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1.
In sunflower (Helianthus annuus L.) grown under controlled conditions and subjected to drought by withholding watering, net photosynthetic rate (P
N) and stomatal conductance (g
s) of attached leaves decreased as leaf water potential (Ψw) declined from −0.3 to −2.9 MPa. Although g
s decreased over the whole range of Ψw, nearly constant values in the intercellular CO2 concentrations (C
i) were observed as Ψw decreased to −1.8 MPa, but C
i increased as Ψw decreased further. Relative quantum yield, photochemical quenching, and the apparent quantum yield of photosynthesis decreased
with water deficit, whereas non-photochemical quenching (qNP) increased progressively. A highly significant negative relationship between qNP and ATP content was observed. Water deficit did not alter the pyridine nucleotide concentration but decreased ATP content
suggesting metabolic impairment. At a photon flux density of 550 μmol m−2 s−1, the allocation of electrons from photosystem (PS) 2 to O2 reduction was increased by 51 %, while the allocation to CO2 assimilation was diminished by 32 %, as Ψw declined from −0.3 to −2.9 MPa. A significant linear relationship between mean P
N and the rate of total linear electron transport was observed in well watered plants, the correlation becoming curvilinear
when water deficit increased. The maximum quantum yield of PS2 was not affected by water deficit, whereas qP declined only at very severe stress and the excess photon energy was dissipated by increasing qNP indicating that a greater proportion of the energy was thermally dissipated. This accounted for the apparent down-regulation
of PS2 and supported the protective role of qNP against photoinhibition in sunflower. 相似文献
2.
Net photosynthetic rate (P
N), stomatal conductance (g
s), intercellular CO2 concentration (C
i), transpiration rate (E), water use efficiency (WUE), and stomatal limitation (Ls) of Populus euphratica grown at different groundwater depths in the arid region were measured. g
s of the trees with groundwater depth at 4.74 m (D4) and 5.82 m (D5) were lower and a little higher than that at 3.82 m (D3), respectively. Compared with C
i and Ls of the D3 trees, C
i decreased and Ls increased at 4.74 m, however, Ci increased and Ls decreased at D5. Hence photosynthetic reduction of P. euphratica was attributed to either stomatal closure or non-stomatal factors depending on the groundwater depths in the plant locations.
P
N of the D3 trees was significantly higher than those at D4 or D5. The trees of D4 and D5 did not show a significant difference in their P
N, indicating that there are mechanisms of P. euphratica tolerance to mild and moderate drought stress. 相似文献
3.
Cuttings of P. przewalski were exposed to two different watering regimes which were watered to 100 and 25 % of field capacity (WW and WS, respectively).
Drought stress not only significantly decreased net photosynthetic rate (P
N), transpiration rate (E), stomatal conductance (g
s), efficiency of photosystem 2 (PS2) (Fv/Fm and yield), and increased intrinsic water use efficiency (WUEi) under controlled optimal conditions, but also altered the diurnal changes of gas exchange, chlorophyll fluorescence, and
WUEi. On the other hand, WS also affected the P
N-photosynthetically active radiation (PAR) response curve. Under drought stress, P
N peak appeared earlier (at about 10:30 of local time) than under WW condition (at about 12:30). At midday, there was a depression
in P
N for WS plants, but not for WW plants, and it could be caused by the whole microclimate, especially high temperature, low
relative humidity, and high PAR. There were stomatal and non-stomatal limitations to photosynthesis. Stomatal limitation dominated
in the morning, and low P
N at midday was caused by both stomatal and non-stomatal limitations, whereas non-stomatal limitation dominated in the afternoon.
In addition, drought stress also increased compensation irradiance and dark respiration rate, and decreased saturation irradiance
and maximum net photosynthetic rate. Thus drought stress decreased plant assimilation and increased dissimilation through
affected gas exchange, the diurnal pattern of gas exchange, and photosynthesis-PAR response curve, thereby reducing plant
growth and productivity. 相似文献
4.
