Midday Depression Research Articles

Effects of tillage practices on photosynthetic performance diurnal variation during filling stage and grain yield of winter wheat

Photosynthesis characteristics of winter wheat under different tillage practices during fil-ling stage are vital for dry matter accumulation, transfer, and yield development. A field experiment, including no-till with residue removal (NT), no-till with residue retention (NTS), rotary tillage with residue removal (RT), rotary tillage with residue retained (RTS), subsoiling with residue removal (DT), subsoiling with residue retained (DTS), plow tillage with residue removal (CT), and plow tillage with residue retained (CTS) was conducted at Wuqiao experimental station of China Agricultural University since October 2008. The diurnal variation of photosynthetic characteristics of flag leaf, photosynthetic response curve, and crop yield under different tillage practices were evaluated during winter wheat filing stage in this study. The results showed thatthe net photosynthetic rate and stomatal conductance of flag leaf both diurnally varied with the bimodal curve, and the net photosynthetic rates were higher under treatments with residue retained than those under with residue removal. Diurnal variation of intercellular carbon dioxide concentration was observed with a "V-shaped wide mouth" bimodal curve under all treatments. Daily transpiration rate exhibited "double peak curve", except for the "single peak curve" under DTS, RTS and RT. The stimulated net photosynthetic rate was increased by 20.0%, 21.7%, 19.7%, 21.5%, 0.8%, 12.1% and 4.2% under NT, DT, RT, CT, CTS, RTS, and CTS, compared with DTS, respectively. Photosynthetic response curves were fitted better under treatments with residue retained than under treatments with residue removal. As for crop grain yields, the highest one was observed under DTS, following by RTS and CTS, and the lowest under CT. Crop grain yield was increased by 10.8%, 1.3%, 2.1%, 5.4%, 11.9%, 12.4%, and 12.6% under DTS, compared with NTS, RTS, CTS, NT, DT, RT, and CT, respectively. Thus, residue retaining under different tillage practices (e.g. NTS and DTS) could mitigate the mid-day depression of photosynthesis, maintain a high photosynthetic rate of winter wheat, and improve the dry matter accumulation and crop production.

Effects of exogenous nitric oxide on the photosynthetic characteristics of bamboo (Indocalamus barbatus McClure) seedlings under acid rain stress

The effects of the exogenous application of nitric oxide (NO, in the form of sodium nitroprusside, SNP) on the diurnal variation in photosynthesis, chlorophyll content, chlorophyll fluorescence, light response curve and the net assimilation of CO2 against intercellular CO2 concentration (A-Ci) curve parameters were investigated in the leaves of bamboo (Indocalamus barbatus McClure) exposed to simulated acid rain (SAR, pH 3.0) stress. According to the results of the diurnal variation in photosynthesis, foliar applications of 100–400 mg/L SNP effectively inhibited the decrease in net photosynthetic rate (Pn) as a result of non-stomatal factors, and mitigated midday depression under acid rain stress. The mitigating effect was most pronounced at 400 mg/L SNP. However, at higher concentrations of SNP (700 and 1000 mg/L), the mitigating effect became weak and even counterproductive. The results of the chlorophyll content, light response and A-Ci curve parameters suggested that the regulating role of NO against acid rain in the photosynthetic processes occurs through improving not only the efficiency of the light-harvesting and the activity of photosynthetic apparatus, but also the absorption of CO2 and the availability of CO2 for photosynthesis. The results of the chlorophyll fluorescence investigation further indicated that NO protected PSII activity from the damage of acid rain toxicity by enhancing the electron transport activity and photochemical efficiency, especially concerning the increase in the proportion of PSII open reaction centers. Furthermore, NO induced an increase in photorespiration (Rp), rather than an increase in non-photochemical quenching (NPQ), to dissipate the excessive excitation energy, which provided some protection to the photosynthetic apparatus under acid rain stress.

Correlation research of photosynthetic characteristics and medicinal materials production with 4 Uncariae Cum Uncis

Using four Uncariae Cum Uncis materials including Uncaria sinensis (HGT), U. hirsutea (MGT), Jianhe U. rhynchophylla (JHGT) and U. rhynchophylla(GT) as the research objects, the correlations between medicinal materials' yield and photosynthetic ecophysiology-factors in the plant exuberant growth period were studied. Results showed that the Uncaria plants net photosynthetic rate (Pn) changed by unimodal curve. There was not "midday depression" phenomenon. There was a different relationship among the photosynthetic ecophysiology-factors and between photosynthetic ecophysiology-factors and medicinal materials' yield. Pn,Tl,Gs had a significant correlation with medicinal materials' yield（M）and were the most important factors of growth.

