木荷种源间光合作用参数分析

Aims Our objectives were to find the optimal models for different drought stresses by comparing four light response models of photosynthesis in leaves of Periploca sepium growing in sand formed from seashells, investigate the adaptability law of parameters of light response models to drought stresses, and define the adaptability of P. sepium to the shell sand moisture conditions. Methods We used three-year-old P. sepium grown in shell ridge island of China’s Yellow River Delta as experimental material, set up four moisture conditions simulating those in shell sand, measured light responses of photosynthesis in leaves of P. sepium under different drought stresses using CIRAS-2 portable photosynthesis system, and fitted and analyzed the light response curves by four models: rectangular hyperbola, non-rectangular hyper-bola, exponential and modified rectangular hyperbola. Important findings The sequence of fitting effect of the four light response models was in descending order: modified rectangular hyperbola model nonrectangular hyperbola model exponential model rectangular hy-perbola model. This result was related to the latter three models not having extreme values, not fitting the process of light response curve declining after light saturation point (LSP), and not directly and accurately solving maxi-mum net photosynthetic rate (Pnmax) and LSP. Among them, the non-rectangular hyperbola model best fit dark respiration rate (Rd), the rectangular hyperbola model best fit light compensation point (LCP) and modified rectangular hyperbola model best fit Pnmax and LSP. The adaptabilities of the four models to different drought stresses varied. The modified rectangular hyperbola model well fit the curves under all the drought stresses, the rectangular hyperbola model and exponential model suited mild drought stress and the non-rectangular hyperbola model suited severe drought stress. The light response parameters, including apparent quantum yield (AQY), Rd, LCP, Pnmax and LSP, responded to drought stresses differently. AQY, Rd and LCP first increased and then decreased with the aggravation of drought stress, while Pn, Pnmax and LSP decreased gradually. LSP decreased by 5.2%, 16.3% and 34.55% under light stress, moderate stress and severe stress, respectively, in comparison to the control (1556 μmol·m–2·s–1). Pnmax decreased by 17.8%, 39.0% and 59.0% compared to the control (22.58 μmol·m–2·s–1). Light use capability of P. sepium leaf was strongest and light ecological amplitude (1520 μmol·m–2·s–1) was wid-est under sufficient water condition; photo-saturation and photo-inhibition occurred significantly, light use capa-bility weakened, and photosynthetic capacity was inhibited seriously under severe stress.

Rectangle hyperbola model (RH), nonrectangle hyperbola model (NRH), exponential model (EM), modified rectangle hyperbola model (MRH), and modified exponential model (MEM) were applied respectively for modeling the photosynthesis-light response curves (PLC) based on four types of curves (photosynthesis-light response curve of inhibition, PLCi, photosynthesis-light response curve of saturation, PLCs, photosynthesis-light response curve of unsaturation, PLCu andphotosynthesis-light response curve in weak light, PLCw) in canopy of 15 years old planted Larix olgensis tree in the Maoershan Forest Farm, Heilongjiang Province. The major photosynthetic physiological indexes including maximum net photosynthetic rate (Pn max), dark respiration rate (Rd), light compensation point (LCP), light saturation point at saturated light intensity (LSP) and apparent quantum yield (AQY) were calculated. All the five candidate models were comprehensively compared by the model goodness-of-fit and the precision estimations of photosynthetic physiological indexes in the four types of curves. The results showed that MEM model was only suitable for fitting the PLCi. MRH model showed the best goodness-of-fit for PLCi and PLCs(Ra2was 0.9986 and 0.9978, respectively). Meanwhile, NRH model expressed the best fitting result in PLCu and PLCw (Ra2 was 0.9996 and 0.9963, respectively). MRH had the lowest mean absolute value of relative error (MAPE) when evaluating Pn max in different types of curves (0.1%<MAPE<0.7%), but its precision estimation for LCP was relatively worse (2.5%<MAPE<9.4%). NRH model exhibited more accurate estimation for LCP of PLCs and PLCu, as well as Rd of PLCu(MAPE was 1.8%, 0.1%, and 3.9%, respectively). RH model represented better prediction effect for LCP of PLCi and Rd of PLCs(MAPE was 1.0% and 2.7%, respectively). EM was more sui-table for estimating LCP of PLCw(MAPE was 0.2%). Comprehensive analysis showed that MRH model not only proved well model goodness-of-fit and accurate estimation of photosynthetic physiological indexes, but also showed the highest stability when fitting different types of curves. As a result, MRH model was finally selected as the optimal canopy photosynthesis-light response model of planted L. olgensis tree.