The net photosynthetic rate (P
N), intercellular CO2 concentration (C
i), stomatal conductance (g
s), transpiration rate (E), water use efficiency (WUE), and leaf biomass production of four American flue-cured tobacco (Nicotiana tabacum L.) cultivars K 326, K 358, and Speight G 28 were compared with three local Indian cultivars 16/103, Special FCV, and PCT-7, during 1994 and 1995 crop seasons under irrigated and rainfed production systems (Northern light soils, NLS, and Karnataka light soils, KLS) in India. By comparison, the American tobacco cv. K 326 showed the highest P
N and g
s. A positive correlation was found between P
N and biomass production in all the varieties tested (r = 0.55 in NLS and 0.73 in KLS). The American cultivars were superior than the local cultivars in their biomass production and P
N under Indian farming conditions. 相似文献
5.
At the grain-filling stage, net photosynthetic rate (P
N), stomatal conductance (g
s), and ribulose-1,5-bisphosphate carboxylation efficiency (CE) were correlated in order to find the determinant of photosynthetic capacity in rice leaves. For a flag leaf, P
N in leaf middle region was higher than in its upper region, and leaf basal region had the lowest P
N value. The differences in g
s and CE were similar. P
N, g
s, and CE gradually declined from upper to basal leaves, showing a leaf position gradient. The correlation coefficient between P
N and CE was much higher than that between P
N and g
s in both cases, and P
N was negatively correlated with intercellular CO2 concentration (C
i). Hence the carboxylation activity or activated amount of ribulose-1,5-bisphosphate carboxylase/oxygenase rather than gs was the determinant of the photosynthetic capacity in rice leaves. In addition, in flag leaves of different tillers P
N was positively correlated with g
s, but negatively correlated with C
i. Thus g
s is not the determinant of the photosynthetic capacity in rice leaves.The study was supported by the State Key Basic Research and Development Plan (No.G1998010100). 相似文献
6.
采煤塌陷影响下土壤含水量变化对柠条气孔导度、蒸腾与光合作用速率的影响 总被引:2,自引:0,他引:2
采煤塌陷引起的土壤环境因子的变化对矿区植物生长的影响越来越受到人们的关注,气孔导度、蒸腾与光合作用作为环境变化响应的敏感因子,研究植物气孔导度、蒸腾与光合作用的变化是揭示荒漠矿区自然环境变化及其规律的重要手段之一。研究采煤塌陷条件下植物光合生理的变化是探究煤炭开采对植物叶片水分蒸腾散失和CO_2同化速率影响的关键环节,是探讨采煤塌陷影响下植物能量与水分交换动态的基础,而采煤矿区植物叶片气孔导度、蒸腾与光合作用速率对采煤塌陷影响下土壤含水量变化的响应如何尚不清楚。选取神东煤田大柳塔矿区52302工作面为实验场地,以生态修复物种柠条为研究对象,对采煤塌陷区和对照区柠条叶片气孔导度、蒸腾和光合作用速率以及土壤体积含水量进行监测,分析了采煤塌陷条件下土壤含水量的变化以及其对柠条叶片气孔导度、蒸腾与光合作用速率的影响。结果显示:(1)煤炭井工开采在地表形成大量裂缝,破坏了土体结构,潜水位埋深降低,土壤含水量均低于沉陷初期,相对于对照区,硬梁和风沙塌陷区土壤含水量分别降低了18.61%、21.12%;(2)柠条叶片气孔导度、蒸腾和光合作用速率均与土壤含水量呈正相关关系;煤炭开采沉陷增加了地表水分散失,加剧了土壤水分胁迫程度,为了减少蒸腾导致的水分散失,柠条叶片气孔阻力增加,从而气孔导度降低,阻碍了光合作用CO_2的供应,从而导致柠条叶片光合作用速率的降低,蒸腾速率也显著降低。 相似文献
7.