Vertical distribution characteristics of photosynthetic parameters for Phragmites australis in Liaohe River Delta wetland, China

ABSTRACTA field experiment was undertaken to measure diurnal variation in photosynthetic and light-response parameters of leaves of Phragmites australis growing in the Liaohe River Delta wetland, China. Four developmental stages (leaf-expansion, jointing, heading, and mature stages) and three (upper, middle, and lower layers) or five vertical layers (top, upper, middle, lower, and bottom layers) were delimited. Diurnal variations in net photosynthetic rate, stomatal conductance, and transpiration rate showed single-peak or double-peak curves that were lower in the morning and evening and higher at noon. The diurnal variation in intercellular CO2 concentration showed the opposite pattern, with higher values in the morning and evening and lower values at noon. Midday depression was observed under strong light, in the top, upper, and middle layers but not under weak light or in the lower and bottom layers. The net photosynthetic rate, stomatal conductance, and transpiration rate were higher in the upper layer, and gradually decreased in value and in diurnal variability below the middle layer with increasing proximity to the plant base. Leaves showed a strong photosynthetic ability at the leaf-expansion stage, with the maximum net photosynthetic rate in the middle layer and the minimum net photosynthetic rate in the lower layer. Photosynthetic ability increased at the jointing and heading stages. The maximum net photosynthetic rate was in the upper or middle layers and the minimum in the bottom layer. Photosynthetic ability was weak at the mature stage. The light compensation point in leaves was 27.1–38.2, 24.6–29.5, 27.7–72.6, and 15.4–31.0 μmol⋅m−2⋅s−1 at the leaf-expansion, jointing, heading, and mature stages, respectively. The developmental stages of P. australis leaves were ranked, from highest ability to use weak light to lowest, as follows: mature stage > jointing stage > leaf-expansion stage > heading stage.

不同强度净风频繁吹袭对樟子松(Pinus sylvestris var.mongolica)幼苗光合蒸腾特征的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同强度净风频繁吹袭对樟子松(Pinus sylvestris var.mongolica)幼苗光合蒸腾特征的影响 DOI: 10.5846/stxb201510142070 作者: 作者单位: 中国科学院寒区旱区环境与工程研究所,中国科学院寒区旱区环境与工程研究所,鲁东大学生命科学学院,中国科学院寒区旱区环境与工程研究所,中国科学院寒区旱区环境与工程研究所,中国科学院寒区旱区环境与工程研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（31270752，30972422） Effects of wind frequency on the rates of photosynthesis and transpiration in Pinus sylvestris var. mongolica seedlings Author: Affiliation: Cold and Arid Regions Environment and Engineering Institute,CAS,Lanzhou,Cold and Arid Regions Environment and Engineering Institute,CAS,Lanzhou,,Cold and Arid Regions Environment and Engineering Institute,CAS,Lanzhou,Cold and Arid Regions Environment and Engineering Institute,CAS,Lanzhou,Cold and Arid Regions Environment and Engineering Institute,CAS,Lanzhou Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了解不同强度净风频繁吹袭对樟子松幼苗光合蒸腾特性的影响，2013年春季在内蒙古科尔沁沙地研究了0（对照）、6、9、12、15、18 m/s等6个风速处理（分别相当于0、4、5、6、7、8级风）4次吹袭下樟子松幼苗光合速率、蒸腾速率、水分利用效率等指标的变化。结果表明，净风频繁吹袭没有改变樟子松幼苗的光合速率和蒸腾速率的日变化规律，但可使其光合蒸腾的“午休”时间加长、“休眠”程度加深；随着风吹强度的增加，其日均光合能力和蒸腾速率显著降低，其中18 m/s处理较对照分别下降27.6%和22.3%；随着风吹强度增加，气孔导度、胞间CO2浓度均先下降后回升，除18 m/s处理胞间CO2浓度显著高于CK外，其他处理均显著低于CK；随着风吹强度增加，水分利用效率和光能利用效率均先增加后下降，其中除18 m/s处理的水分利用效率显著低于CK，6 m/s处理的光能利用效率高于CK外，其他处理的水分利用效率均高于CK，光能利用效率均低于CK；日均光合蒸腾速率的下降主要源于气孔导度的降低，而水分利用效率和光能利用效率的变化均受制于光合速率和蒸腾速率的变化。 Abstract:To understand the effects of frequent gusts of wind on the rates of photosynthesis and transpiration in Pinus sylvestris var. mongolica seedlings, a field wind-blowing experiment using a wind speed gradient of 0 (CK), 6, 9, 12, 15, and 18 m/s and four episodes of wind blowing was conducted in the spring of 2013 in the Horqin Sand Land of Inner Mongolia. The results showed that:1) Frequent wind blowing did not change the diurnal variation in the rates of photosynthesis and transpiration in seedlings, but resulted in in an extension of midday depression and a higher degree of dormancy in photosynthesis and transpiration. 2) Increasing the wind strength led to a significant decrease in the average daily rates of photosynthesis and transpiration, with a decrease of 27.6% and 22.3% in the 18 m/s-treated seedlings compared to the CK, respectively. With an increase in wind strength, stomatal conductance and intercellular CO2 concentrations first increased and then decreased, and were significant lower in all treatment groups as compared with the CK group, with the exception of intercellular CO2 concentration, which was higher in the 18 m/s group. 3) Increasing the wind-sand flow strength led to a significant increase in water-use efficiency, except for a significant decrease in the 18 m/s treatment group as compared with the CK group. In addition, the efficiency of sunlight energy use tended to decrease except for a significant increase in the 6 m/s-treatment group as compared with the CK group. 4) Decreases in the average daily rates of photosynthesis and transpiration resulted from a decrease in stomatal conductance, and changes in water-use efficiency and sunlight energy-use efficiency resulted from changes in the rates of photosynthesis and transpiration. 参考文献 相似文献 引证文献

