共查询到20条相似文献,搜索用时 15 毫秒
1.
The influence of phosphorus (P) and nitrogen (N) supply on biomass, leaf area, photon saturated photosynthetic rate (Pmax), quantum yield efficiency (α), intercellular CO2 concentration (Ci), and carboxylation efficiency (CE) was investigated in Vicia faba. The influence of P on N accumulation, biomass, and leaf area production was also investigated. An increase in P supply was consistently associated with an increase in N accumulation and N productivity in terms of biomass and leaf area production. Furthermore, P increased the photosynthetic N use efficiency (NUE) in terms of Pmax and α. An increase in P supply was also associated with an increase in CE and a decrease in Ci. Under variable daily meteorological conditions specific leaf nitrogen content (NL), specific leaf phosphorus content (PL), specific leaf area (δL), root mass fraction (Rf), Pmax, and α remained constant for a given N and P supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. δL increased with increasing N supply or with increasing NL. We tested also the hypothesis that P supply positively affects both N demand and photosynthetic NUE by influencing the upper limit of the asymptotic values for Pmax and CE, and the lower limit for Ci in response to increasing N. 相似文献
2.
Mamadou Dia Sow Vincent Segura Sylvain Chamaillard Véronique Jorge Alain Delaunay Clément Lafon-Placette Régis Fichot Patricia Faivre-Rampant Marc Villar Franck Brignolas Stéphane Maury 《Tree Genetics & Genomes》2018,14(5):78
In a context of climate change and forest decline, a better understanding of the sources of tree flexibility involved in phenotypic plasticity and adaptation is needed. These last years, the role of epigenetics in the response to environmental variations has been established in several model plants at the genotype level but little is known at the level of natural populations grown in pedoclimatic sites. Here, we focused on three French natural populations of black poplar, a key pioneer tree from watersheds, planted in common garden and subjected to controlled variations of water availability. We estimated common genetic parameters such as narrow-sense heritability (h2), phenotypic differentiation index (PST), and the overall genetic differentiation index (FST) from genome-wide SNPs to evaluate the extent of epigenetic variations. Indeed, global DNA methylation levels from individuals exposed to drought or irrigated in a common garden were used. We found that the three populations were not distinguished by their levels of DNA methylation. However, a moderate drought was associated to a significant decrease in DNA methylation in the populations. Narrow-sense heritability and PST estimates of DNA methylation were similar to those found for biomass productivity. Heritability and PST were higher when trees were subjected to drought than in control condition. Negative genetic correlations between global DNA methylation and height or biomass were detected in drought condition only. Altogether, our data highlight that global DNA methylation acts as a genetic marker of natural population differentiation under drought stress in a pedoclimatic context. 相似文献
3.
Leyre Corcuera Hervé Cochard Eustaquio Gil-Pelegrin Eduardo Notivol 《Trees - Structure and Function》2011,25(6):1033-1042
The objectives of the study were to assess the phenotypic variation in the vulnerability to water stress-induced cavitation
(estimated by P50, or the xylem water potential which causes a 50% loss of conductivity) and the trade-offs between P50 and related hydraulic traits, i.e., stem specific conductivity (K
s), slope of the vulnerability curve (slope), wood density and branch size. Variability was examined for six Pinus pinaster populations covering the latitudinal range of the species and plasticity was tested through two provenance-progeny trial
sites (xeric/mesic). As expected, the overall values of P50, K
s and branch size decreased in the xeric site. Variation in P50 and K
s among populations was mainly the result of phenotypic plasticity, while wood density was genetically controlled and not affected
by the environment. Stress conditions in the xeric site promoted a convergence in P50 and K
s as a result of the high phenotypic plasticity of the populations from mesic origins. In the mesic site, the ranking of populations
for cavitation resistance and hydraulic capacity was consistent with the geographic location of the seed source. Higher resistance
to cavitation was related to lower K
s, branch size and slope, mainly at the population level, but also as a general trend across individuals. In a warmer and drier climate, there could
be a potential selection of Pinus pinaster populations from mesic origins, which showed a great responsiveness and adjustment to drought conditions (similar or higher
P50 than the populations from dry origins), in addition to a high wood density and growth. 相似文献
4.
