Intracellular CO2 Research Articles

Effects of Short-term Hypergravity Exposure on Germination, Growth and Photosynthesis of Triticum aestivum L.

Numerous studies have been carried out to investigate the hypergravity effect on plants, where seedlings (4–5 days old) were continuously exposed and grown under hypergravity condition. Here, we have used a novel ‘shortterm hypergravity exposure experimental method’ where imbibed caryopses (instead of seedlings) were exposed to higher hypergravity values ranging from 500 g to 2500 g for a short interval time of 10 minutes and post short-term hypergravity treated caryopses were grown under 1 g conditions for five days. Changing patterns in caryopsis germination and growth, along with various photosynthetic and biochemical parameters were studied. Results revealed the significant inhibition of caryopsis germination and growth in short-term hypergravity treated seeds over control. Photosynthesis parameters such as chlorophyll content, rate of photosynthesis (PN), transpiration rate (Evap) and stomatal conductance (Gs), along with intracellular CO2 concentration (Cint) were found to be affected significantly in 5 days old seedlings exposed to short-term hypergravity treatment. In order to investigate the cause of observed inhibition, we examined the α-amylase activity and antioxidative enzyme activities. α-amylase activity was found to be inhibited, along with the reduction of sugars necessary for germination and earlier growth in short-term hypergravity treated caryopses. The activities of antioxidant enzymes such as catalase and guaiacol peroxidase were increased in short-term hypergravity treated caryopses, suggesting that caryopses might have experienced oxidative stress upon short-term hypergravity exposure.

Carbon monoxide down-regulates α4β1 integrin-specific ligand binding and cell adhesion: a possible mechanism for cell mobilization.

BackgroundCarbon monoxide (CO), a byproduct of heme degradation, is attracting growing attention from the scientific community. At physiological concentrations, CO plays a role as a signal messenger that regulates a number of physiological processes. CO releasing molecules are under evaluation in preclinical models for the management of inflammation, sepsis, ischemia/reperfusion injury, and organ transplantation. Because of our discovery that nitric oxide signaling actively down-regulates integrin affinity and cell adhesion, and the similarity between nitric oxide and CO-dependent signaling, we studied the effects of CO on integrin signaling and cell adhesion.ResultsWe used a cell permeable CO releasing molecule (CORM-2) to elevate intracellular CO, and a fluorescent Very Late Antigen-4 (VLA-4, α4β1-integrin)-specific ligand to evaluate the integrin state in real-time on live cells. We show that the binding of the ligand can be rapidly down-modulated in resting cells and after inside-out activation through several Gαi-coupled receptors. Moreover, cell treatment with hemin, a natural source of CO, resulted in comparable VLA-4 ligand dissociation. Inhibition of VLA-4 ligand binding by CO had a dramatic effect on cell-cell interaction in a VLA-4/VCAM-1-dependent cell adhesion system.ConclusionsWe conclude that the CO signaling pathway can rapidly down-modulate binding of the VLA-4 -specific ligand. We propose that CO-regulated integrin deactivation provides a basis for modulation of immune cell adhesion as well as rapid cell mobilization, for example as shown for splenic monocytes in response to surgically induced ischemia of the myocardium.

Silicon supplementation improves drought tolerance in canola plants

This paper reports the effects of silicon (Si) supplementation (0.35 g Na2SiO3/kg soil, 2.73 mmol Si/kg soil) on some physiological characteristics of canola (Brassica napus L. cv. Okapi) plants grown in pots and treated with or without Si under water stress for 25 days. In this study, Si-supplied plants showed the higher shoot dry weight (SDW), root dry weight (RDW), relative growth rate (RGR), net assimilation rate (NAR), and relative water content (RWC) as compared to those without application of Si under drought conditions. However, Si did not significantly affect dry weight accumulation under well-watered conditions. CO2 absorbance (A) was increased by silicon under water stress conditions. The intracellular CO2 concentration (Ci), which was significantly elevated under water stress, was decreased by Si. Silicon application significantly increased the root amino acid content after 20 and 25 days of water stress. In Si-supplemented water-deficit plants, the amount of MDA remained unchanged after 25 days of water stress, obviously because of an efficient scavenging following significant enhancement of superoxide dismutase (SOD) and peroxidase (POD) activities. These results indicated that Si ameliorated growth reduction of drought-stressed canola plants, accompanied by an increase in the root water uptake through the formation of more fine roots and more amino acids as osmotica for supporting water uptake. The results of this study revealed that Si application alleviated water stress damages because of the higher water uptake, better photosynthetic rate, and the lowered lipid peroxidation in canola plants.