The altitudinal effects on photosynthesis of Rosa platyacantha from the Tianshan Mountains in Northwestern China

The altitudinal effects on photosynthesis were measured on progenies of three populations of Rosa platyacantha Schrenk from altitudes of 1,170 (L); 1,580 (M); and 1,920 (H) m a. s. l. During the day, net photosynthetic rate (P N) decreased in all populations due to the high air temperature in the summer. The H population showed a significantly lower P N at noon compared to other populations. The midday depression of P N occurred in L and M populations due to stomatal limitations, while P N inhibition was associated with PSII activity decline in the H population. In order to avoid photodamage, the plants of H population triggered active antioxidant defenses with a higher enzyme activity and redox ratio of ascorbate at midday compared to the L and M populations. However, more oxidative injury still occurred in the H plants at noon due to higher lipid peroxidation. Our results indicated that the provenance significantly affected photosynthesis in R. platyacantha from northwestern China.

Research on photosynthetic and eco-physiological characteristics of Epimedium pseudowushannense in different growing age

Epimedium is a widely used medicinal plants. Due to excessive use of wild resources and resource constraints, artificial cultivation is the only way to achieve sustainable use of resources. E. pseudowushannense is intended to achieve the first cultivated species, but plant production technology is not yet fully mature.The diurnal variation of photosynthetic and eco-physiological characteristics of E. pseudowushannense in different growing age was studied by the CI-340 Portable Photosynthesis System under natural conditions. The net photosynthetic rate (Pn), stomatal conductance (C), intercellular CO2 concentration (Ci), photosynthetically active radiation (PAR), relative humidity (RH), air temperature (Ta), apparent mesophyll conductance (ALMC), transpiration rate (E), leaf temperature (Tl), water use efficiency (WUE) and other photosynthetic physiological factors and environmental factors were measured. The obtained data was analyzed by correlation analysis, path analysis and stepwise multiple-regression analysis to explore the relationship between net photosynthetic rate and physiological and ecological factors. The results show that： ①The daily variation of the Pn, E, ALMC, C of E. pseudowushannense in different growing age took on"two peak type", the Pn was with an obvious midday depression phenomenon at noon.②The Pn, ALMC and C of annuals' were significantly higher than biennial or three-year; but the Ci was basically a three-year > biennial> annual.③The correlation analysis, path analysis and stepwise regression analysis showed that ALMC, Ci, Ta might played important role in the Pn and ranked as ALMC>Ci>Ta.

Remote sensing of assimilating branch light use efficiency using the photochemical reflectance index inHaloxylon ammodendronforest

Five healthy Haloxylon ammodendron trees were randomly selected to monitor the photochemical reflectance index (PRI) and its relation to light use efficiency (LUE) in shaded and sunlit assimilating branches. Linear regression was performed where the results revealed that LUE decreased with seasonal courses with vivid midday depression regardless of light variation within canopies. PRI and LUE decoupled in early spring when the foliage was deeply downregulated, with high correlation ( R 2 = 0.8 , p 0.001 ) during most parts of the year. Measured and estimated LUE were highly correlated for the July to September dataset ( R 2 = 0.73 , p 0.001 ) compared to May to June datasets ( R 2 = 0.35 , p 0.001 ). The estimated LUE for young assimilating branches could be obtained with a high RMSE of 0.01, compared to mature branches with an RMSE of 0.003. The measured LUE values were ∼ 20% higher than estimated LUE during the period from May to June, and values were slightly lower at the end of the growing season. This was attributed to differences in the physiological and biochemical mechanisms controlling the seasonal dynamics of PRI. Therefore, PRI is the best estimator of LUE when age-related changes and canopy light partitioning are considered in assimilating organs. Combined use of PRI with pigments could improve the remote evaluation of LUE.