Debasmita Chhotaray Y. Chandrakala C. S. K. Mishra P. K. Mohapatra 《Acta Physiologiae Plantarum》2014,36(6):1501-1511
The photosynthetic and physiological performances of Oryza sativa L. (rice) were evaluated in organic and conventional rice–rice agroecosystems for 120 days after transplantation by measuring net photosynthesis (P N), transpiration (E), stomatal conductance (g s), intercellular CO2 concentration (C i), chlorophyll content (SPAD) and JIP fluorescence rise. The soil health was measured as soil bacterial and fungi density and activities of soil microbial enzymes (amylase, invertase, cellulase, protease, alkaline phosphatase and dehydrogenase). The conventionally managed fields showed lower microbial density and activity than of organic fields especially after 60 days of transplantation. The crop grown in the conventional fields has significantly low level of P N and chlorophyll, but E, g s and C i did not differ significantly till 105 days after transplantation. The JIP rise was low in conventional fields than in organic fields during 90–120 days. The efficiency and plant performance parameters (φP 0, Ψ 0, φE 0, PIφ, PI Ψ , PIABS, and PItotal) showed a rapid rate of decrease in the conventional than of organic fields. Significant positive correlation could be established between the performance and soil microbial activities, whereas the stress indicating fluorescence parameters (V J, M 0, φD 0, DI0/RC) showed significant negative correlation with the soil parameters in both the farming systems. The result showed that JIP analysis can be used as an early indicator of soil fertility and plant performance. 相似文献
5.
The mechanisms underlying heritable phenotypic divergence associated with adaptation in response to environmental stresses may involve both genetic and epigenetic variations. Several prior studies have revealed even higher levels of epigenetic variation than genetic variation. However, few population‐level studies have explored the effects of epigenetic variation on species with high levels of genetic diversity distributed across different habitats. Using AFLP and methylation‐sensitive AFLP markers, we tested the hypothesis that epigenetic variation may contribute to differences in plants occupying different habitats when genetic variation alone cannot fully explain adaptation. As a cosmopolitan invasive species, Phragmites australis (common reed) together with high genetic diversity and remarkable adaptability has been suggested as a model for responses to global change and indicators of environmental fluctuations. We found high levels of genetic and epigenetic diversity and significant genetic/epigenetic structure within each of 12 studied populations sampled from four natural habitats of P. australis. Possible adaptive epigenetic variation was suggested by significant correlations between DNA methylation‐based epigenetic differentiation and adaptive genetic divergence in populations across the habitats. Meanwhile, various AMOVAs indicated that some epigenetic differences may respond to various local habitats. A partial Mantel test was used to tease out the correlations between genetic/epigenetic variation and habitat after controlling for the correlation between genetic and epigenetic variations. We found that epigenetic diversity was affected mostly by soil nutrient availability, suggesting that at least some epigenetic differentiation occurred independently of genetic variation. We also found stronger correlations between epigenetic variation and phenotypic traits than between genetic variation and such traits. Overall, our findings indicate that genetically based differentiation correlates with heterogeneous habitats, while epigenetic variation plays an important role in ecological differentiation in natural populations of P. australis. In addition, our results suggest that when assessing global change responses of plant species, intraspecific variation needs to be considered. 相似文献
6.
