, it will be in the warmest portion of the species distribution. Therefore, in this study we examined the effects of elevated temperature on net carbon assimilation and biomass production of northern red oak (Quercus rubra L.) seedlings grown near the southern limit of the species distribution. Seedlings were grown in chambers in elevated CO(2) (700 μmol mol(-1)) at three temperature conditions, ambient (tracking diurnal and seasonal variation in outdoor temperature), ambient +3 °C and ambient +6 °C, which produced mean growing season temperatures of 23, 26 and 29 °C, respectively. A group of seedlings was also grown in ambient [CO(2)] and ambient temperature as a check of the growth response to elevated [CO(2)]. Net photosynthesis and leaf respiration, photosynthetic capacity (V(cmax), J(max) and triose phosphate utilization (TPU)) and chlorophyll fluorescence, as well as seedling height, diameter and biomass, were measured during one growing season. Higher growth temperatures reduced net photosynthesis, increased respiration and reduced height, diameter and biomass production. Maximum net photosynthesis at saturating [CO(2)] and maximum rate of electron transport (J(max)) were lowest throughout the growing season in seedlings grown in the highest temperature regime. These parameters were also lower in June, but not in July or September, in seedlings grown at +3 °C above ambient, compared with those grown in ambient temperature, indicating no impairment of photosynthetic capacity with a moderate increase in air temperature. An unusual and potentially important observation was that foliar respiration did not acclimate to growth temperature, resulting in substantially higher leaf respiration at the higher growth temperatures. Lower net carbon assimilation was correlated with lower growth at higher temperatures. Total biomass at the end of the growing season decreased in direct proportion to the increase in growth temperature, declining by 6% per 1 °C increase in mean growing season temperature. Our observations suggest that increases in air temperature above current ambient conditions will be detrimental to Q. rubra seedlings growing near the southern limit of the species range.     

Diurnal patterns of leaf photosynthesis, conductance and water potential at the top of a lowland rain forest canopy in Cameroon: measurements from the Radeau des Cimes

Diurnal patterns of leaf conductance, net photosynthesis and water potential of five tree species were measured at the top of the canopy in a tropical lowland rain forest in southwestern Cameroon. Access to the 40 m canopy was by a large canopy-supported raft, the Radeau des Cimes. The measurements were made under ambient conditions, but the raft altered the local energy balance at times, resulting in elevated leaf temperatures. Leaf water potential was equal to or greater than the gravitational potential at 40 m in the early morning, falling to values as low as -3.0 MPa near midday. Net photosynthesis and conductance were typically highest during midmorning, with values of about 10-12 micro mol CO(2) m(-2) s(-1) and 0.2-0.3 mol H(2)O m(-2) s(-1), respectively. Leaf conductance and net photosynthesis commonly declined through midday with occasional recovery late in the day. Photosynthesis was negatively related to leaf temperature above midday air temperature maxima. These patterns were similar to those observed in other seasonally droughted evergreen communities, such as Mediterranean-climate shrubs, and indicate that environmental factors may cause stomatal closure and limit photosynthesis in tropical rain forests during the midday period.     

土壤干旱胁迫及复水对紫叶矮樱光合特性的影响

以盆栽3年生紫叶矮樱为试材,采用称重控水法,研究土壤干旱胁迫及复水对紫叶矮樱光合特性的影响。结果表明：干旱条件下,随着胁迫程度的加重,紫叶矮樱的叶水势、净光合速率、蒸腾速率、气孔导度和胞间CO2浓度下降,叶绿素、花青苷含量和水分利用效率先升高再降低;复水后,叶水势、净光合速率、蒸腾速率、叶绿素含量、花青苷含量和水分利用效率升高,表明紫叶矮樱具有胁迫后补偿生长特征。