M. D. Fernandez 《Photosynthetica》2006,44(1):32-38
In the seasonally flooded forest of the Mapire River, a tributary of the Orinoco, seedlings remain totally covered by flood
water for over six months. In order to characterize the physiological response to flooding and submergence, seedlings of the
tree Pouteria orinocoensis, an important component of the forest vegetation, were subjected experimentally to flooding. Flooding was imposed gradually,
the maximum level of flood including submerged and emerged leaves. After 45 d a severe reduction of net photosynthetic rate
(P
N) and stomatal conductance (g
s) was observed in emerged leaves, whereas leaf water potential remained constant. The decrease in P
N of emerged leaves was associated to an increase in both relative stomatal and non-stomatal limitations, and the maintenance
of the internal/air CO2 concentration (C
i/C
a) for at least 20 d of flooding. After this time, both P
N and g
s became almost zero. The decrease in photosynthetic capacity of emerged leaves with flooding was also evidenced by a decrease
in carboxylation efficiency; photon-saturated photosynthetic rate, and apparent quantum yield of CO2 fixation. Oxygen evolution rate of submerged leaves measured after three days of treatment was 7 % of the photosynthetic
rate of emerged leaves. Submersion determined a chronic photoinhibition of leaves, viewed as a reduction in maximum quantum
yield in dark-adapted leaves, whereas the chlorophyll fluorescence analysis of emerged leaves pointed out at the occurrence
of dynamic, rather than chronic, photoinhibition. This was evidenced by the absence of photochemical damage, i.e. the maintenance of maximum quantum yield in dark-adapted leaves. Nevertheless, the observed lack of complementarity between
photochemical and non-photochemical quenching after 12 d of flooding implies that the capacity for photochemical quenching
decreased in a non-co-ordinate manner with the increase in non-photochemical quenching. 相似文献
8.
Photosynthesis and Chlorophyll Fluorescence in Two Hybrids of Sorghum under Different Nitrogen and Water Regimes 总被引:14,自引:0,他引:14
In two hybrids of sorghum (Sorghum bicolor Moench.), C51 and C42, high nitrogen concentration (HN) increased net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) of well watered (HW) plants. Water stressing (LW plants) resulted in low PN, gs, and E in both hybrids, but the values were still higher in HN plants as compared to low nitrogen-grown (LN) plants. Intercellular CO2 concentration (Ci) increased in droughted plants. This increase was much higher in LN plants as compared to HN plants. Instantaneous water use efficiency was lower in LN plants as a consequence of a greater effect of water stress on photosynthesis. Leaf water potential was reduced by water stress in all treatments. Analysis of chlorophyll a fluorescence at room temperature showed that photosystem 2 (PS2) was rather tolerant to the water stress imposed. Water stress caused a slight decrease in the efficiency of excitation capture by open PS2 reaction centres (Fv/Fm). The in vivo quantum yield of PS2 photochemistry (PS2) and the photochemical quenching coefficient (qP) were slightly reduced, while the nonphotochemical quenching coefficient (qN) was increased under the water stress. However, in hybrid C42 these characters were little or not affected by the water stress. 相似文献
9.
J. Moutinho-Pereira N. Magalhães B. Gonçalves E. Bacelar M. Brito C. Correia 《Photosynthetica》2007,45(2):202-207
Optical characteristics, contents of photosynthetic pigments, total soluble sugars, and starch, rates of gas exchange, chlorophyll (Chl) a fluorescence, and leaf water relations were analysed in three Vitis vinifera L. cultivars, Tinto Cão (TC), Touriga Nacional (TN), and Tinta Roriz (TR), grown in Mediterranean climate. Chl content was significantly lower in TC than in TN and TR leaves, while the Chl a/b ratio was higher. TR had the lowest net photosynthetic rate, stomatal conductance, and contents of soluble sugars and starch than TN and TC. In spite of low Chl content, TC showed the lowest photon absorbance and the highest photochemical efficiency of photosystem 2. TC had the lowest predawn and midday leaf water potential. The capability for osmotic adjustment was similar among cultivars and the calculated modulus of elasticity was higher in TC leaves. The typical lighter green leaves of TC seemed to be an adaptive strategy to high irradiance and air temperature associated to water stress. 相似文献
10.