Solute patterns and diurnal variation of photosynthesis and chlorophyll fluorescence in Korean coastal sand dune plants

Four plant species, Elymus mollis Trin., Carex kobomugi Ohwi, Glehnia littoralis F. Schmidt ex Miq., and Vitex rotundifolia L.f., are dominant perennial species in coastal sand dunes of Korea. We examined a physiological adaptation of these species by measurements of diurnal variation in photosynthesis and chlorophyll (Chl) fluorescence and solute patterns in leaves during one season (June), which is favorable for plant growth of all four species. All four species adopted different strategies in order to utilize radiation and to maintain water status under a fluctuating microclimate. Although the lowest water contents among four plant species was found, E. mollis with a high Chl and K+ content showed better photosynthetic performance, with high stomatal conductance (g s), net photosynthetic rate (P N), instantaneous carboxylation efficiency (CE), and water-use efficiency. Midday depression of P N in E. mollis and G. littoralis, without a reduction of gs, was associated with a reduction in CE and maximum photochemical efficiency of PSII, indicating nonstomatal limitation. Photosynthesis depression in both C. kobomugi and V. rotundifolia, with relatively low g s values, could be attributed to both stomatal and nonstomatal limitations. The high storage capacity for inorganic ions in E. molli, C. kobomugi, and G. littoralis may play an efficient role in regulating photosynthesis and maintaining leaf water status through stomatal control, and can also play an important role in osmotic adjustment.

Characteristics and coordination of source-sink relationships in super hybrid rice

AbstractThis paper discusses the characteristics of source and sink for super hybrid rice and how to coordinate its source-sink relationships for high-yielding cultivation. It is known that super hybrid rice possesses a higher net photosynthetic rate than non-hybrid rice because of its higher grain-leaf area ratio, better stornata traits and less midday depression. However, the sink of super hybrid rice remains large due to its large and numerous spikelets. Furthermore, the relocation of assimilates is smooth in super hybrid rice because of its well-developed vascular structure. However, due to the very large sink of super hybrid rice, it is relatively inefficient in supplying of assimilate products to spikelets, in particular to inferior spikelets. Therefore, reducing the discrepancy between source and sink in super hybrid rice is essential for developing high-yielding cultivation. This can only be achieved by planting cultivars adapted for local environments, raising strong seedling, setting up populations with a high photosynthetic efficiency for increasing the supply of source, and improving the field management in filling stages to the duration of supply of photosynthate to grains.

Reducing cranberry heat stress and midday depression with evaporative cooling

A cultural practice for cooling cranberry plants and avoiding yield losses due to overheating is to turn on sprinkler irrigation for a few minutes when a critical temperature threshold is reached. The purpose of this study was to determine: (i) the critical leaf temperature to start irrigation for evaporative cooling in cranberry production, (ii) the combined effects of heat and water stress, and (iii) the beneficial effects of evaporative cooling through irrigation on field microclimate and plant physiology. The optimum temperature range for carbon dioxide (CO2) assimilation was between 25 and 29°C, with photosynthesis (An) declining by 11% at 33°C and by 22% at 37°C due in part to stomatal limitations. The reduction in An was greater under low soil moisture conditions. When applying sprinkler irrigation in the field, leaf temperature was reduced by 5–10°C and the efficiency of evaporative cooling was greater, with greater vapor pressure deficit of the air within the crop canopy before the irrigation. Under controlled environmental conditions, one cooling event resulted in a carbon gain of 19% relative to untreated plants and was able to reduce midday depression. Additional cooling events during the day had no significant effect on carbon gain. Among the main cranberry-growing regions, New Jersey is an area where sprinkler irrigation for evaporative cooling could be beneficial for preventing yield limitations due to heat stress.

