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1.
The interactive effects of light intensity and controlled-release nitrogen fertilizer (CRNF) supply on growth, gas exchange,
and chlorophyll (Chl) fluorescence parameters of two species of potted Hosta seedlings, original species of the genus Hosta in China, were studied. N 4 (4 g of CRNF per pot), N 8 (8 g of CRNF per pot), and sometimes N 12 (12 g of CRNF per pot), significantly increased total dry weights, net photosynthetic rate ( P
N), stomatal conductance ( g
s), transpiration rate ( E), the maximum quantum yield of PSII photochemistry ( F
v/ F
m), the maximum ratio of quantum yields of photochemical and concurrent nonphotochemical processes in PSII ( F
v/ F
0), actual efficiency of photochemical energy conversion in PSII under light (Φ PSII), and photochemical quenching coefficient (qP), but significantly decreased internal CO 2 concentration ( C
i) and nonphotochemical Chl fluorescence quenching (NPQ) compared to control plants at different growth stages of the two Hosta species in two levels of light intensities (50% of natural light (L 50) and 70% of natural light (L 70)). Based on the available data, we concluded that the increments in total dry weights of Hosta clausa var. ensata and Hosta ventricosa by appropriate amount of CRNF supply treatments under L 50 and/or L 70 light conditions are directly related to the increments in the P
N, which may be due to both stomatal and nonstomatal improvements for a longer growing time. Furthermore, there was an interaction
between light intensity and CRNF supply treatments on growth and photosynthetic characteristics of the two Hosta species. The adaptability of Hosta plants with obvious stoloniferous rootstock to stronger light was higher than that of Hosta plants without obvious stoloniferous rootstock. 相似文献
2.
In this study, the gas exchange, chlorophyll fluorescence, and antioxidant activity in eight tall fescue cultivars were investigated
under aluminum stress. The results showed that the net photosynthetic rate ( P
N) and stomatal conductance ( g
s) were decreased, while the intercellular CO 2 concentration (C i) was stable or increased under Al stress conditions. The efficiency of excitation capture by open PSII reaction centers ( F′ v/ F′ m), the maximum quantum yield of PSII photochemistry ( F
v/ F
m), the quantum yield of PSII electron transport (Φ PSII), and the photochemical quenching (qP) were also decreased after Al stress, while the non-photochemical quenching (NPQ) was
increased. Moreover, Al stress increased the antioxidant activities and MDA contents in each tall fescue cultivars. However,
there was a lot genotype differences between the Al-tolerant and Al-sensitive cultivars. Cv. Barrington was the most sensitive
cultivar and cv. Crossfire 2 was the most tolerant cultivar. The excessive excitation energy could not be dissipated efficiently
by antenna pigments, and reactive oxygen species could not be scavenged efficiently, thereby resulting in membrane lipid peroxidation
in cv. Barrington under Al stress conditions. 相似文献
3.
Seedling performance may determine plant distribution, especially in water-limited environments. Plants of Caragana korshinskii commonly grow in arid and semiarid areas in northwestern China, and endure water shortage in various ways, but little is
known about their performance when water shortage occurs at early growth stages. The water relations, photosynthetic activity,
chlorophyll (Chl) content and proline accumulation were determined in 1-year-old seedlings growing in a 1:1 mixture of Loess
soil and Perlite and subjected to ( 1) a water deficit for 20 days and ( 2) kept adequately watered throughout. The water deficit induced low (−6.1 MPa) predawn leaf water potentials (LWP), but did
not induce any leaf abscission. Stomatal conductance ( g
s), leaf transpiration rate ( E), and net photosynthetic rate ( P
N) decreased immediately following the imposition of the water deficit, while the maximal photochemical efficiency of photosystem
II (PSII) (F v/F m) and the effective quantum yield of PSII (Φ PSII) decreased 15 days later. An early and rapid decrease in g
s, reduced E, increased Chl ( a+b) loss, increased the apparent rate of photochemical transport of electrons through PSII (ETR)/ P
N, as well as a gradual increase in non-photochemical quenching of fluorescence (NPQ) and proline may have contributed to preventing
Φ PSII from photodamage. C. korshinskii seedlings used a stress-tolerance strategy, with leaf maintenance providing a clear selective advantage, considering the
occasional rainfall events during the growing season. 相似文献
4.