Influence of manganese (Mn) toxicity on photosynthesis in ricebean (Vigna umbellata) was studied by the measurement of gas exchange characteristics and chlorophyll fluorescence parameters. The net photosynthetic
rate (P
N), transpiration rate (E), and stomatal conductance (g
s) were reduced with increasing Mn concentration in nutrient solution. The reduction in g
s and E was more pronounced at 6 d of Mn treatment. However, P
N declined at 2 d of Mn treatment implying that the reduction in photosynthesis was not due to the direct effect of Mn on stomatal
regulation. Mn did not affect the maximum efficiency of photosystem 2 (PS2) photochemistry (Fv/Fm). A reduction in photochemical quenching (qP) and excitation capture efficiency of open PS2 (Fv′/Fm′) with a concomitant increase in qN was observed. This implies that reduced demand for ATP and NADPH due to the reduction in photosynthesis causes a down-regulation
of PS2 photochemistry and thus a high pH gradient (increase in qN) and limited electron transport (decreased qP).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
Photosynthetic and stomatal responses of two tropical and two temperate trees to atmospheric humidity 总被引:4,自引:0,他引:4
The effects of leaf to air vapour pressure differences (ΔW) on net photosynthetic rate (PN) and stomatal conductance (gs) were examined in the leaves of two tropical rain forest trees, Eugenia grandis and Pongamia pinnata, and two temperate evergreen
trees, Viburnum awabuki and Daphniphyllum macropodum. A single leaf was set inside a small chamber and ΔW was varied from
7 to 24 mmol mol-1 at 25 and 500 μmol m-2 s-1 of photon flux density. PN and gs of the two tropical rain forest trees decreased with increasing ΔW, while the two temperate evergreen trees were not highly
responsive to ΔW. P. pinnata was more sensitive to ΔW in its stomatal response, and had a higher stomatal density and higher
stomatal index than did the two temperate trees and another tropical tree. Significant reductions i n gs and intercellular CO2 concentrations in the two tropical trees at high ΔW suggest that the decline of PN was due to the decrease in gs. The responses of PN and gs indicated that the tropical trees were more sensitive to ΔW than were the temperate ones.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
12.
Plants of Podophyllum hexandrum, collected from lower, mid, and upper distribution limits in alpine Himalaya were studied under greenhouse conditions to
evaluate the photosynthetic response. Net photosynthetic rates (P
N), stomatal conductance (g
s), and efficiency of carbon uptake increased with altitude. The maximum P
N and g
s were measured in the considered population during the 3–6th week of development. P
N and g
s decreased on an average by 58 and 48 % from maximum rates reached around 4th week to the 10th week of growth, respectively. The photosynthetic response in the three ecotypes appeared to be genetically controlled. 相似文献
13.
K. Palanisamy 《Photosynthetica》1999,36(4):635-638
Response of net photosynthetic rate (P
N), stomatal conductance (g
s), intercellular CO2 concentration (c
i), and photosynthetic efficiency (Fv/Fm) of photosystem 2 (PS2) was assessed in Eucalyptus cladocalyx grown for long duration at 800 (C800) or 380 (C380) μmol mol-1 CO2 concentration under sufficient water supply or under water stress. The well-watered plants at C800 showed a 2.2 fold enhancement of P
N without any change in g
s. Under both C800 and C380, water stress decreased P
N and g
s significantly without any substantial reduction of c
i, suggesting that both stomatal and non-stomatal factors regulated P
N. However, the photosynthetic efficiency of PS2 was not altered.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
Independent short-term effects of photosynthetic photon flux density (PPFD) of 50–400 μmol m−2 s−1, external CO2 concentration (C
a) of 85–850 cm3 m−3, and vapor pressure deficit (VPD) of 0.9–2.2 kPa on net photosynthetic rate (P
N), stomatal conductance (g
s), leaf internal CO2 concentration (C
i), and transpiration rates (E) were investigated in three cacao genotypes. In all these genotypes, increasing PPFD from 50 to 400 μmol m−2 s−1 increased P
N by about 50 %, but further increases in PPFD up to 1 500 μmol m−2 s−1 had no effect on P
N. Increasing C
a significantly increased P
N and C
i while g
s and E decreased more strongly than in most trees that have been studied. In all genotypes, increasing VPD reduced P
N, but the slight decrease in g
s and the slight increase in C
i with increasing VPD were non-significant. Increasing VPD significantly increased E and this may have caused the reduction in P
N. The unusually small response of g
s to VPD could limit the ability of cacao to grow where VPD is high. There were no significant differences in gas exchange
characteristics (g
s, C
i, E) among the three cacao genotypes under any measurement conditions. 相似文献
15.