Plant water relations and canopy temperature depression for assessing water stress tolerance of potato

An experiment was conducted with five potato genotypes at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur during 2010–2011 under control and water stress conditions to determine the effect of water stress on plant water relations and canopy temperature depression of potato. Of the five genotypes, CIP 393371.58 and CIP 396244.12 maintained higher relative water content (RWC) under both the conditions and showed comparatively less midday depression in RWC. The water stress condition significantly decreased water uptake capacity. Under water stress condition tolerant genotypes CIP 393371.58 and CIP 396244.12 showed highest xylem exudation rate of 0.26 and 0.18 g h−1, respectively and transpiration rate of 36 and 34 µg m−2 s−1, respectively at 50 days after planting, and both were positively and significantly correlated. Greater increases in canopy temperature were observed at noon in Asterix and CIP 391004.18 and lower in CIP 393371.58 and CIP 396244.12 and showed inverse relationship with transpiration rate. The genotypes CIP 393371.58 and CIP 396244.12 showed higher canopy temperature depression value and the genotypes CIP 391004.18 and Asterix showed lower canopy temperature depression value under water stress condition. Among the genotypes, CIP 393371.58 and CIP 396244.12 showed better tolerance to water stress condition.

Features of CAM-cycling expressed in the dry season by terrestrial and epiphytic plants of Clusia arrudae Planchon & Triana in two rupestrian savannas of southeastern Brazil in comparison to the C3-species Eremanthus glomerulatus Less.

In rupestrian savannas in southeastern Brazil Clusia arrudae Planchon & Triana in the dry season performed CAM-cycling with very little gas exchange in the early morning followed by a long depression during the rest of the day. CAM-cycling is considered as a survival strategy under drought and the productivity of the plant which is quite abundant must rely on performance of C 3 -photosynthesis in more favorable seasons. In rupestrian savannas in the Serra do Cipo (19°14′48.9″S, 43°30′36.0″W) at 1300 m a.s.l. and in the Serra de Sao Jose (21°08′S, 44°17′W) at 1010–1030 m a.s.l. in southeastern Brazil Clusia arrudae Planchon & Triana is abundant. As CAM is frequent in the genus Clusia we supposed that it would perform CAM as a drought adaptation at the very dry rupestrian savanna sites in the dry season. At the Serra do Cipo site as control we studied the obligate C3-species Eremanthus glomerulatus Less. Both species are sympatric at this site. Eremanthus glomerulatus performed C3-photosynthesis with a midday depression. The patterns of C. arrudae were completely different so that genuine C3-photosynthesis was excluded, but they were also not typical of CAM. The stomata were almost closed during the night. Some stomatal opening and net CO2 uptake occurred in the early morning hours followed by a long depression with stomatal closure throughout the rest of the day. Nevertheless, photo inhibition was limited and photosynthetic electron transport rate remained high during this time indicating that photosynthetic excitation energy was required and suggesting that CO2 assimilation was continuing behind closed stomata based on internal sources of CO2. There was some nocturnal accumulation of organic acids (malic and citric acids) which could represent a source of CO2 during the light period. Overall, the observations can be best explained by the performance of CAM-cycling by C. arrudae. However, leaf carbon gain of C. arrudae was much inferior to that of E. glomerulatus. CAM-cycling appears to be a strategy for protection from photoinhibitory damage and survival under strong conditions of drought. Steeper more vertical leaf positions observed would assist reducing overheating during stomatal closure at high irradiance. The abundance of C. arrudae suggests that the plant must have other means to sustain productivity such as full C3-photosynthesis in the more favorable seasons.

Stomatal Conductance Is Essential for Higher Yield Potential of C3 Crops

The present review of gas-exchange studies conducted in rainfed or irrigated field conditions clearly indicates that stomatal conductance (gs) of major crops has been inadvertently increased in the last 50 to 80 years as higher yields were being reached through conventional plant breeding. These findings suggest that high gs rates are critical to optimum growth and yield of modern crops, in particular to crop growth rate (CGR) during seed formation and filling. Several hypotheses are presented that may account for this increase. This review also includes studies in which increases in gs were documented for genetically-engineered plants. However, field evaluations of their gas-exchange performance remain sparse. The main finding of this review is that higher rates of gs should be sought, as we forego the usual consideration of crop plants as single organisms losing water, but rather acknowledge that water does exit a crop canopy along a Soil Plant Atmosphere Continuum (SPAC). In non-limiting or moderately-limiting soil water conditions, high yields are generated by an active SPAC that requires sustained levels of gs. In conditions of high evaporative demand, as in summer afternoons, sustained gs allows for cooler canopies with no mid-day depression in photosynthesis as CO2 remains able to diffuse in the leaf through stomata.