Wheat plants grown in controlled growth chambers were exposed to drought stress (DS) and high temperature (HT) singly and
in combination (DS+HT). The effects of these two stresses on net photosynthetic rate ( P
N), stomatal conductance ( g
s), intercellular CO 2 concentration ( C
i), quantum efficiency of photosystem 2 (Φ PS2), variable to maximum chlorophyll (Chl) fluorescence (F v/F m), photochemical (q p) and non-photochemical (NPQ) Chl fluorescence, and yield were investigated. Grain yield was decreased by 21 % due to DS,
while it was increased by 26 % due to HT. P
N, g
s, C
i, and Chl fluorescence were dramatically reduced to DS, HT, and their interaction, except NPQ which showed an increase due
to HT. 相似文献
5.
The effects of 10 mM putrescine (Put) treated by spraying on leaves on growth, chlorophyll content, photosynthetic gas-exchange
characteristics, and chlorophyll fluorescence were investigated by growing cucumber plants ( Cucumis sativus L. cv. ChangChun mici) using hydroponics with or without 65 mM NaCl as a salt stress. Salt stress caused the reduction of
growth such as leaf area, root volume, plant height, and fresh and dry weights. Furthermore, net photosynthesis rate ( P
n), stomatal conductance ( g
s), intercellular CO 2 concentration ( C
i), and transpiration rate ( T
r) were also reduced by NaCl, but water use efficiency (WUE; P
n/ T
r) showed a tendency to be enhanced rather than reduced by NaCl. However, Put alleviated the reduction of P
n by NaCl, and showed a further reduction of C
i by NaCl. The reduction of g
s and T
r by NaCl was not alleviated at all. The enhancement of WUE by NaCl was shown to have no alleviation at day 1 after starting
the treatment, but after that, the enhancement was gradually reduced till the control level. Maximum quantum efficiency of
PSII ( F
v/ F
m) showed no effects by any conditions based on the combination of NaCl and Put, and in addition, kept constant values in plants
grown in each nutrient solution during this experimental period. The efficiency of excitation energy capture by open photosystem
II (PSII) ( F
v′/ F
m′), actual efficiency of PSII (Φ PSII), and the coefficient on photochemical quenching (qP) of plants with NaCl were reduced with time, and the reduction was alleviated
till the control level by treatment with Put. The F
v′/ F
m′, Φ PSII, and qP of plants without NaCl and/or with Put showed no variation during the experiment. Non-photochemical quenching of
the singlet excited state of chlorophyll a (NPQ) showed quite different manner from the others as mentioned above, namely, continued to enhance during the experiment. 相似文献
6.
Chlorophyll (Chl) fluorescence of warm day/cool night temperature exposed Phalaenopsis plants was measured hourly during 48 h to study the simultaneous temperature and irradiance response of the photosynthetic
physiology. The daily pattern of fluorescence kinetics showed abrupt changes of photochemical quenching (q P), non-photochemical quenching (NPQ) and quantum yield of photosystem II electron transport (Φ PSII) upon transition from day to night and vice versa. During the day, the course of Φ PSII and NPQ was related to the air temperature pattern, while maximum quantum efficiency of PSII photochemistry (F v/F m) revealed a rather light dependent response. Information on these daily dynamics in fluorescence kinetics is important with
respect to meaningful data collection and interpretation. 相似文献
7.
Three prevalent aliphatic polyamines (PAs) include putrescine, spermidine, and spermine; they are low-molecular-mass polycations involved in many physiological processes in plants, especially, under stressful conditions. In this experiment, three bean (Phaseolus vulgaris L.) genotypes were subjected to well-watered conditions and two moderate and severe water-stressed conditions with and without spermidine foliar application. Water stress reduced leaf relative water content (RWC), chlorophyll contents, stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate, maximal quantum yield of PSII (Fv/Fm), net photosynthetic rate (PN), and finally grain yield of bean plants. However, spermidine application elevated RWC, gs, Ci, Fv/Fm, and PN, which caused an increase in the grain yield and harvest index of bean plants under water stress. Overall, exogenous spermidine could be utilized to alleviate water stress through protection of photosynthetic pigments, increase of proline and carotenoid contents, and reduction of malondialdehyde content. 相似文献
8.