Carbon Monoxide-releasing Molecule-3 (CORM-3; Ru(CO)3Cl(Glycinate)) as a Tool to Study the Concerted Effects of Carbon Monoxide and Nitric Oxide on Bacterial Flavohemoglobin Hmp

CO and NO are small toxic gaseous molecules that play pivotal roles in biology as gasotransmitters. During bacterial infection, NO, produced by the host via the inducible NO synthase, exerts critical antibacterial effects while CO, generated by heme oxygenases, enhances phagocytosis of macrophages. In Escherichia coli, other bacteria and fungi, the flavohemoglobin Hmp is the most important detoxification mechanism converting NO and O2 to the ion nitrate (NO3(-)). The protoheme of Hmp binds not only O2 and NO, but also CO so that this ligand is expected to be an inhibitor of NO detoxification in vivo and in vitro. CORM-3 (Ru(CO)(3)Cl(glycinate)) is a metal carbonyl compound extensively used and recently shown to have potent antibacterial properties. In this study, attenuation of the NO resistance of E. coli by CORM-3 is demonstrated in vivo. However, polarographic measurements showed that CO gas, but not CORM-3, produced inhibition of the NO detoxification activity of Hmp in vitro. Nevertheless, CO release from CORM-3 in the presence of soluble cellular compounds is demonstrated by formation of carboxy-Hmp. We show that the inability of CORM-3 to inhibit the activity of purified Hmp is due to slow release of CO in protein solutions alone i.e. when sodium dithionite, widely used in previous studies of CO release from CORM-3, is excluded. Finally, we measure intracellular CO released from CORM-3 by following the formation of carboxy-Hmp in respiring cells. CORM-3 is a tool to explore the concerted effects of CO and NO in vivo.

Wheat cultivars selected for high Fv /Fm under heat stress maintain high photosynthesis, total chlorophyll, stomatal conductance, transpiration and dry matter.

The chlorophyll fluorescence parameter Fv /Fm reflects the maximum quantum efficiency of photosystem II (PSII) photochemistry and has been widely used for early stress detection in plants. Previously, we have used a three-tiered approach of phenotyping by Fv /Fm to identify naturally existing genetic variation for tolerance to severe heat stress (3 days at 40°C in controlled conditions) in wheat (Triticum aestivum L.). Here we investigated the performance of the previously selected cultivars (high and low group based on Fv /Fm value) in terms of growth and photosynthetic traits under moderate heat stress (1 week at 36/30°C day/night temperature in greenhouse) closer to natural heat waves in North-Western Europe. Dry matter accumulation after 7 days of heat stress was positively correlated to Fv /Fm . The high Fv /Fm group maintained significantly higher total chlorophyll and net photosynthetic rate (PN ) than the low group, accompanied by higher stomatal conductance (gs ), transpiration rate (E) and evaporative cooling of the leaf (ΔT). The difference in PN between the groups was not caused by differences in PSII capacity or gs as the variation in Fv /Fm and intracellular CO2 (Ci ) was non-significant under the given heat stress. This study validated that our three-tiered approach of phenotyping by Fv /Fm performed under increasing severity of heat was successful in identifying wheat cultivars differing in photosynthesis under moderate and agronomically more relevant heat stress. The identified cultivars may serve as a valuable resource for further studies to understand the physiological mechanisms underlying the genetic variability in heat sensitivity of photosynthesis.

Environmentally driven evolution of Rubisco and improved photosynthesis and growth within the C3 genus Limonium (Plumbaginaceae).

Carbon assimilation by most ecosystems requires ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Its kinetic parameters are likely to have evolved in parallel with intracellular CO2 availability, with the result that faster forms of Rubisco occur in species with CO2 -concentrating mechanisms. The Rubisco catalytic properties were determined and evaluated in relation to growth and carbon assimilation capacity in Mediterranean Limonium species, inhabiting severe stress environments. Significant kinetic differences between closely related species depended on two amino acid substitutions at functionally important residues 309 and 328 within the Rubisco large subunit. The Rubisco of species facing the largest CO2 restrictions during drought had relatively high affinity for CO2 (low Michaelis-Menten constant for CO2 Kc) but low maximum rates of carboxylation (kcatc), while the opposite was found for species that maintained higher CO2 concentrations under similar conditions. Rubisco kinetic characteristics were correlated with photosynthetic rate in both well-watered and drought-stressed plants. Moreover, the drought-mediated decrease in plant biomass accumulation was consistently lower in species with higher Rubisco carboxylase catalytic efficiency (kcatc/Kc). The present study is the first demonstration of Rubisco adaptation during species diversification within closely related C3 plants, revealing a direct relationship between Rubisco molecular evolution and the biomass accumulation of closely related species subjected to unfavourable conditions.