Diurnal and seasonal variations in photosynthetic characteristics of switchgrass in semiarid region on the Loess Plateau of China

In order to use rationally switchgrass (Panicum virgatum L.) introduced in a large scale in semiarid regions on the Loess Plateau of China, we investigated and compared soil water storage dynamics, diurnal and seasonal changes in leaf photosynthetic characteristics, and biomass production of switchgrass grown under three different row spacing (20, 40, and 60 cm). Results indicated that photosynthetic parameters showed a pronounced seasonality. Diurnal course of net photosynthetic rate (PN) was bimodal, showing obvious midday depression, which was mainly due to stomatal limitation in May and June, by nonstomatal limitation in August, and both stomatal and nonstomatal factors in September. Generally, PN, stomatal conductance, instantaneous water-use efficiency, light-saturated net photosynthetic rate, saturation irradiance, and compensation irradiance increased with increasing row spacing. Plant height, leaf width, and a relative growth rate of biomass accumulation were significantly higher at the row spacing of 60 cm, while 20 cm spacing showed significantly higher aboveground biomass production and the biomass water-use efficiency. All these confirmed that soil water is the key limiting factor influencing switchgrass photosynthesis, and suggested that the wide row plantation (i.e., 60 cm) was more beneficial to switchgrass growth, while narrow spacing was in favor of improving switchgrass productivity and water-use efficiency.

Diurnal depression in leaf hydraulic conductance at ambient and elevated [CO2] reveals anisohydric water management in field-grown soybean and possible involvement of aquaporins

Diurnal cycles of photosynthesis and water use in field-grown soybean (Glycine max) are tied to light intensity and vapor pressure deficit (VPD). At high mid-day VPD, transpiration rates can lead to a decline in leaf water potential (Ψleaf) if leaf hydraulic conductance (Kleaf) is insufficient to supply water to intercellular airspaces in pace with demand. Kleaf is determined by leaf xylem conductivity to water, as well as extra-xylem pathways that are likely mediated by aquaporin water transport proteins. When transpiration demand exceeds the maximum capacity of Kleaf to supply water, high tension in the water column can cause cavitation in xylem, and these emboli-blocked xylem vessels reduce water transport and thus lower Kleaf. Stomatal conductance typically remains high at mid-day for soybean, suggesting either a mid-day increase in Kleaf or that photosynthesis may be maintained at the cost of leaf water status, indicative of an anisohydric water management strategy in soybean. This study examined diurnal fluctuations in Kleaf and Ψleaf, showing a mid-day depression in Kleaf in a pattern closely reflecting that of Ψleaf, indicating that Kleaf depression is the result of cavitation in leaf xylem. The diurnal depression of Kleaf was not prevented by growth at elevated [CO2], which lowered stomatal conductance. Diurnal transcription patterns of aquaporin genes showed that a total of 34 genes belonging to 4 aquaporin families were expressed in soybean leaves, of which 22 were differentially expressed between at least two time points. These data suggest that mid-day Kleaf depression was driven primarily by cavitation at increasing xylem water tensions, but that aquaporins are also likely involved in diurnal regulation of soybean leaf water status. It is further concluded that because soybean photosynthesis is typically sustained at mid-day, Kleaf even at the depressed level was in excess of that needed to sustain a stomatal conductance sufficient to prevent depression of photosynthesis in soybean.