PDF HTML阅读 XML下载 导出引用 引用提醒 千岛湖次生林优势种植物光合生理生态特性 DOI: 10.5846/stxb201306041323 作者: 作者单位: 台州学院生态研究所,台州学院生态研究所,台州学院生态研究所;上海师范大学生命与环境科学学院,台州学院生态研究所;上海师范大学生命与环境科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 浙江省自然科学基金项目(Y507660); 台州学院培育基金资助项目(2013PY21) Photo-ecological characteristics of the dominant plant species in the secondary forest surrounding Qiandao Lake, Zhejiang, China Author: Affiliation: Institute of Ecology,Taizhou University,Institute of Ecology,Taizhou University,Institute of Ecology,Taizhou University;China;College of Life and Environmental Sciences,Shanghai Normal University;China,Institute of Ecology,Taizhou University;China;College of Life and Environmental Sciences,Shanghai Normal University;China 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:对千岛湖次生林优势种马尾松(Pinus massoniana)、苦槠(Castanopsis sclerophylla)、石栎(Lithocarpus glaber)、青冈(Cyclobalanopsis glauca)在不同季节的光合作用日变化、光响应、CO2响应以及相对叶绿素含量进行了分析,以期了解群落演替的内在机制。结果表明:(1)马尾松的净光合速率(Rn)日变化在4个季节均呈"单峰"曲线;苦槠在8月呈"双峰"曲线,其他3个月份均呈"单峰"曲线;石栎和青冈在5月、8月和11月的Rn日变化均为"双峰"曲线,有明显的光合"午休"现象,2月为"单峰"曲线。(2)马尾松和苦槠的Rn日积累值为8月最高,石栎和青冈为11月最高,且均与其他3个月均差异显著。4种优势种在4个季节的Rn日积累值的平均值大小为马尾松 > 苦槠 > 青冈 > 石栎,差异显著。(3)4个季节中,光饱和点(LSP)、光补偿点(LCP)、最大净光合速率(Amax)、暗呼吸速率(Rd)、最大羧化速率(Vcmax)、最大电子传递速率(Jmax)均以马尾松最高,表观量子效率(AQY)为马尾松最低。青冈在4个季节中具有最低的LSP、Rd和最高的AQY。苦槠和石栎的光合特性介于马尾松和青冈之间。(4)相对叶绿素含量以青冈最高,马尾松最低。总之,马尾松属强阳性树种,苦槠为阳性树种,石栎具有一定的耐荫性,青冈的耐荫性较强。 Abstract: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 (Rn) of P. massoniana exhibited a monomodal curve in all four seasons, while the variations in Rn for C. sclerophylla were bimodal in August but had a single curve in the other three time seasons investigated. Diurnal variations of Rn of 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 Rn of 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 Rn in 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 Rd of 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. 参考文献 相似文献 引证文献