Influence of drought (D) on changes of leaf water potential (Ψ) and parameters of gas exchange in D-resistant and D-sensitive
genotypes of triticale and maize was compared. Soil D (from −0.01 to −2.45 MPa) was simulated by mannitol solutions. At −0.013
MPa significant differences in Ψ, net photosynthetic rate (P
N), transpiration rate (E), stomatal conductance (g
s), and internal CO2 concentration (C
i) of D-resistant and D-sensitive triticale and maize genotypes were not found. Together with the increase in concentration
of the mannitol solution the impact of D on E and g
s for D-sensitive genotypes (CHD-12, Ankora) became lower than for the D-resistant ones (CHD-247, Tina). Inversely, impact
of D on Ψ was higher in D-sensitive than D-resistant genotypes. From 1 to 3 d of D, a higher decrease in P
N was observed in D-resistant genotypes than in the D-sensitive ones. Under prolonged D (5–14 d) and simultaneous more severe
D the decrease in P
N was lower in D-resistant than in D-sensitive genotypes. Changes in Ψ, P
N, E, and g
s caused by D in genotypes differing in the drought susceptibility were similar for triticale and maize. Compared to control
plants, increase of C
i was different for triticale and maize genotypes. Hence one of the physiological reasons of different susceptibility to D
between sensitive and resistant genotypes is more efficient protection of tissue water status in resistant genotypes reflected
in higher decrease in g
s and limiting E compared to the sensitive ones. Other reason, observed in D-resistant genotypes during the recovery from D-stress, was more
efficient removal of detrimental effects of D. 相似文献
16.
Two cultivars (Katy and Erhuacao) of apricot (Prunus armeniaca L.) were evaluated under open-field and solar-heated greenhouse conditions in northwest China, to determine the effect of
photosynthetic photon flux density (PPFD), leaf temperature, and CO2 concentration on the net photosynthetic rate (P
N). In greenhouse, Katy registered 28.3 μmol m−2 s−1 for compensation irradiance and 823 μmol m−2 s−1 for saturation irradiance, which were 73 and 117 % of those required by Erhuacao, respectively. The optimum temperatures
for cvs. Katy and Erhuacao were 25 and 35 °C in open-field and 22 and 30 °C in greenhouse, respectively. At optimal temperatures,
P
N of the field-grown Katy was 16.5 μmol m−2 s−1, 21 % less than for a greenhouse-grown apricot. Both cultivars responded positively to CO2 concentrations below the CO2 saturation concentration, whereas Katy exhibited greater P
N (18 %) and higher carboxylation efficiency (91 %) than Erhuacao at optimal CO2 concentration. Both cultivars exhibited greater photosynthesis in solar-heated greenhouses than in open-field, but Katy performed
better than Erhuacao under greenhouse conditions. 相似文献
17.