Trehalose can reduce stomatal aperture by a hydrogen-peroxide-dependent pathway in Vicia faba L. (cv. Daqingpi) resulting in significantly lower values of net photosynthetic rate (P N), stomatal conductance (g s), and transpiration rate (E). At 8 and 24 h, the lower P N in trehalose-treated plants was accompanied by significant decrease in intercellular CO 2 concentration (c i) suggesting that the reduction of P N was caused by stomatal limitation. At 48 and 72 h, trehalose decreased apparent carboxylation efficiency (P N/c i) and did not decrease c i and g s compared with controls; therefore the reduction in photosynthesis was caused by non-stomatal limitation. Trehalose treatment resulted in significantly higher effective photochemical efficiency of PS II (Φ PSII) and did not affect maximum photochemical efficiency of PS II (F v/F m). At 24, 48, and 72 h, trehalose decreased non-photochemical quenching (NPQ) and increased photochemical quenching (qP). Our results suggest that trehalose did not damage photosynthetic reaction centers. 相似文献
9.
This work aimed to evaluate if gas exchange and PSII photochemical activity in maize are affected by different irradiance
levels during short-term exposure to elevated CO 2. For this purpose gas exchange and chlorophyll a fluorescence were measured on maize plants grown at ambient CO 2 concentration (control CO 2) and exposed for 4 h to short-term treatments at 800 μmol(CO 2) mol −1 (high CO 2) at a photosynthetic photon flux density (PPFD) of either 1,000 μmol m −2 s −1 (control light) or 1,900 μmol m −2 s −1 (high light). At control light, high-CO 2 leaves showed a significant decrease of net photosynthetic rate ( P
N) and a rise in the ratio of intercellular to ambient CO 2 concentration ( C
i/ C
a) and water-use efficiency (WUE) compared to control CO 2 leaves. No difference between CO 2 concentrations for PSII effective photochemistry (Φ PSII), photochemical quenching (q p) and nonphotochemical quenching (NPQ) was detected. Under high light, high-CO 2 leaves did not differ in P
N, C
i/ C
a, Φ PSII and NPQ, but showed an increase of WUE. These results suggest that at control light photosynthetic apparatus is negatively
affected by high CO 2 concentration in terms of carbon gain by limitations in photosynthetic dark reaction rather than in photochemistry. At high
light, the elevated CO 2 concentration did not promote an increase of photosynthesis and photochemistry but only an improvement of water balance due
to increased WUE. 相似文献
10.
研究海岛棉( Gossypium barbadense)和陆地棉( G. hirsutum)两个棉花栽培种的光合作用特性, 探讨两个栽培种光合机构的光抑制以及防御保护机制, 以期为新疆棉花高光效品种选育和高产高效栽培实践提供理论基础。在新疆生态气候条件下, 系统测定了海岛棉和陆地棉的叶片运动、叶片接受光量子通量密度( PFD)、叶片温度、叶绿素荧光参数、气体交换参数和光呼吸速率的日变化。研究结果表明: 陆地棉叶片的“横向日性”较强而海岛棉较弱, 导致海岛棉叶片接受 PFD较低, 但其叶片温度较高。海岛棉叶片的光合速率和气孔导度均显著低于陆地棉。在8:00-10:00 (北京时间, 下同)海岛棉叶片的光呼吸速率略低于陆地棉, 其余时间段海岛棉和陆地棉叶片的光呼吸速率相似。不同栽培种间, 叶片的最大光化学效率和实际光化学效率的日变化均无明显差异。除14:00-16:00以外, 海岛棉叶片的表观电子传递速率和光化学猝灭系数均显著低于陆地棉。8:00以后, 海岛棉叶片的非光化学猝灭显著高于陆地棉。因此, 在新疆生态气候条件下, 海岛棉和陆地棉叶片“横向日性”运动能力和气孔导度的差异导致叶片所处的光温环境不同, 同时造成海岛棉叶片的碳同化能力较低。为阻止光合电子传递链的过度还原, 减轻光合机构的光抑制, 陆地棉叶片主要通过光合机构的电子流途径耗散激发能, 而海岛棉叶片通过热耗散途径和相对较高的光呼吸能力来耗散激发能。 相似文献
11.