Spike frequency adaptation in avian intrapulmonary chemoreceptors does not rely on Na+/H+ exchange (1092.9)

IPC are essential for avian breath‐by‐breath respiratory control and are inversely sensitive to lung PCO2. Evidence suggests IPC detect intracellular pH rather than molecular CO2, and that pHi reflects a dynamic interaction of intracellular CO2 hydration/dehydration, buffering, and transmembrane acid/base exchange. We used the Na+/H+ exchange (NHE) blocker dimethyl amiloride (DMA) to test NHE’s role in single‐unit IPC response to combined phasic and tonic CO2 step stimuli in anesthetized mallards (n=9). DMA depressed mean (tonic) IPC discharge response to CO2 step stimuli by 15%, 31%, 51%, and 58% at 1,3,8, and 13 µmol/kg, (p<0.05), but did not affect phasic discharge (spike frequency adaptation index, SFA). Depression of tonic CO2 response confirms earlier reports, and the new result that NHE has no effect on the phasic part of IPC step response demonstrates that other mechanisms must underlie SFA.Grant Funding Source: Supported by: NIH R15 HL087269‐02 and R25 GM056931‐15.

The influence of salinity on cell ultrastructures and photosynthetic apparatus of barley genotypes differing in salt stress tolerance

A hydroponic experiment was conducted to elucidate the difference in growth and cell ultrastructure between Tibetan wild and cultivated barley genotypes under moderate (150 mM NaCl) and high (300 mM NaCl) salt stress. The growth of three barley genotypes was reduced significantly under salt stress, but the wild barley XZ16 (tolerant) was less affected relative to cultivated barley Yerong (moderate tolerant) and Gairdner (sensitive). Meanwhile, XZ16 had lower Na+ and higher K+ concentrations in leaves than other two genotypes. In terms of photosynthetic and chlorophyll fluorescence parameters, salt stress reduced maximal photochemical efficiency (F v/F m), net photosynthetic rate (Pn), stomatal conductance (Gs), and intracellular CO2 concentration (Ci). XZ16 showed relatively smaller reduction in comparison with the two cultivated barley genotypes. The observation of transmission electron microscopy found that fundamental cell ultrastructure changes happened in both leaves and roots of all barley genotypes under salt NaCl stress, with chloroplasts being most changed. Moreover, obvious difference could be detected among the three genotypes in the damage of cell ultrastructure under salt stress, with XZ16 and Gairdner being least and most affected, respectively. It may be concluded that high salt tolerance in XZ16 is attributed to less Na+ accumulation and K+ reduction in leaves, more slight damage in cell ultrastructure, which in turn caused less influence on chloroplast function and photosynthesis.

The cry-DASH cryptochrome encoded by the sll1629 gene in the cyanobacterium Synechocystis PCC 6803 is required for Photosystem II repair

The role of the Syn-CRY cryptochrome from the cyanobacterium Synechocystis sp. PCC 6803 has been a subject of research for more than a decade. Recently we have shown that photolyase, showing strong homology with Syn-CRY is required for Photosystem II repair by preventing accumulation of DNA lesions under UV-B (Vass et al. 2013). Here we investigated if Syn-CRY is also involved in PSII repair, either via removal of DNA lesions or other mechanism? The Δsll1629 mutant lacking Syn-CRY lost faster the PSII activity and D1 protein during UV-B or PAR than the WT. However, no detectable damages in the genomic DNA were observed. The transcript levels of the UV-B and light stress indicator gene psbA3, encoding D1, are comparable in the two strains showing that Δsll1629 cells are not defective at the transcriptional level. Nevertheless 2D protein analysis in combination with mass spectrometry showed a decreased accumulation of several, mostly cytoplasmic, proteins including PilA1 and bicarbonate transporter SbtA. Δsll1629 cells exposed to high light also showed a limitation in de novo assembly of PSII. It is concluded that Syn-CRY is required for efficient restoration of Photosystem II activity following UV-B and PAR induced photodamage. This effect is not caused by retardation of DNA repair, instead the synthesis of new D1 (and D2) subunit(s) and/or the assembly of the Photosystem II reaction center complex is likely affected due to the lack of intracellular CO2, or via a so far unidentified pathway that possibly includes the PilA1 protein.