Sexual dimorphisms of dioecious plants are important in controlling and maintaining sex ratios under changing climate environments. Yet, little is known about sex-specific responses to elevated CO2 with soil nitrogen (N) deposition. To investigate sex-related physiological and biochemical responses to elevated CO2 with N deposition, Populus cathayana Rehd. was employed as a model species. The cuttings were subjected to two CO2 regimes (350 and 700???mol?mol?1) with two N levels (0 and 5?g?N?m?2?year?1). Our results showed that elevated CO2 and N deposition separately increased the total number of leaves, leaf area (LA), leaf mass, net photosynthetic rate (P n), light saturated photosynthetic rate (P max), chlorophyll a (Chl a), and chlorophyll a to chlorophyll b ratio (Chl a/b) in both males and females of P. cathayana. However, the effects on LA, leaf mass, P n, P max, Chl a and Chl a/b were weakened under the combined treatment of elevated CO2 and N deposition. Males had higher leaf mass, P n, P max, apparent quantum yield (??), carboxylation efficiency (CE), Chl a, Chl a/b, leaf N, and root carbon to N ratio (C/N) than did females under elevated CO2 with N deposition. In contrast to males, females had significantly higher levels of soluble sugars in leaves and greater starch accumulation in roots and stems under the same condition. The results of the present work imply that P. cathayana females are more responsive and suffer from greater negative effects on growth and photosynthetic capacity than do males when grown under elevated CO2 with soil N deposition. 相似文献
7.
《Plant science》1988,57(1):9-17
Photosynthesis and assimilate partitioning were measured in barley (Hordeum vulgare L.) seedlings raised from seed with mineral nutrient solution containing either 0 or 1 mmolar orthophosphate (Pi). Carbon assimilation rates and leaf extension rates were inhibited about 40% by low Pi treatment. Starch and sucrose levels were similar in Pi-depleted compared to control leaves during most of the photoperiod. These results indicated that low Pi treatment inhibited carbon export from the primary leaf. Acid extractable Pi decreased about 60% in Pi-depleted barley leaves after a dark to light transition. In similar experiments with control barley and tobacco (Nicotiana tabacum L.) leaves acid extractable Pi decreased about 25% and 15%, respectively. These findings provided preliminary evidence for a diurnal variation in leaf Pi content. Photosynthetic intermediate levels were lower and extractable enzyme activities were the same or higher in low Pi compared to control leaves. These observations suggested that photosynthetic intermediate pools turnover more quickly in low Pi than in Pi-sufficient leaves. 相似文献
8.
Ebe Merilo Ingmar Tulva Olaf Räim Aveli Kükit Arne Sellin Olevi Kull 《Trees - Structure and Function》2009,23(5):951-958
Needle nitrogen partitioning and photosynthesis of Norway spruce were studied in a forest chronosequence in Järvselja Experimental Forest, Estonia. Current- and previous-year shoots were sampled from upper and lower canopy positions in four stands, ranging in age from 13 to 82 years. A/c i curves were determined to obtain maximum carboxylation rate (V cmax) and maximum rate of electron transport (J max), whereas needle nitrogen partitioning into carboxylation (P R), bioenergetics associated with electron transport (P B) and thylakoid light harvesting components (P L) was calculated from the values of V cmax, J max and leaf chlorophyll concentration. The greatest changes in studied needle characteristics took place between tree ages of 13 and 26 years, and this pattern was independent of needle age and canopy position. Needle mass per projected area (LMA) was lowest in the 13-year-old stand and mass-based nitrogen concentration (NM) was generally highest in that stand. The values of LMA were significantly higher and those of NM lower in the 26-year-old stand. Mass-based V cmax and J max were highest in the 13-year-old stand. Area-based photosynthetic capacity was independent of tree age. The proportion of photosynthetic nitrogen (P R, P B and P L) was highest and that of non-photosynthetic nitrogen lowest in the 13-year-old stand. Current-year needles had lower LMA and P L, but higher photosynthetic capacity compared to 1-year-old foliage. Needles from lower canopy positions exhibited lower LMA, area-based nitrogen concentration and photosynthetic capacity than needles from upper canopy. The period of substantial reductions in needle photosynthetic capacity and changes in nitrogen partitioning coincides with the onset of reproductive phase during tree ontogeny. 相似文献
9.