To investigate how excess excitation energy is dissipated in a ribulose-1,5-bisphospate carboxylase/oxygenase activase antisense
transgenic rice with net photosynthetic rate ( P
N) half of that of wild type parent, we measured the response curve of P
N to intercellular CO 2 concentration ( C
i), electron transport rate (ETR), quantum yield of open photosystem 2 (PS2) reaction centres under irradiation (F v′/F m′), efficiency of total PS2 centres (Φ PS2), photochemical (q P) and non-photochemical quenching (NPQ), post-irradiation transient increase in chlorophyll (Chl) fluorescence (PITICF), and
P700 + re-reduction. Carboxylation efficiency dependence on C
i, ETR at saturation irradiance, and F v′/F m′, Φ PS2, and q P under the irradiation were significantly lower in the mutant. However, NPQ, energy-dependent quenching (q E), PITICF, and P700 + re-reduction were significantly higher in the mutant. Hence the mutant down-regulates linear ETR and stimulates cyclic electron
flow around PS1, which may generate the ΔpH to support NPQ and q E for dissipation of excess excitation energy. 相似文献
12.
To investigate whether brassinosteroids (BRs) could be used to alleviate chill-induced inhibition of photosynthesis in cucumber
( Cucumis sativus L) during chilling and subsequent recovery, the effects of exogenously applied 24-epibrassinolide (EBR) on gas exchange,
chlorophyll fluorescence parameters, and antioxidant enzyme activity were studied. Cucumber plants were exposed to chilling
under low light (12/8°C and 100 μmol m −2 s −1 PPFD) for 3 days and then recovered under normal temperature and high irradiance (28/18°C and 600 μmol m −2 s −1 PPFD) for 6 days. Chilling significantly decreased the net photosynthetic rate ( P
N) and stomatal conductance ( g
s), and increased rate of O 2
·− formation and H 2O 2 and malondialdehyde (MDA) content in cucumber leaves, but did not influence the optimal quantum yield of PSII (F v/F m). Chilling also decreased the effective quantum yield of PSII photochemistry (Φ PSII) and photochemical quenching (q P), but induced an increase in nonphotochemical quenching (NPQ), and the activities of superoxide dismutase (SOD) and ascorbate
peroxidase (APX). High irradiance (600 μmol m −2 s −1) further aggravated the decrease in P
N, g
s, Φ PSII and q P, and enhanced the increase in reactive oxygen species (ROS) generation and accumulation in the first day of recovery after
chilling. However, high irradiance induced a sharp decrease in F v/F m and NPQ, as well as the activities of SOD and APX on the first day of recovery. EBR pretreatment significantly alleviated
chill-induced inhibition of photosynthesis during chilling stress and subsequent recovery period, which was mainly due to
significant increases in g
s, Φ PSII, q P and NPQ. EBR pretreatment also reduced ROS generation and accumulation, and increased the activities of SOD and APX during
chilling and subsequent recovery. Those results suggest that EBR pretreatment alleviates the chill reduction in photosynthesis
and accelerated the recovery rate mainly by increasing of the stomatal conductance, the efficiency of utilization and dissipation
of leaf absorbed light, and the activity of the ROS scavenging system during chilling and subsequent recovery period. 相似文献
13.