The study analyzed the variations of physiological, morphological and anatomical leaf traits during its development in Corylus avellana L. saplings. Three different phases were identify during leaf development: the first phase (hereafter IP) considered in the developing leaves, the second phase (IIP) in the mature green leaves and the third phase (IIIP) in the senescent leaves. In particular, variations in parameters estimated from the photosynthetic light response curves, in chlorophyll fluorescence variables and in morphological leaf traits were analyzed during the three phases. The principal component analysis (PCA) carried out using all the considered morphological characters (leaf mass per area - LMA, and leaf tissue density - LTD) and physiological traits (the maximum net photosynthetic rates - ANmax, dark respiration rates - RD, light compensation point - LCP, light saturation point – LSP, maximum quantum yield - ɸmax, fluorescence-based maximum quantum yield of PSII photochemistry - Fv/FM and effective quantum yield of PSII photochemistry - ɸPSII) showed a complete separation among the considered phases. The results showed that the major differences occur between the phases IP and IIP. In particular, a greater variation was found for LMA, ANmax, RD. On the contrary a lower variation was observed for ɸmax which remain quite constant from IP to IIP indicating that chloroplasts present in juvenile leaves are fully functional.

Abstract: The hybrid Azadirachta indica × Melia azedarach is a new plant variety that was obtained through somatic hybridization. The plant could grow normally in regions with an average annual temperature of 15 °C, and it had a higher concentration of active insecticidal substance in its seeds. Therefore, the hybrid will likely become a valuable new tree species in subtropical and warm temperate regions. However, the photosynthetic physiological characteristics of A. indica × M. azedarach remain unknown. The photosynthetic gas exchange of the hybrid at three different ages (one year old (AM1), three years old (AM3), and five years old (AM5)) were measured. The specific leaf mass per area (LMA), leaf N, leaf P, and leaf N/P of each tree sample were measured, and the photosynthetic N and P use efficiencies (PNUE and PPUE, respectively) were also calculated. The maximum leaf net photosynthetic rate Pa (based on area), Pm (based on mass), light saturation point (LSP), light compensation point (LCP), stomatal conductance (gs), and transpiration rate (Tr) of A. indica × M. azedarach decreased with increasing tree age, whereas the instantaneous water use efficiency (WUE) increased with age. The photosynthetic capacity showed no significant differences between AM3 and AM5 but was significantly higher in AM3 and AM5 when compared with AM1.The Pa, Pm, apparent quantum yield (AQY), LSP, gs, and Tr of A. indica × M. azedarach were significantly lower than that of the parental M. azedarach, whereas the dark respiration rate (Rd) and WUE were significantly higher than that of M. azedarach. A reduction in the maximal photosynthetic rate of A. indica × M. azedarach that was observed with increased age was primarily related to the increased LMA and the decline in leaf nitrogen (N) and leaf phosphorus (P) concentrations. Additionally, the decline in stomatal conductance (gs) was also an important factor leading to age-dependent reductions in the photosynthetic rate. These findings suggest that the tree’s age has a significant impact on A. indica × M. azedarach gas exchange during juvenile stages, and the photosynthetic capacity of the hybrid was significantly lower than that of the parental M. azedarach.

Leaf traits and physiology are species-specific and various with canopy position and leaf age. Leaf photosynthesis, morphology and chemistry in the upper and lower canopy positions of Pinus koraiensis Sieb. et Zucc and Quercus mongolica Fisch. ex Turoz in broadleaved Korean pine forest were determined in September 2009. Canopy position did not significantly affect light-saturated photosynthetic rate based on unit area (P area) and unit dry mass (P mass), apparent quantum yield (α), light compensation point (LCP), light saturation point (LSP); total nitrogen (Nm), phosphorus (Pm), carbon (Cm), and chlorophyll content (Chlm) per unit dry mass; leaf dry mass per unit area (LMA) and photosynthetic nitrogen-use efficiency (PNUE) for P. koraiensis current-year needles and Q. mongolica leaves. While in P. koraiensis one-year-old needles, P area, P mass, α and LCP in the upper canopy were lower than those in the lower canopy. The needles of P. koraiensis had higher Cm and LMA than leaves of Q. mongolica, but P mass, Chlm and PNUE showed opposite trend. There were no differences in P area, LSP, Nm, and Pm between the two species. Needle age significantly influenced photosynthetic parameters, chemistry and LMA of P. koraiensis needles except LCP, LSP and Cm. In contrast to LMA, P area, P mass, Nm, Pm, Chlm, and PNUE of one-year-old needles were significantly lower than those of current-year needles for P. koraiensis. The negative correlations between LMA and P mass, Nm, Pm, Chlm, and positive correlations between P mass and Nm, Pm, Chlm were found for P. koraiensis current-year needles and Q. mongolica leaves. Our results indicate that leaf nitrogen and phosphorus contents and nutrient absorption from soil are similar for mature P. koraiensis and Q. mongolica growing in the same environment, while difference in carbon content between P. koraiensis and Q. mongolica may be attributed to inherent growth characteristics.