A positive linear relationship between the net CO2 exchange rate (P
N) and the leaf stomatal conductance (gs) under an optimal temperature, and even more distinct one after a short-term chilling (CH, 15-17 h, 2 °C in darkness), that
was found in two tomato cultivars (sensitive to a low temperature cv. Robin and tolerant cv. New Yorker) suggested a partial
stomatal limitation of photosynthesis. The CH treatment of cv. Robin resulted in an intercellular CO2 concentration (C
i) increase because of which a negative correlation between C
i and P
N was observed. In cv. New Yorker a positive correlation was observed. Detrimental effect of the low temperature in cv. Robin
was more evident in plants with a relatively small root system (SR), but drought-hardening positively affected the response
to CH only in the plants with bigger roots (BR). On the contrary, in cv. New Yorker the favourable effect of such pre-treatment
was more evident in SR than in BR plants.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
Water-water cycle involved in dissipation of excess photon energy in phosphorus deficient rice leaves 总被引:2,自引:2,他引:0
The water-water cycle which may be helpful for dissipating the excitation pressure over electron transport chain and minimizing
the risk of photoinhibition and photodamage was investigated in rice after 10-d P-deficient treatment. Net photosynthetic
rate decreased under P-deficiency, thus the absorption of photon energy exceeded the energy required for CO2 assimilation. A more sensitive response of effective quantum yield of photosystem 2 (ΦPS2) to O2 concentration was observed in plants that suffered P starvation, indicating that more electrons were transported to O2 in the P-deficient leaves. The electron transport rate through photosystem 2 (PS 2) (Jf) was stable, and the fraction of electron transport rate required to sustain CO2 assimilation and photorespiration (Jg/Jf) was significantly decreased accompanied by an increase in the alternative electron transport (Ja/Jf), indicating that a considerable electron amount had been transported to O2 during the water-water cycle in the P-deficient leaves. However, the fraction of electron transport to photorespiration (Jo/Jf) was also increased in the P-deficient leaves and it was less sensitive than that of water-water cycle. Therefore, water-water
cycle could serve as an efficient electron sink. The higher non-photochemical fluorescence quenching (qN) in the P-deficient leaves depended on O2 concentration, suggesting that the water-water cycle might also contribute to non-radiative energy dissipation. Hence, the
enhanced activity of the water-water cycle is important for protecting photosynthetic apparatus under P-deficiency in rice. 相似文献
19.
Two-month-old seedlings of Sophora davidii were subjected to a randomized complete block design with three water (80, 40, and 20 % of water field capacity, i.e. FC80, FC40, and FC20) and three N supply [N0: 0, Nl: 92 and Nh: 184 mg(N) kg−1(soil)] regimes. Water stress produced decreased leaf area (LA) and photosynthetic pigment contents, inhibited photosynthetic
efficiency, and induced photodamage in photosystem 2 (PS2), but increased specific leaf area (SLA). The decreased net photosynthetic
rate (P
N) under medium water stress (FC40) compared to control (FC80) might result from stomatal limitations, but the decreased P
N under severe water deficit (FC20) might be attributed to non-stomatal limitations. On the other hand, N supply could improve photosynthetic capacity by increasing
LA and photosynthetic pigment contents, and enhancing photosynthetic efficiency under water deficit. Moreover, N supply did
a little in alleviating photodamages to PS2 caused by water stress. Hence water stress was the primary limitation in photosynthetic
processes of S. davidii seedlings, while the photosynthetic characters of seedlings exhibited positive responses to N supply. Appropriate N supply
is recommended to improve photosynthetic efficiency and alleviate photodamage under water stress. 相似文献
20.
Effects of foliar application of nitrogen on the photosynthetic performance and growth of two fescue cultivars under heat stress 总被引:1,自引:0,他引:1
The effects of nitrogen fertilization on the growth, photosynthetic pigment contents, gas exchange, and chlorophyll (Chl)
fluorescence parameters in two tall fescue cultivars (Festuca arundinacea cv. Barlexas and Crossfire II) were investigated under heat stress at 38/30 °C (day/night) for two weeks. Shoot growth rate
of two tall fescue cultivars declined significantly under heat stress, and N supply can improved the growth rates, especially
for the Barlexas. Chl content, leaf net photosynthetic rate, stomatal conductance, water use efficiency, and the maximal efficiency
of photosystem 2 photochemistry (Fv/Fm) also decreased less under heat stress by N supply, especially in Crossfire II. Moreover, cultivar variations in photosynthetic
performance were associated with their different response to heat stress and nitrogen fertilization, which were evidenced
by shoot growth rate and photosynthetic pigment contents. 相似文献