In order to investigate the effect of chromosome doubling on ozone tolerance, we compared the physiological responses of a
diploid honeysuckle ( Lonicera japonica Thunb.) and its autotetraploid cultivar to elevated ozone (O 3) exposure (70 ng g −1, 7 h d −1 for 31 d). Net photosynthetic rate ( P
N) of both cultivars were drastically ( P<0.01) impaired by O 3. Although there were significantly positive correlation between P
N and stomatal conductance ( g
s) in both cultivars under each treatment, the decreased g
s in O 3 might be the result rather than the cause of decreased P
N as indicated by stable or increasing the ratio of intercellular to ambient CO 2 concentration( C
i/ C
a). P
N under saturating CO 2 concentration ( P
Nsat) and carboxylation efficiency (CE) significantly decreased under O 3 fumigation, which indicated the Calvin cycle was impaired. O 3 also inhibited the maximum efficiency of photosystem II (PSII) photochemistry in the dark-adapted state (F v/F m), actual quantum yield of PSII photochemistry (Φ PSII), electron transport rate (ETR), photochemical quenching coefficient (qP), non-photochemical quenching (NPQ), the maximum
in vivo rate of Rubisco carboxylation (V cmax) and the maximal photosynthetic electron transport rate (J max) which demonstrated that the decrease in P
N of the honeysuckle exposed to elevated O 3 was probably not only due to impairment of Calvin cycle but also with respect to the light-harvesting and electron transport
processes. Compared to the diploid, the tetraploid had higher relative loss in transpiration rate ( E), ( g
s), ( P
Nsat), V cmax and J max. This result indicated that the Calvin cycle and electron transport in tetraploid was damaged more seriously than in diploid.
A barely nonsignificant ( P=0.086) interaction between O 3 and cultivar on P
N suggested a higher photosynthetic sensitivity of the tetraploid cultivar. 相似文献
14.
Photosynthesis, chlorophyll (Chl) a fluorescence, and nitrogen metabolism of hawthorn ( Crataegus pinnatifida Bge.), subjected to exogenous L-glutamic acid (GLA) (200 mg l −1, 400 mg l −1, and 800 mg l −1) that possibly affect secondary metabolic regulation, were measured. The results indicated that photosynthetic and fluorescence
characteristics of hawthorn exhibited positive responses to the application of GLA. Different concentrations of GLA caused
an increase in Chl content, net photosynthetic rate ( P
N) and stomatal conductance ( g
s) as well as transpiration rate ( E), and improved the carboxylation efficiency (CE), apparent quantum yield (AQY) and maximum carboxylation velocity of Rubisco
(V cmax). Application of GLA could also enhance the maximum ratio of quantum yields of photochemical and concurrent non-photochemical
processes in PSII (F v/F 0), the maximal quantum yield of PSII (F v/F m), the probability that an absorbed photon will move an electron into the electron transport chain beyond Q A (Φ Eo) as well as the performance index on absorption basis (PI ABS), but decreased the intercellular CO 2 concentration ( C
i) and the minimal fluorescence (F 0). Application of GLA also induced an increase in nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2)
activities, and increased the soluble protein content, leaf nitrogen (N) content and N accumulation in leaves as well as the
plant biomass. However, the effects were different among different concentrations of GLA, and 800 mg l −1 GLA was better. This finding suggested that application of GLA is recommended to improve the photosynthetic capacity by increasing
the light energy conversion and CO 2 transfer as well as the photochemical efficiency of PSII, and enhanced the nitrogen metabolism and growth and development
of plants. 相似文献
15.
Plants of C. canephora grown in pots under low nitrogen (LN) or high nitrogen (HN) applications were submitted to either cyclic water stress or daily irrigation. Water deficit led to marked decreases in net carbon assimilation rate ( A) and, to a lesser extent, in stomatal conductance ( gs), regardless of the N treatments. In well-watered plants, A appreciably increased in HN plants relative to LN plants without significant changes in gs. As a whole, changes in internal CO 2 concentration predominantly reflected changes in A rather than in gs. Under irrigated conditions, A, but not gs, correlated with leaf N concentration in a curvilinear way. Photosynthetic nitrogen-use efficiency was considerably low, and decreased with increasing leaf N concentration. Limited N, but not water, slightly decreased the maximum photochemical efficiency of photosystem II (PSII). Under continuous irrigation, LN plants had a smaller quantum yield of electron transport ( PSII) through slight decreases of photochemical quenching (q p) and capture efficiency of excitation energy by open PSII reaction centres, and increases in Stern-Volmer non-photochemical quenching. Under water-stressed conditions, changes in PSII photochemistry were apparent only in HN plants, with a 25 % decrease in PSII, due mainly to variations in q p. Biochemical constraints, rather than stomatal or photochemical limitations, provoked the decreases in A under limited supply of either N or water. 相似文献
16.