Present study was conducted to explore the growth and photosynthetic characteristics of Tulipa edulis under different light conditions (23%, 45%, 63%, 78%, 100% of full sunlight) and to determine the optimum light intensity for growth of T. edulis. The leaf area and biomass indicators as well as reproductive characteristics were measured. The photosynthetic basic parameters and light response curve were determined by a LI-6400XT portable photosynthesis system, and the light response curve characteristic parameters was determined. Additionally, chlorophyll fluorescence parameters were determined by assorted fluorescence leaf chamber of LI-6400XT. The lowest biomass yield was observed in the 23% and 100% of full sunlight treatments while the highest value was found under the 78% of full sunlight conditions. With the reduction of light availability, the success rate of sexual reproduction, light saturation point (LSP) and light compensation point (LCP) reduced, while apparent quantum yield (AQY) increased. 23% and 45% of full sunlight treatments led to lower photosynthesis rate (Pn) and higher apparent quantum yield (AQY) in comparison with other treatents. The highest photosynthesis rate was observed in the 78% and 100% of full sunlight treatments. In addition, 78% of full sunlight treatments led to highest Fv/Fm, Fv'/Fm', PhiPS II, ETR, and qP. T. edulis was able to adapt in a wide range of light intensity, and 78% of full sunlinght was the most suitable light condition for growth of T. edulis.

<p indent=0mm>As light interception and leaf water shedding may require different leaf traits, trade-offs may exist between the leaves’ abilities in light interception and leaf water shedding. Moreover, such trade-offs may vary with the vertical canopy position as leaf traits vary with tree height. We studied the variations in leaf traits at different canopy positions to study how canopy positions would affect the trade-off between the traits related to light interception and leaf water shedding in subtropical broad-leaved trees. We used the standardized major axis regression method to analyze the relationships among leaf morphological traits (leaf thickness and leaf length/width ratio), configuration traits (leaf angle and leaf drip tip length), and physiological traits (photosynthesis-light saturation point and photosynthesis-light compensation point) between sun and shade leaves. The results are as follows: (i) There was no significant difference in the leaf thickness and leaf length/width ratio at different canopy positions (<italic>P</italic>>0.05). The leaf angle (34.92°±1.15°), light saturation point ((954.89±27.86) µmol/(m²·s)), and light compensation point ((29.45±1.02) µmol/(m²·s)) at the upper canopy were significantly higher than those at the lower canopy (leaf angle: 16.66°±0.50°, light saturation point: (520.74±15.47) µmol/(m²·s), and light compensation point: (12.54±0.38) µmol/(m²·s); <italic>P<</italic>0.05). However, the leaf drip tip length was significantly shorter at the upper canopy position ((4.26±0.15) mm) than at the lower canopy position ((7.18±0.22) mm; <italic>P</italic><0.05). (ii) There were significant correlations among leaf angle, leaf drip tip length, light saturation point, and light compensation point at different canopy positions (<italic>P</italic><0.05), but the leaf drip tip length and leaf length/width ratio were only weakly correlated at the upper canopy leaves (<italic>P</italic><0.05). (iii) Common slope (<italic>P</italic>>0.05) and isometric scaling existed among the leaf angle, light saturation point, and light compensation point at different canopy positions, but there was no common constant (<italic>P</italic><0.05). These results indicated that the canopy position does not alter the trade-off strategy between light interception and leaf water shedding. The leaf drip tip length and inclination were mainly affected by the light saturation point and light compensation point.