The diurnal variations of photosynthesis of three dominant species, including Glycine soja, Phragmites australis, and Cynanchum chinensis, in the Yellow River Delta in China have been studied under the same natural conditions using a Li-6400 portable photosynthesis system. The results showed that the curves of diurnal variations of net photosynthetic rate (PN) of the three plants were different. The diurnal variation of PN on C. chinensis was a midday depression pattern and had two peaks. However, PN of G. soja and P. australis showed single-peak curves. The transpiration rate (E) of G. soja was significantly higher than that of P. australis and C. chinensis, both showed single-peak curves. In general, the diurnal course of stomatal conductance (gs) followed the same pattern of PN. A similar diurnal pattern of intercellular CO2 concentration (Ci), vapor pressure deficit (VPD), and water use efficiency (WUE) was observed among different species. VPD showed single-peak curves, while WUE was characterized by double-peak curves, which was contrary to Ci. Linear correlations among photosynthetic variables and key environmental factors indicate high positive correlations between PN and E, PN and photosynthetic active radiation, PN and leaf temperature (Tleaf), PN and VPD, and between PN and gs except C. chinensis. Negative correlations among PN and relative humidity, PN and Ci were found. The irradiance response curves derived from the leaves were substantially affected by different species. C. chinensis showed highest apparent quantum efficiency, followed by P. australis and G. soja, while apparent dark respiration (Rd), convexity (k), light saturation point, and maximum gross CO2 assimilation rate (Pmax) of G. soja were higher than those of P. australis and C. chinensis. The irradiance response curve of PN and WUE of different plant species followed the same order: G. soja>C. chinensis>P. australis. They were both higher than most of other species. It was concluded that plant species adapting to the saline–alkaline habitat showed higher photosynthesis. In addition, G. soja is also effective to improve saline–alkaline soil quality. 相似文献
10.
To investigate the effects of glucohexaose (P6) on cucumber, leaf CO2 assimilation, chlorophyll fluorescence parameters, chlorophyll content, and carbohydrate metabolism were examined in cucumber plants. The net photosynthetic rate (P n ) of cucumber leaves was enhanced after being treated with 10 μg mL?1 P6. The increase was correlated with increases in transpiration rate (E) and stomatal conductance (G s), whereas the intercellular CO2 concentration (C i) was not different from the control plants. Chlorophyll content, absorption of light energy per unit area (ABS/CS), capture of light energy per unit area (TRo/CS), quantum yield of electron transport per unit area (ETo/CS), maximum photochemical efficiency of PSII (φP o), quantum yield of photosynthetic institution electron transfer (φE o), probability of other electron acceptors that captured exciton-transferred electrons to the electronic chain which exceeds QA (ψ o), number of reaction centers per unit leaf area (RC/CSo), and the performance index on absorption basis (PIABS) were improved, but heat dissipation per unit area (DIo/CS) and maximum quantum yield of non-chemical quenching (φD o) were reduced. In addition, increases in sucrose, soluble sugars, and starch contents were observed in P6-treated plants. However, H2O2 scavenger (DMTU) or NADPH oxidase inhibitor (DPI) pretreatment significantly abolished the effect of P6 on photosynthesis. The results demonstrated that ROS played a critical role in P6-induced photosynthesis. The increase in chlorophyll content together with efficient light absorption, transmission, and conversion in P6-treated plants is important for increasing photosynthesis. 相似文献
11.
12.
Lisa Adolfsson Katalin Solymosi Mats X. Andersson áron Keresztes Johan Uddling Beno?t Schoefs Cornelia Spetea 《PloS one》2015,10(1)
Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with Pi fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with Pi fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased Pi supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and Pi-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by Pi fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and Pi-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area. 相似文献
13.