In order to investigate the effect of day/night temperature difference (DIF) on photosynthetic characteristics of tomato plants ( Solanum lycopersicum, cv. Jinguan 5) at fruit stage, an experiment was carried out in climate chambers. Five day/night temperature regimes (16/34, 19/31, 25/25, 31/19, and 34/16°C) with respective DIFs of -18, -12, 0, +12, and +18 were used and measured at mean daily temperature of 25°C. The results showed that chlorophyll (Chl) a, Chl b, net photosynthetic rate ( PN), stomatal conductance (g s), maximum quantum yield of PSII photochemistry (F v/F m), effective quantum yield of PSII photochemistry (? PSII), and photochemical quenching (qp) significantly increased under positive DIF, while they decreased with negative DIF. In contrast, the Chl a/b ratio and nonphotochemical quenching (NPQ) decreased under positive DIF, while increased with negative DIF. Chl a, Chl b, PN, g s, F v/F m, ? PSII, and qp were larger under +12 DIF than those at +18 DIF, while Chl a/b and NPQ showed an opposite trend. 相似文献
17.
The influence of long‐term drought stress on photosynthesis of Japanese mountain birch ( Betula ermanii Cham.) was examined using chlorophyll fluorescence and gas exchange measurements. Drought stress was imposed in potted plants by reducing irrigation frequency from daily (control) to twice‐weekly and once‐weekly. Thirty‐day‐old leaves, which had developed under fully stressed conditions, were used for the measurements. The decline in net CO 2 assimilation rate (A) observed in situ in drought‐stressed plants resulted from a lower intercellular CO 2 concentration (C i) due to stomatal closure but the carboxylation efficiency was not affected as there was no difference in the initial slope of the A/C i response after watering. Although there were no treatment differences in A at C i below 270 μmol mol ?1 (with ambient air at 360 μmol mol ?1 CO 2), higher electron transport rate (ETR), photochemical quenching (q P) and the efficiency of energy conversion of open PSII (F v′/F m′), and similar or even lower non‐photochemical quenching (NPQ) were observed at a given C i in drought‐stressed plants (of both twice‐ and once‐weekly irrigation), suggesting a higher fraction of open PSII resulting from energy dissipation achieved through higher electron flow rather than through thermal dissipation in PSII antennae. The once‐weekly watered plants showed a lower ratio of gross carbon assimilation rate to ETR (A*/ETR), suggesting an enhanced alternative pathway of electron flow probably involving the Mehler‐peroxidase (MP) reaction as indicated by a higher Φ PSII at a given Φ CO2 under non‐photorespiratory conditions. On the other hand, plants of twice‐weekly watering exhibited almost the same A*/ETR and Φ PSII–Φ CO2 relationship as control plants, indicating no enhanced alternative pathways under mild drought stress. 相似文献
18.