Ongoing climate change is projected to intensify drought stress globally. Understanding the response mechanisms of Phyllostachys edulis (Carrière) J. Houz. (moso bamboo) to long-term drought is crucial, given its significance as a carbon sequestration resource. In this study, precipitation exclusion was implemented to simulate drought stress and we investigated the effects of long-term drought on the photosynthetic parameters, stomatal conductance, and water use efficiency of moso bamboo. The results showed that throughout all growth seasons, the maximum net photosynthetic rates (Pmax) of bamboo at all ages under long-term drought conditions (after 8 years of precipitation exclusion treatment) were significantly lower than those of the control (p &lt; 0.05). It can be concluded that long-term drought reduced the maximum photosynthetic capacity of the bamboo at all ages. Under long-term drought conditions, there were many seasons where the light saturation point (LSP) of first-degree (1–2 years old) bamboo and third-degree (5–6 years old) bamboo under drought was significantly lower than those of the control, while the LSP value of second-degree (3–4 years old) bamboo under drought was significantly higher than that of the control. This suggests that long-term drought reduced the ability of first-degree and third-degree bamboo to utilize strong light, while improving the ability of second-degree bamboo to utilize strong light in summer, autumn, and winter. Under long-term drought conditions, the light compensation point (LCP) and the apparent quantum efficiency (AQY) of the bamboo decreased. It can be concluded that long-term drought reduced the ability of first-degree bamboo to utilize weak light in all seasons, as well as the ability of second-degree bamboo to utilize weak light in spring and autumn; meanwhile, it improved the ability of second-degree bamboo to utilize weak light in summer and winter, and the ability of third-degree bamboo to utilize weak light in spring, summer, and autumn. In the high light range (PARi &gt; 1000 µmol · m−2 · s−1), there were significant differences in stomatal conductance (gs) among different the different treatments of bamboo, which were influenced by both the growing season and the forest age. Compared to the control, under drought conditions, the stomatal conductance of third-degree bamboo increased in spring and that of the second-degree bamboo increased in autumn. The correlation analysis showed that the relationship between the stomatal conductance and vapor pressure deficit (VPDL) of bamboo under long-term drought conditions showed a significant polynomial relationship in both high and low light ranges. The correlation between the instantaneous water use efficiency (iWUE) and VPDL for the drought and control treatments of bamboo also showed a significant polynomial relationship in high light ranges. It was found that long-term drought changed the photosynthetic parameters of the bamboo, reflecting its ability to tolerate and adapt to drought in different seasons. Age-related differences in photosynthetic parameters should be fully considered in forest age structure adjustments and forest thinning procedures to strengthen the light intensity and maintain the opening of the stoma. These results provide a theoretical basis for the efficient and sustainable cultivation of bamboo under global climate change.