滨海湿地生态系统具有较高的初级生产力,是地球生态系统主要的碳库之一。然而,气候变暖和外来物种入侵通过改变植物光合特征性能使这一碳库的稳定性存在诸多的不确定性。利用在江苏盐城芦苇湿地和互花米草湿地建设的两个增温观测站,采用便携式光合荧光测量系统研究了本土植物芦苇(Phragmites australis)和入侵物种互花米草(Spartina alterniflora)光合特性对模拟增温的响应特征和机制。光合作用日调查变化曲线显示,增温使芦苇的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)都发生了显著的下降,但互花米草的各同名参数却表现出相反的变化特征,表明增温使互花米草的生理机能增强,促进了光合作用;根据Pn和胞间CO2浓度(Ci)的变化趋势推断互花米草和芦苇光合速率变化均为非气孔限制因素驱动。利用直角双曲线修正模型拟合的光响应曲线结果显示,芦苇增温组的光响应曲线位于对照组下方,互花米草增温组的光响应曲线位于对照组上方;增温降低了所研究植物的光补偿点(LCP),表明增温可提高两种植物利用弱光的能力;增温增加了互花米草光补偿点(LCP)和光饱和点(LSP)间值域范围,从而揭示了增温可有效提高互花米草利用光合有效辐射的能力;增温降低了芦苇的暗呼吸速率(Rd),芦苇受到增温的胁迫,在减缓新陈代谢的同时也减弱了光合作用,而互花米草表现出相反特征。由此推测增温条件下入侵植物互花米草同化大气CO2的能力(即碳汇能力)优于本土植物芦苇,这也是互花米草成为入侵物种的主要原因之一。 相似文献
14.
Chrococcoid cyanobacteria of the genus Synechococcus are the important component of marine and freshwater ecosystems. Picocyanobacteria comprise even 80% of total cyanobacterial biomass and contribute to 50% of total primary cyanobacterial bloom production. Chlorophyll (Chl) fluorescence and photosynthetic light response (P-I) curves are commonly used to characterize photoacclimation of Synechococcus strains. Three brackish, picocyanobacterial strains of Synechococcus (BA-132, BA-124, BA-120) were studied. They were grown under 4 irradiances [10, 55, 100, and 145 μmol(photon) m?2 s?1] and at 3 temperatures (15, 22.5, and 30°C). Photosynthetic rate was measured by Clark oxygen electrode, whereas the Chl fluorescence was measured using Pulse Amplitude Modulation fluorometer. Based on P-I, two mechanisms of photoacclimation were recognized in Synechococcus. The maximum value of maximum rate of photosynthesis (P max) expressed per biomass unit at 10 μmol(photon) m?2 s?1 indicated a change in the number of photosynthetic units (PSU). The constant values of initial slope of photosynthetic light response curve (α) and the maximum value of P max expressed per Chl unit at 145 μmol(photon) m?2 s?1 indicated another mechanism, i.e. a change in PSU size. These two mechanisms caused changes in photosynthetic rate and its parameters (compensation point, α, saturation irradiance, dark respiration, P max) upon the influence of different irradiance and temperature. High irradiance had a negative effect on fluorescence parameters, such as the maximum quantum yield and effective quantum yield of PSII photochemistry (φPSII), but it was higher in case of φPSII. 相似文献
15.