Live-Fibroblast IR Imaging of a Cytoprotective PhotoCORM Activated with Visible Light

Carbon monoxide releasing molecules (CORMs) are an emerging class of pharmaceutical compounds currently evaluated in several preclinical disease models. There is general consensus that the therapeutic effects elicited by the molecules may be directly ascribed to the biological function of the released CO. It remains unclear, however, if cellular internalization of CORMs is a critical event in their therapeutic action. To address the problem of cellular delivery, we have devised a general strategy which entails conjugation of a CO-releasing molecule (here a photoactivated CORM) to the 5'-OH ribose group of vitamin B12. Cyanocobalamin (B12) functions as the biocompatible water-soluble scaffold which actively transports the CORM against a concentration gradient into the cells. The uptake and cellular distribution of this B12-photoCORM conjugate is demonstrated via synchrotron FTIR spectromicroscopy measurements on living cells. Intracellular photoinduced CO release prevents fibroblasts from dying under conditions of hypoxia and metabolic depletion, conditions that may occur in vivo during insufficient blood supply to oxygen-sensitive tissues such as the heart or brain.

Physiological basis of yield variability in wheat (Triticum aestivum L.) under varying degree of shades

Light is the main environmental factor which regulates growth and development of crop plants. Decrease in light intensity due to shading adversely affects plant growth and development. The present study was conducted to analyze the effect of varying degree of shades on physiological characteristics and yield of wheat crop. Two shading treatments were applied i.e. 33 % shading (L1) and 66 % shading (L2) with full sunlight as control (L0). The experiment was conducted for 2 years during the winter seasons of 2010–2011 and 2011–2012 in a split-plot design with three replications with shading treatments in the main plot and five varieties of wheat in the sub plots. The findings of the study showed that photosynthetic rate, stomatal conductance and transpiration rate at 10 days after anthesis (DAA) were significantly reduced while the intracellular CO2 concentration (Ci) increased with increase in shading during both the years. The total chlorophyll content increased whereas, chlorophyll a/b ratio decreased under shading. Grain yield of all the wheat varieties decreased with increase in shading during both the years. Varietal differences in grain yield under shading are discussed in relation to Pn rates and stomatal conductance.

Foliar application of 24-epibrassinolide alleviates high-temperature-induced inhibition of photosynthesis in seedlings of two melon cultivars

Brassinosteroids (BRs), an important class of plant steroidal hormones, play a significant role in the amelioration of various biotic and abiotic stresses. 24-epibrassinolide (EBR), an active brassinosteroid, was applied exogenously in different concentrations to characterize a role of BRs in tolerance of melon (Cucumis melo L.) to high temperature (HT) stress and to investigate photosynthetic performance of HT-stressed, Honglvzaocui (HT-tolerant) and Baiyuxiang (HTsensitive), melon variety. Under HT, Honglvzaocui showed higher biomass accumulation and a lower index of heat injury compared with the Baiyuxiang. The exogenous application of 1.0 mg L−1 EBR, the most effective concentration, alleviated dramatically the growth suppression caused by HT in both ecotypes. Similarly, EBR pretreatment of HTstressed plants attenuated the decrease in relative chlorophyll content, net photosynthetic rate, stomatal conductance, stomatal limitation, and water-use efficiency (WUE), as well as the maximal quantum yield of PSII photochemistry (Fv/Fm), the efficiency of excitation capture of open PSII center, the effective quantum yield of PSII photochemistry (ΦPSII), photochemical quenching coefficient, and the photon activity distribution coefficients of PSI (α). EBR pretreatment further inhibited the increase in intracellular CO2 concentration, leaf transpiration rate, minimal fluorescence of dark-adapted state, nonphotochemical quenching, thermal dissipation, and photon activity distribution coefficients of PSII. Results obtained here demonstrated that EBR could alleviate the detrimental effects of HT on the plant growth by improving photosynthesis in leaves, mainly reflected as up-regulation of photosynthetic pigment contents and photochemical activity associated with PSI.

Is the recovery of (photo) respiratory CO2 and intermediates minimal?