<title>Abstract</title> Functional plant traits are essential indicators of biodiversity conservation and ecosystem management. Understanding the relationships among leaf traits allows for the estimation of difficult-to-measure traits from those that are easier to quantify and widely distributed. This approach enhances the ability to analyze trait variation, identify scaling relationships, and address constraints in estimating plant-atmosphere carbon exchange. However, research on the correlation between photosynthetic capacity and leaf traits remains limited. Therefore, this study aims to explore the differences and correlations between leaf traits and photosynthetic capacity parameters across different growth forms. In this study, the leaf traits in 21 dominant woody species from a subtropical evergreen broad-leaved forest in southwestern China were assessed. Key photosynthetic parameters, including the maximum net photosynthetic rate, apparent quantum yield, light compensation point, and light saturation point, were investigated. Additionally, leaf traits such as leaf tissue density, leaf dry matter content, specific leaf area (SLA), leaf area, chlorophyll content, carbon content per unit leaf area, nitrogen content per unit leaf area (Narea), and carbon-to-nitrogen ratio were analyzed. Overall, no significant variations in maximum photosynthetic rate or photosynthetic quantum efficiency were observed between tree and shrub species in this forest. Shrub species exhibited greater adaptability and compensatory capacity to light conditions during photosynthesis. Using multiple linear regression models, SLA was identified as the key structural trait and Narea as the primary chemical trait for predicting the photosynthetic capacity of woody plants in this region. Nevertheless, for different growth forms, selecting optimal parameters for classification modeling in abiotic predictive models of photosynthetic capacity is recommended to improve prediction accuracy for subtropical evergreen broad-leaved forest plants.

To get better insight into the photosynthetic mechanism of plant adaptation to strong light in intercropped maize, a field trial was carried out in 2014-2015 to investigate the effects of maize/peanut intercropping row ratio and phosphate fertilizer on diurnal variation in light intensity of maize canopy, SPAD value, and the curves of photosynthetic response of net photosynthetic rate (Pn) to photon flux density (PFD) and to CO2 of functional leaves. The field trial comprised 2 rows maize intercropped with 2 rows peanut (2:2, R1), 2 rows maize intercropped with 4 rows peanut (2:4, R2) and 2 rows maize intercropped with 8 rows peanut (2:8, R3). Results showed that the light intensity of intercropped maize canopy was R3>R2>R1. From pre-tasselling to filling stage, the SPAD value, apparent quantum efficiency (AQY), light compensation point (LCP), light saturation point (LSP), maximum net photosynthetic rate, carboxylation efficiency (CE), maximum electron transfer rate (Jmax), triose phosphate utilization (TPU), stomatal conductance (gs), transpiration rate (Tr) and Pn in ear leaves of intercropped maize were R3>R2>R1, but the intercellular CO2 concentration (Ci) was R1>R2>R3. At dough stage, the AQY, LSPn, gs, CE, Jmax and TPU in ear lea-ves of intercropped maize in R3 intercropping system were lower than those in R2 intercropping system. The photosynthetic indices, such as AQY, LSPn, CE, Vc max, Jmax and TPU were increased by phosphate fertilizer application. These results suggested that the key mechanisms that enhanced strong light utilization ability of intercropped maize were attributed to gradual improvement in gs, AQY, CE, Vc max, Jmax and TPU of ear leaves with increasing light intensity, however, beyond a certain light intensity, intercropped maize leaves were prone to premature senescence. Nonetheless, phosphate fertilizer could improve light utilization and delay leaf senescence in intercropped maize.

Effective irrigation can maintain the vigorous photosynthetic metabolism of leaves and lay a physiological foundation for their material production. Dry matter accumulation and leaf response to light and carbon dioxide of maize under irrigation quotas of 50 mm (Q0), 90 mm (Q1), 170 mm (Q2) and 250 mm (Q3) were studied. The results showed that the dry matter accumulation were significantly increased in Q2 and Q3 treatment compared with CK at R3, R4 and R6 stages. With the increase of light intensity, the photosynthesis-light response curves of Q2 and Q3 treatments were increased the most. The apparent quantum efficiency, maximum net photosynthetic rate, light saturation point and dark respiration rate of Q2 and Q3 treatments were significantly higher than those of Q0 and Q1 treatments at V12, R1 and R3 stages. The light compensation point was apparently lower than that of Q0 and Q1 treatments. The maize photosynthesis-CO2 response curves of Q2 and Q3 treatments demonstrated the largest increase with the increase of CO2 concentration. The CO2 saturation point, maximum net photosynthetic rate and carboxylation efficiency of Q2 and Q3 treatments were significantly higher than those of Q0 and Q1 treatments. The CO2 compensation point was obviously lower than that of Q0 and Q1 treatments. The study provides an effective irrigation and management method for maize in semi-arid area of west Jilin Province, China. When the irrigation quota reached 170 mm, the dry matter accumulation of maize and the response of maize leaves to light and CO2 were both better. 170 mm could be used as the reference value of maize irrigation quota in western Jilin Province.