The source-sink relationship is one of major determinants of plant performance. The influence of reproductive sink demand on light-saturated photosynthesis (Pmax), dark respiration (RD), stomatal conductance (gs), intrinsic water-use efficiency (WUEi), contents of soluble sugar (SSC), nitrogen, carbon, and photosynthetic pigments was examined in blueberry (Vaccinium corymbosum L. cv. ‘Brigitta’) during the final stage of rapid fruit growth. Measurements were performed three times per day on developed, sun-exposed leaves of girdled shoots with 0.1, 1, and 10 fruit per leaf (0.1F:L, 1F:L, and 10F:L, respectively) and nongirdled shoots bearing one fruit per leaf (NG). Girdling and lower fruit amount induced lower Pmax, gs, N, and total chlorophyll (Chl) and higher WUEi, SSC, RD, Chl a/b ratio and carotenoids-to-chlorophylls ratio (Car/Chl) for the 1F:L and 0.1F:L treatments. The impact of girdling was counterbalanced by 10F:L, with NG and 10F:L having similar values. Variables other than Pmax, RD, gs, WUEi, and SSC were unaffected throughout the course of the day. Pmax and gs decreased during the course of the day, but gs decreased more than Pmax in the afternoon, while WUEi was increasing in almost all treatments. SSC increased from the morning until afternoon, whereas RD peaked at noon regardless of the treatment. Generally, Pmax was closely and negatively correlated to SSC, indicating that sugar-sensing mechanisms played an important role in regulation of blueberry leaf photosynthesis. With respect to treatments, Pmax and N content were positively related, while RD was not associated to substrate availability. The enhanced Car/Chl ratio showed a higher photoprotection under the lower sink demand. Changes in the source-sink relationship in ‘Brigitta’ blueberry led to a rearrangement of physiological and structural leaf traits which allowed adjusting the daily balance between carbon assimilation and absorbed light energy. 相似文献
16.
The influence of phosphorus (P) and nitrogen (N) supply on biomass, leaf area, photon saturated photosynthetic rate (Pmax), quantum yield efficiency (), intercellular CO2 concentration (Ci), and carboxylation efficiency (CE) was investigated in Vicia faba. The influence of P on N accumulation, biomass, and leaf area production was also investigated. An increase in P supply was consistently associated with an increase in N accumulation and N productivity in terms of biomass and leaf area production. Furthermore, P increased the photosynthetic N use efficiency (NUE) in terms of Pmax and . An increase in P supply was also associated with an increase in CE and a decrease in Ci. Under variable daily meteorological conditions specific leaf nitrogen content (NL), specific leaf phosphorus content (PL), specific leaf area (L), root mass fraction (Rf), Pmax, and remained constant for a given N and P supply. A monotonic decline in the steady-state value of Rf occurred with increasing N supply. L increased with increasing N supply or with increasing NL. We tested also the hypothesis that P supply positively affects both N demand and photosynthetic NUE by influencing the upper limit of the asymptotic values for Pmax and CE, and the lower limit for Ci in response to increasing N.This revised version was published online in March 2005 with corrections to the page numbers. 相似文献
17.
Different photosynthetic responses to night chilling among twelve populations of Jatropha curcas 总被引:1,自引:0,他引:1
Jatropha curcas, one of the most important energy plant resources, is vulnerable to chilling. To evaluate the effects of chilling on photosynthesis of J. curcas and intraspecific differences in chilling tolerance, seedlings of twelve populations were treated with the temperature of 4–6°C for five consecutive nights with normal environmental temperature during the day. Night chilling treatment decreased light-saturated photosynthetic rate (P max) significantly for all populations. Stomatal limitation could not explain the decreased P max because intracellular CO2 concentration was not significantly reduced by night chilling in all populations (with only one exception). The decreased soluble-protein content, which may be related to the increased malondialdehyde (MDA) content, contributed to the decreased P max. The increased MDA content indicated that oxidative stress occurred after night chilling, which was associated with the larger decrease in P max compared with the decrease in actual photochemical efficiency of photosystem II, and the slight increase in thermal dissipation of excessive energy. After five-day recovery, MDA (with two exceptions) and P max still did not recover to the levels as those before night chilling treatment for all populations, indicating that J. curcas was vulnerable to chilling. Chilling tolerance was significantly different among populations. Populations originating from high elevations had greater chilling-tolerant abilities than populations originating from low elevations, showing a local adaptation to environmental temperatures of origins. Our study shed light on the possibility to find or breed chilling-tolerant genotypes of J. curcas. 相似文献
18.