Is the recovery of (photo) respiratory <scp>CO</scp>₂ and intermediates minimal?

BiotecVisions 2012, November

BiotecVisions 2012, November

Gas bubble formation in the cytoplasm of a fermenting yeast

Current paradigms assume that gas bubbles cannot be formed within yeasts although these workhorses of the baking and brewing industries vigorously produce and release CO2 gas. We show that yeasts produce gas bubbles that fill a significant part of the cell. The missing link between intracellular CO2 production by glycolysis and eventual CO2 release from cells has therefore been resolved. Yeasts may serve as model to study CO2 behavior under pressurized conditions that may impact on fermentation biotechnology.

EFFECT OF DEFOLIATION ON LEAF PHYSIOLOGY OF SUGAR BEET CULTIVARS SUBJECTED TO WATER STRESS AND RE-WATERING

Water stress causes defoliation, which can reduce yield and root quality of sugar beets (Beta vulgaris L.) through altered gas exchange characteristics of the leaves. In a two-year experiment, three sugar beet cultivars (Europa, Rival and Corsica) were subjected to three defoliation levels (control-C, moderate-MD, severe-SD) and re-watering after their exposition to drought for a month. Leaf physiological traits including net photosynthesis (A), transpiration rate (E), stomatal conductance (gs), intracellular CO2 (Ci), water use efficiency (WUEL-A/E and WUEi-A/gs), leaf N concentration, petiole NO3-N concentration, specific leaf area (SLA), leaf water potential (WP) and leaf water content (LWC), were determined before defoliation and 15, 30 and 40 days after defoliation (DAD). On contrary to previous reports, water-stressed cultivars differed significantly in their leaf physiology; the late-season cultivar Corsica had the lowest E and gs values without any significant reduction in A. Thus, Corsica was the most water-conservative cultivar. Re-watering rapidly restored leaf physiology but a gradual decline, with the progress of DAD, was evident for A, E, gs and Ci. After re-growth, cultivars differed only in WP and LWC with Europa, the early-harvested cultivar, to have the highest values. Thus, the better response (higher yield increase and lower root quality degradation) of Corsica to re-watering and the subsequent re-growth, as reported by Tsialtas et al. (2009), could be ascribed to its better LAI maintenance compared to Europa and Rival rather than to a better leaf physiological response. The SD plants showed the highest leaf physiological activity since they had the highest A, E, gs and leaf N concentration. The high leaf activity and the low respiration rate are the means by which sugar beets tolerate foliage losses up to 75% and compensate yield losses after defoliation.

Parallel labeling experiments with [U-13C]glucose validate E. coli metabolic network model for 13C metabolic flux analysis

13C-metabolic flux analysis (MFA) is a widely used method for measuring intracellular metabolic fluxes in living cells. 13C MFA relies on several key assumptions: (1) the assumed metabolic network model is complete, in that it accounts for all significant enzymatic and transport reactions; (2) 13C-labeling measurements are accurate and precise; and (3) enzymes and transporters do not discriminate between 12C- and 13C-labeled metabolites. In this study, we tested these inherent assumptions of 13C MFA for wild-type E. coli by parallel labeling experiments with [U-13C]glucose as tracer. Cells were grown in six parallel cultures in custom-constructed mini-bioreactors, starting from the same inoculum, on medium containing different mixtures of natural glucose and fully labeled [U-13C]glucose, ranging from 0% to 100% [U-13C]glucose. Macroscopic growth characteristics of E. coli showed no observable kinetic isotope effect. The cells grew equally well on natural glucose, 100% [U-13C]glucose, and mixtures thereof. 13C MFA was then used to determine intracellular metabolic fluxes for several metabolic network models: an initial network model from literature; and extended network models that accounted for potential dilution effects of isotopic labeling. The initial network model did not give statistically acceptable fits and produced inconsistent flux results for the parallel labeling experiments. In contrast, an extended network model that accounted for dilution of intracellular CO2 by exchange with extracellular CO2 produced statistically acceptable fits, and the estimated metabolic fluxes were consistent for the parallel cultures. This study illustrates the importance of model validation for 13C MFA. We show that an incomplete network model can produce statistically unacceptable fits, as determined by a chi-square test for goodness-of-fit, and return biased metabolic fluxes. The validated metabolic network model for E. coli from this study can be used in future investigations for unbiased metabolic flux measurements.