Kalanchoë daigremontiana, a CAM plant grown in a greenhouse, was subjected to severe water stress. The changes in photosystem II (PSII) photochemistry were investigated in water‐stressed leaves. To separate water stress effects from photoinhibition, water stress was imposed at low irradiance (daily peak PFD 150 μmol m ?2 s ?1). There were no significant changes in the maximal efficiency of PSII photochemistry ( Fv/ Fm), the traditional fluorescence induction kinetics (OIP) and the polyphasic fluorescence induction kinetics (OJIP), suggesting that water stress had no direct effects on the primary PSII photochemistry in dark‐adapted leaves. However, PSII photochemistry in light‐adapted leaves was modified in water‐stressed plants. This was shown by the decrease in the actual PSII efficiency ( ΦPSII), the efficiency of excitation energy capture by open PSII centres ( Fv′/ Fm′), and photochemical quenching ( qP), as well as a significant increase in non‐photochemical quenching (NPQ) in particular at high PFDs. In addition, photoinhibition and the xanthophyll cycle were investigated in water‐stressed leaves when exposed to 50% full sunlight and full sunlight. At midday, water stress induced a substantial decrease in Fv/ Fm which was reversible. Such a decrease was greater at higher irradiance. Similar results were observed in ΦPSII, qP, and Fv′/ Fm′. On the other hand, water stress induced a significant increase in NPQ and the level of zeaxanthin via the de‐epoxidation of violaxanthin and their increases were greater at higher irradiance. The results suggest that water stress led to increased susceptibility to photoinhibition which was attributed to a photoprotective process but not to a photodamage process. Such a photoprotection was associated with the enhanced formation of zeaxanthin via de‐epoxidation of violaxanthin. The results also suggest that thermal dissipation of excess energy associated with the xanthophyll cycle may be an important adaptive mechanism to help protect the photosynthetic apparatus from photoinhibitory damage for CAM plants normally growing in arid and semi‐arid areas where they are subjected to a combination of water stress and high light. 相似文献
19.
Australian carnivorous pitcher plant Cephalotus follicularis Labill. produces two types of leaves. During the spring time, the plant produces a foliage type of noncarnivorous leaf called
lamina. Later, the second type of leaf is produced — carnivorous pitcher. Using simultaneous measurements of gas exchange
and chlorophyll (Chl) fluorescence photosynthetic efficiency of these two distinct forms of leaves were compared. In addition
stomatal density, an important component of gas exchange, and Chl concentration were also determined. Pitcher trap had lower
net photosynthetic rate ( P
N) in comparison to noncarnivorous lamina, whereas the rate of respiration ( R
D) was not significantly different. This was in accordance with lower stomatal density and Chl concentration in the pitcher
trap. On the other hand maximum quantum yield of PSII (F v/F m) and effective quantum yield of photochemical energy conversion in PSII (Φ PSII) was not significantly different. Nonphotochemical quenching (NPQ) was significantly higher in the lamina at higher irradiance.
These data are in accordance with hypothesis that changing the leaf shape in carnivorous plants to make it a better trap generally
makes it less efficient at photosynthesis. However, the pitcher of Cephalotus had much higher P
N than it was expected from the data set of the genus Nepenthes. Because it is not possible to optimize for contrasting function such as photosynthesis and carnivory, it is hypothesized
that Cephalotus pitchers are less elaborated for carnivorous function than the pitchers of Nepenthes. 相似文献
20.
通过比较棉花( Gossypium hirsutum)幼叶和完全展开叶气体交换参数及叶绿素荧光特性的差异, 探讨高光强下幼叶的光抑制程度及明确光保护机制间的协调机理。在田间自然条件下, 以棉花刚展平的幼嫩叶片(幼叶)和面积已达到最大的完全展开叶片为研究对象, 通过测定不同发育阶段叶片气体交换参数及叶绿素a荧光参数的变化, 并运用Dual-PAM100对不同发育阶段的叶片进行快速光响应曲线的拟合。结果表明: 幼叶和完全展开叶片在光合、荧光特性方面表现出明显的差异。与完全展开叶相比, 较低的叶绿素(Chl)含量和气孔导度( Gs)是幼叶较低净光合速率( Pn)的限制因素, 从而直接导致其光系统II (PSII)实际光化学效率( ΦPSII)和光化学猝灭系数( qP)的降低。在1800 μmol·m -2·s -1光强以下, 完全展开叶具有较强的围绕PSI循环的电子流(CEF), 有利于合成ATP, 是其具有较高光合能力的原因之一。相同光强下, 幼叶较低的光饱和点( LSP)更易受光抑制, 但其PSII原初光化学效率( Fv/ Fm)的日变化幅度显著小于完全展开叶, 说明强光下幼叶通过类胡萝卜素(Car)猝灭单线态氧、光呼吸( Pr)、热耗散( NPQ)以及PSI-CEF等光保护机制能有效地耗散过剩的光能, 从而避免其光合机构发生光抑制。 相似文献
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