Leaf mass per unit area (LMA), carbon and nitrogen contents, leaf construction cost, and photosynthetic capacity (P
max) of Adiantum reniforme var. sinensis, an endangered fern endemic to the Three Gorges region in southwest China, were compared in five populations differing in
habitat such as soil moisture and irradiance. The low soil moisture and high irradiance habitat population exhibited significantly
higher LMA, area-based leaf construction (CCA), and carbon content (CA), but lower leaf nitrogen content per unit dry mass (NM) than the other habitat populations. The high soil moisture and low irradiance habitat populations had the lowest CCA, but their cost/benefic ratios of CCA/P
max were similar to the medium soil moisture and irradiance habitat population due to their lower leaf P
max. Hence A. reniforme var. sinensis prefers partially shaded, moist but well-drained, slope habitats. Due to human activities, however, its main habitats now
are cliffs or steeply sloped bare rocks with poor and thin soil. The relatively high energy requirements and low photosynthetic
capacity in these habitats could limit the capability of the species in extending population or interspecific competition
and hence increase its endangerment. 相似文献
19.
C.F. Musil J.L. Arnolds P.D.R. van Heerden B.S. Kgope 《Environmental and Experimental Botany》2009,66(1):38-45
European annual grasses are displacing native species along South Africa's West Coast, a region rich in wildflower diversity which forms the basis of a growing nature-based tourist industry. Little is known of the physiological and biochemical mechanisms underlying competitive interactions between these grasses and native taxa and how they are affected by resource supply. Consequently, this study compared Photosystem II function, photosynthetic pigment concentrations, gas and water exchange rates, Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) contents, flowering and biomass accumulation in a native geophyte Tritonia crocata (L.) Ker. Gawl. grown in monoculture and admixed with an alien grass Lolium multiflorum Lam at different levels of nutrient and water supply. Diminished stomatal conductances were the primary cause of reduced net CO2 assimilation rates and consequent decreased biomass accumulation in T. crocata admixed with L. multiflorum at all levels of water and nutrient supply with one exception. These corresponded with decreased soil water contents induced presumably by more efficient competition for water by L. multiflorum whose biomass was inversely correlated with soil water content. At low levels of water and nutrient supply, both stomatal and metabolic impairments to photosynthesis were apparent in T. crocata admixed with L. multiflorum. The metabolic impairments included a decline in the efficiency of primary photochemistry (trapping) (φP0/1 ? φP0), associated with a decrease in leaf chlorophyll a and b content, a decreased efficiency of conversion of excitation energy to electron transport (Ψ0/1 ? Ψ0) pointing to a reduction in electron transport capacity beyond QA? and a decline in apparent Rubisco activity (Vc,max) and Rubisco content. Under conditions of low nutrient and high water supply, only metabolic impairments to photosynthesis (decreased RC/ABS, chlorophyll a and Rubisco content) were apparent in T. crocata admixed with L. multiflorum. These impairments resulted in a down regulation of photosynthesis and a reallocation of fixed carbohydrate reserves to floral production which increased significantly in T. crocata under these conditions only and corresponded with a decline in the mass of its underground storage organ. 相似文献
20.
Gas exchanges and related leaf traits of three co-occurring species of genus Cypripedium (C. yunnanense Franch., C. guttatum SW., and C. flavum P.F. Hunt et Summerch.) were investigated in a scrubland at 3 460 m a.s.l. in the Hengduan Mountains. The considered species had similar
photosynthetic responses to photosynthetic photon flux density (PPFD) and air temperature. The photosynthetic capacity (P
max), carboxylation efficiency (CE), apparent quantum efficiency (AQE), PPFD-saturated rate of electron transport (Jmax), respiration rate (R
D), and leaf nitrogen content per unit area (LNC) of C. guttatum were higher than those of C. yunnanense and C. flavum. The highest P
max of C. guttatum was related to the highest LNC and the lowest ratio of intercellular CO2 concentration to atmospheric CO2 concentration (C
i/C
a). However, no significant differences in stomatal conductance (g
s) and relative stomatal limitations (RSL) were observed among the three species. Hence biochemical limitation had a dominant
role in P
max differences among the considered species. 相似文献