Effect of Flavone from Forestry Waste &lt;i&gt;C.Cathayensis&lt;/i&gt; Exocarp on Photosynthetic Characteristics of Crops

Using six kinds of concentration (ranged from 0.0 to 2.0mg.L-1) of flavone extract from C.cathayensis exocarp treats corn, soybean, wheat and mung bean seedlings, in order to study the photosynthetic rate, stomatal conductance, transpiration rate, intercellular CO2 on the seedling leaf. Results show that effects of flavone extract (0.1-0.5mg.L-1) increase content of the chlorophyll a, b and total chlorophyll, promote photosynthetic rate, stomatal conductance, transpiration rate, proper increase cell gap inside the CO2 concentration.0.1mg.L-1 treatment effect is the most obvious compare with the control, the total chlorophyll and photosynthetic rate increase by 20.9 % and 21% respectively; More than 0.5mg.L-1, the chlorophyll content, photosynthetic rate, stomatal conductance, transpiration rate decrease, the intercellular CO2 rapid increase. Research shows that, the appropriate concentration of flavone can increase the chlorophyll content in the leaf, promote stomatal opening, increase of intracellular CO2 supply, improve leaf photosynthesis efficiency.

Response of tomato (Solanum lycopersicon) to cadmium toxicity: Growth, element uptake, chlorophyll content and photosynthesis rate

The effect of cadmium (Cd) accumulation on mineral composition in roots and shoots, growth development, chlorophyll and water content of tomato (Solanum lycopersiconMill 63/5F1) seedlings was tested under doses of 0 (control), 10, 50 and 100 µM. Cadmium accumulation was defined by elevated concentrations as 50 to 100 µM in root and shoot tissues. Element uptake by roots and shoot was negatively affected by raise in cadmium concentrations, especially in 100 µM Cd. Root and shoot elongation, root and shoot fresh and dry biomass, leaf area were negatively affected by increasing Cd concentrations. Tissue water content, growth tolerance index, chlorophyll a, chlorophyll b and total chlorophyll content were limited by cadmium toxicity. The addition of Cd in the growth medium also had significant deleterious effect on net photosynthetic rate (Pn) and intracellular CO2 concentration (Ci), with Pn being reduced by 27.2 and 62.1% at 5 μmol/L and 100 µM Cd treatments compared to the control, respectively, while Ciincreased correspondingly by 28.4 and 39.3%. Key words: Cadmium (Cd), toxicity, growth, nutrient, chlorophyll, photosynthesis.

Effect of limited irrigation on diurnal variation in flag-leaf photosynthesis and yield of dryland wheat

在大田条件下, 以“青麦6 号”小麦为试验材料, 研究了5 个灌水处理下旱地冬小麦灌浆期旗叶光合特性日变化和产量的变化。结果表明, 5 个灌水处理净光合速率日变化曲线均为双峰曲线, 但随着灌水次数的增加, “午休”明显减弱。在灌溉低于3 水的情况下, 旗叶的净光合速率、气孔导度都随灌溉量的增加呈上升趋势,均以灌3 水(W3, 拔节水60 mm+孕穗水60 mm+灌浆水60 mm)处理最高, 而胞间CO₂ 浓度和气孔限制值随着灌溉量的增加呈下降趋势; 而灌溉4 水(W4, 起身水60 mm+拔节水60 mm+孕穗水60 mm+灌浆水60 mm)处理的净光合速率明显小于W3 处理, 表明过量灌溉对旱地小麦灌浆期旗叶的光合作用有消极作用。小麦产量以灌2 水(W2, 拔节水60 mm+孕穗水60 mm)处理为最高, 且在灌溉2 水以下随着灌溉次数增加而增加, 但灌1 水(W1, 拔节水60 mm)和W2 处理间产量差异不显著, 同时灌溉3 水(W3)和4 水(W4)会使产量下降, 反而低于旱地处理, 因此过多灌水不利于旱地小麦的高产。试验结果还表明, 拔节期、孕穗期和灌浆期灌溉对旱地小麦旗叶灌浆中期达到较高光合作用至关重要, 而起身水对旱地小麦光合作用无显著影响。拔节期是旱地小麦达到高产最重要的灌溉时期, 拔节~孕穗期为冬小麦需水关键期, 拔节~孕穗水对冬小麦产量和水分利用效率有重要影响。水分生产效率也随着灌水量的增加呈下降趋势。综合产量和水分利用效率因素, 以灌溉拔节水60 mm(W1)处理为达到旱地冬小麦高产的最佳灌溉模式。