克里雅河流域荒漠-绿洲交错带3种不同生活型植物的光合特性

PDF HTML阅读 XML下载 导出引用 引用提醒 克里雅河流域荒漠-绿洲交错带3种不同生活型植物的光合特性 DOI: 10.5846/stxb201310302623 作者: 作者单位: 中国科学院新疆生态与地理研究所,新疆大学资源与环境科学学院,中国科学院新疆生态与地理研究所,新疆大学资源与环境科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然基金新疆联合项目(U1138303); 国家自然科学基金项目 (31000166, 31260112) Photosynthetic characteristics of three different life-form plants in the desert-oasis ecotone of Keriya River Basin Author: Affiliation: Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences,College of Resources and Environment Science, Xinjiang University,,College of Resources and Environment Science, Xinjiang University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用LI-6400光合仪测定新疆克里雅河流域荒漠-绿洲交错带自然生长的芦苇、柽柳、胡杨叶片的气体交换参数及环境影响因子,通过对比3种植物光合特性的差异及其与环境因子间的关系,探讨3种植物对荒漠环境的适应特性和机制。结果表明:(1) 3种植物叶片Pn日变化均呈不对称的双峰曲线,"午休"现象明显,Pn日均值的大小依次为胡杨> 芦苇> 柽柳,种间差异不显著。(2) Tr、PAR和Gs与3种植物Pn的日变化存在极显著或显著的相关关系,其中影响芦苇Pn的主要因子是Tr、PAR和Gs,作用效应为Tr > Gs > PAR;影响柽柳Pn的主要因子是Tr、Gs,作用效应为Tr > Gs;影响胡杨Pn的主要因子是Tr。(3) 3种植物的光合作用对光强和CO2的响应特征可用二次方程描述;光补偿点和饱和点均为柽柳> 胡杨> 芦苇;CO2补偿点为胡杨> 柽柳> 芦苇,饱和点为胡杨> 芦苇> 柽柳。(4) 3种植物的表观量子效率在0.0341-0.0411 mol/mol之间,羧化效率在0.0480-0.0546 mol m-2 s-1之间。综合比较表明,3种干旱区植物在自然条件下日均净光合速率、光能利用率和CO2同化能力差异不显著,气孔限制是光合"午休"现象产生的主要原因;影响3种植物光合作用的主导因子各不相同,但Tr与Pn间的关系较其它因子更为密切。 Abstract:Vegetation plays an important role in preventing wind erosion, sand fixation, water conservation and ecosystem restoration in oasis ecosystem. For the photosynthetic characteristics could fairly reflect the adaptation of plants to their habitat, gas exchange parameters and environmental factors of three different life-form plants which grown in the desert-oasis ecotone of Keriya River Basin were measured. By comparing the photosynthetic characteristics of Phragmites australis, Tamarix ramosissima, Populus euphratica and their relationship with environmental factors, adaptive capacities and mechanisms of the three different life-form plants were discussed. The results were as follow: The diurnal variation in net photosynthetic (Pn) rate of the three plants showed two peaks, which displayed remarked photosynthetic "midday depression". The order of the average values of Pn was: P. euphratica > P. australis > T. ramosissima. However, there was no significant difference among them. The analysis of partial correlation and path on Pn and environmental factors showed that the diurnal variation of Pn had significant correlation with transpiration rate (Tr), photosynthetically active radiation (PAR), and stomatal conductance (Gs), respectively. Tr, PAR and Gs were the main factors which affected Pn of P. australis and the order of effecting ability was Tr > Gs > PAR. Tr, and Gs were the main factors which affected Pn of T. ramosissima and the order of effecting ability was Tr> Gs. Tr was the only main factor which affected Pn of P. euphratica. For the three kinds of plants, the Pn-PAR response curves and Pn-CO2 response curves had the same changing tendency, which could be quantitatively described by quadratic equation, respectively. The order of light compensation points and light saturation points were both T. ramosissima > P. euphratica > P. australis. The order of carbon dioxide compensation points was P. euphratica > T. ramosissima > P. australis and the order of saturation points were P. euphratica > P. australis> T. ramosissima. The apparent quantum yield and carboxylation efficiency of these three plants were varied from 0.0341 to 0.0411 mol/mol and 0.0480 to 0.0546 mol m-2 s-1 on daily basis, respectively. The results indicated that the average net photosynthetic rate, energy efficiency and CO2 assimilation capacity were not significantly different among the three kinds of plants, and the photosynthetic "midday depressions" was mainly resulted from stomatal limitation. The main factors which affected physiological process of photosynthesis are different among the three different life-form plants, but the relationship between Tr and Pn is closer than other factors. 参考文献 相似文献 引证文献