Mountain birch (Betula utilis) is the most important treeline species in alpine forests of southwestern China. In order to understand the effects of future warming on treeline birch, this study was conducted to examine the effects of experimental warming on leaf phenology, growth and gas exchange of B. utilis saplings using the open top chamber (OTC) method in a treeline ecotone of eastern Tibetan Plateau. The OTCs enhanced daily mean air temperature by 2.9 K throughout the growing season. Conversely, soil moisture within the OTCs on average declined by 3% over the experimental period. Experimental warming did not affect the timing of bud break, although treeline birch saplings growing in the OTCs manifested later leaf abscission, resulting in longer leaf life span. Artificial warming significantly accelerated the leaf and shoot growth rates of treeline birch saplings, resulting in larger leaf area and longer shoot elongation late in the growing season. Moreover, experimental warming significantly reduced the leaf fluctuating asymmetry (FA) and tended to increase specific leaf area (SLA). Moreover, elevated temperatures significantly enhanced the transpiration rate (E), stomatal conductance (g s), maximum net assimilation rate (A max), dark respiration rate (R d) and apparent quantum yield (AQY) but did not influence the light compensation point (LCP) and light saturation point (LSP) of treeline birch saplings. Taken together, our results indicated that short-term experimental warming markedly altered structural/functional leaf traits and enhanced photosynthetic capacity of treeline birch saplings; such positive responses in treeline birch would be favorable for the growth of this species under future warmer world.

In order to study the applicability of different light response models to the photoresponse curves of four species of Chamaenerion, four species of Chamaenerion collected from Serzilla were used as test materials. Four common photosynthetic models were used to fit the photosynthetic response curve of the leaves. The results show that: 1) The effect of different photosynthetic response models on photosynthetic response curve of the genus chromasia was different. The fitted value of the correction model of right angled hyperbola was closest to the measured value, the R2 was 0.998, and RE was 0.216. 2) In terms of fitting the photosynthetic parameters, the initial quantum efficiency, light compensation point and dark respiration rate were suitable for fitting with non-right angle hyperbolic model. In terms of fitting the photosynthetic parameters, the initial quantum efficiency, light compensation point and dark respiration rate were suitable for fitting with non-right angle hyperbolic model. 3) The photosynthetic characteristics of C. angustifolium subsp. circumvagum reflect the negative response to high altitude radiation. Under strong radiation, the photosynthetic rate, apparent quantum efficiency, and light saturation point are low. On the other hand, C. conspersum has a positive response to high altitude radiation. C. angustifolium and C. latifolium has a higher light compensation point and higher light saturation point, but it is also positive for high altitude radiation. The response is only a choice of light intensity at different elevations, which also explains the distribution of C. angustifolium and C. latifolium in the salmonella with a single elevation, habitat, and slope.

Influences of temperature, humidity, and CO2 concentration on the photosynthesis and respiration of three-year-oldBetula platyphylla was investigated. Light compensation point, saturation point and CO2 compensation point were also determined. The results showed that the optimal temperature of photosynthesis and dark respiration was 24 °C and 30 °C, respectively, at ambient CO2. When relative humidity was 80%,Betula platyphylla could maintain strong photosynthesis. There was no significant correlation between respiration and relative humidity. The light compensation and saturation point was 25 μmol·m−2·s−1 and 1 375 μmol·m−2·s−1, respectively. The CO2 compensation point was 180 μL·L−1. The results showed thatBetula platyphylla still had potential to assimilate CO2 when CO2 concentration was above 2 400 μL·L−1.