千岛湖次生林优势种植物光合生理生态特性

The main factors that influence community succession in an evergreen broadleaf forest are differences in the ecological adaptability and eco-physiological traits of the various dominant plant species.Studies of the eco-physiological traits of these dominant species allow researchers to better understand the physiological demands and ecological traits of dominant species in their forest habitat and these studies also help researchers to recognize and understand the intrinsic mechanisms involved in forest regeneration and the mechanisms driving ecological succession in an evergreen broadleaf forest at the individual species level.In this study,we used a portable photosynthesis system to determine various physiological parameters associated with plant growth.We investigated the seasonal dynamics of the diurnal variations of photosynthesis,the responses to both light and CO2,and the relative chlorophyll content of the dominant plant species in the secondary forest surrounding Qiandao Lake,Zhejiang,China.The species included Pinus massoniana,Castanopsis sclerophylla,Lithocarpus glaber and Cyclobalanopsis glauca.The results showed the following.(1) Diurnal variations of the net photosynthesis rate(Pn) of P.massoniana exhibited a monomodal curve in all four seasons,while the variations in PnforC.sclerophylla were bimodal in August but had a single curve in the other three time seasons investigated.Diurnal variations of Pnof L.glaber and C.glauca exhibited a typical bimodal curve with obvious "midday depression"in May,August and November but had a monomodal curve in February.(2) The diurnal integral values of Pnof P.massoniana and C.sclerophylla were significantly higher in August than those in the other three seasons,while those of L.glaber and C.glauca were significantly higher in November than those in the other three time periods investigated.The average value of the diurnal integral value of Pnin the four dominant species differed significantly in all four seasons and was ranked in the order of:P.massoniana C.sclerophylla L.glaber C.glauca;(3) Compared with the other three dominant species,for P.massoniana,the light saturation point(LSP),light compensation point,maximum net photosynthetic rate,dark respiration rate(Rd),maximum rate of carboxylation and maximum rate of electron transport were highest in all four seasons,while the apparent quantum yield(AQY) was the lowest.The LSP and Rdof C.glauca were the lowest,while the AQY of C.glauca was the highest in the four seasons.Photosynthetic characteristics of C.sclerophylla and L.glaber were moderate among the four species.(4) In all four seasons,the relative chlorophyll content of C.glauca was the highest among the four dominant species,while that of P.massoniana was the lowest.All these results indicate that P.massoniana and C.sclerophylla are shade intolerant species and moderately shade intolerant species,respectively,while L.glaber and C.glauca are strongly shade tolerant species,although C.glauca is more strongly shade tolerant when compared with L.glaber.Based on these findings,we concluded that P.massoniana and C.sclerophylla will withdraw from the community during the succession.L.glaber and C.glauca will become the dominant species in the secondary forest surrounding Qiandao Lake as these forests mature.

Occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees distributed in a South-east Asian tropical rainforest in Peninsular Malaysia.

In this study, we demonstrated the occurrence of stomatal patchiness and its spatial scale in leaves from various sizes of trees grown in a lowland dipterocarp forest in Peninsular Malaysia. To evaluate the patterns of stomatal behavior, we used three techniques simultaneously to analyze heterobaric or homobaric leaves from five tree species ranging from 0.6 to 31 m in height: (i) diurnal changes in chlorophyll fluorescence imaging, (ii) observation and simulation of leaf gas-exchange rates and (iii) a pressure-infiltration method. Measurements were performed in situ with 1000 or 500 μmol m(-2) s(-1) photosynthetic photon flux density. Diurnal patterns in the spatial distribution of photosynthetic electron transport rate (J) mapped from chlorophyll fluorescence images, a comparison of observed and simulated leaf gas-exchange rates, and the spatial distribution of stomatal apertures obtained from the acid-fuchsin-infiltrated area showed that patchy stomatal closure coupled with severe midday depression of photosynthesis occurred in Neobalanocarpus heimii (King) Ashton, a higher canopy tree with heterobaric leaves due to the higher leaf temperature and vapor pressure deficit. However, subcanopy or understory trees showed uniform stomatal behavior throughout the day, although they also have heterobaric leaves. These results suggest that the occurrence of stomatal patchiness is determined by tree size and/or environmental conditions. The analysis of spatial scale by chlorophyll fluorescence imaging showed that several adjacent anatomical patches (lamina areas bounded by bundle-sheath extensions within the lamina) may co-operate for the distributed patterns of J and stomatal apertures.

Orchid Conservation in Singapore under Natural Conditions: Responses of Grammatophyllum Speciosum to Growth Irradiances

Grammatophyllum speciosum orchid plants were grown both on the ground and on trees under high light (HL) and low light (LL) conditions in Pasir Ris Park, Singapore. This paper studied photosynthetic energy utilization investigated by chlorophyll (Chl) fluorescence and photosynthetic pigments; plant water status measured by leaf relative water content (RWC) and stomatal conductance (gs). All plants had midday leaf RWC greater than 80%, indicating no severe water deficit occurred in any plants. Except for plants grown on trees under LL, midday depression of Fv/Fm ratios occurred in all other plants, indicating dynamic photoinhibiton. There was no chronic photoinhibition in any plants as Fv/Fm ratios recovered to healthy level at early morning. Grown on the ground under HL, G. speciosum had higher photochemical quantum yield (ΔF/Fm’), greater electron transport rate (ETR) and non-photochemical quenching (NPQ), indicating their higher efficiency in utilization and dissipation excess energy. Plants grown on the ground under HL had lower Chl and Chl/Car ratio, but higher content of carotenoids and Chl a/b ratio compared to the other plants, implying their acclimation to HL conditions. The highest gs was recorded at 1000 h, suggesting the avoidance of drought stress by widely opening stomata only for a short period of time in the early morning. Higher gs was related to higher leaf temperature, indicating that the role of gs in moderating leaf temperature. Understanding the effects of growth irradiance on photosynthesis of G. speciosum would be an important step towards a sustainable conservation of native orchids in Singapore.