New theory predicts a steeper than ‘expected’ response of water use efficiency to CO2 and vapour pressure deficit

2016 ◽  
Author(s):  
Iain Colin Prentice
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Use Efficiency

Partial rootzone drying increases water-use efficiency of lemon Fino 49 trees independently of root-to-shoot ABA signalling

2012 ◽  
Vol 39 (5) ◽  
pp. 366 ◽  
Author(s):  
J. G. Pérez-Pérez ◽  
I. C. Dodd ◽  
P. Botía
Keyword(s):  
Stomatal Conductance ◽  
Water Use Efficiency ◽  
Water Potential ◽  
Water Use ◽  
Leaf Water Potential ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Leaf Water ◽  
Use Efficiency ◽  
Partial Rootzone Drying

To determine whether irrigation strategy altered the sensitivity of Citrus leaf gas exchange to soil, plant and atmospheric variables, mature (16-year-old) Fino 49 lemon trees (Citrus limon (L.) Burm. fil. grafted on Citrus macrophylla Wester) were exposed to three irrigation treatments: control (irrigated with 100% of crop potential evapotranspiration, ETc), deficit irrigation (DI) and partial rootzone drying (PRD) treatments,which received 75% ETc during the period of highest evaporative demand and 50% ETc otherwise. Furthermore, to assess the physiological significance of root-to-shoot ABA signalling, the seasonal dynamics of leaf xylem ABA concentration ([X-ABA]leaf) were evaluated over two soil wetting–drying cycles during a 2-week period in summer. Although stomatal conductance (gs) declined with increased leaf-to-air vapour pressure deficit (LAVPD), lower leaf water potential and soil water availability, [X-ABA]leaf was only related to stomatal closure in well irrigated trees under moderate (<2.5 kPa) atmospheric vapour pressure deficit (VPD). Differences in [X-ABA]leaf were not detected between treatments either before or immediately after (<12 h) rewatering the dry side of PRD trees. Leaf water potential was higher in control trees, but decreased similarly in all irrigation treatments as daily LAVPD increased. In contrast, DI and PRD trees showed lower stomatal sensitivity to LAVPD than control trees. Although DI and PRD decreased stomatal conductance and photosynthesis, these treatments did not significantly decrease yield, but PRD increased crop water use efficiency (WUE) by 83% compared with control trees. Thus PRD-induced enhancement of crop WUE in a semiarid environment seems to involve physiological mechanisms other than increased [X-ABA]leaf.

Effect of Leaf Position, Expansion and Age on Photosynthesis, Transpiration and Water Use Efficiency of Cotton

1980 ◽  
Vol 7 (1) ◽  
pp. 89 ◽  
Author(s):  
GA Constable ◽  
HM Rawson
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Dark Respiration ◽  
Vapour Pressure Deficit ◽  
Initial Slope ◽  
Photon Flux ◽  
Morphological Development ◽  
Leaf Position ◽  
Leaf Unfolding ◽  
Use Efficiency

Net photosynthesis, dark respiration and the response to photon flux density were measured on cotton leaves grown in a glasshouse. Leaves at four positions on the plant were examined from their unfolding until 70 days later. Photosynthesis and transpiration per unit of leaf area were unaffected by leaf position and, in all leaves, peak photosynthesis of about 110 ng CO2 cm-2 s-1 was attained 13-15 days after leaf unfolding, when the leaf was 75-90% of maximum area. Photosynthesis was maintained at this rate for only 12 days before declining linearly to values 20% of the maximum when leaves were 70 days old. Transpiration followed a similar pattern reaching a maximum of about 13 �g H2O cm-2 s-1 at 2 kPa vapour pressure deficit (VPD) at 13 days. Stomatal and internal conductances changed in parallel as leaves aged, with the consequence that internal CO2 concentration and water use efficiency remainedessentially constant at 220�ll-1 and 16.8 ng CO2 (�g H2O kPa VPD-1)-1 respectively. Youngest and oldest leaves saturated at lowest light levels (400-800 pE m-2 s-1) while 16-18- day-old leaves had light saturation at 1100 �E m-2 s-1. The initial slope of the light response curves increased as leaves expanded up to 10 days age then remained constant at 0.25 ng CO2 cm-2 (pE m-2)-1. Dark respiration reached a maximum of 1.5 ng CO2 mg-1 s-1 5 days after leaf unfolding, when leaf dry weight was increasing most rapidly. The relationship between the consistent pattern of gas exchange with age and the pattern of morphological development is discussed, along with internal factors associated with age-dependent photosynthesis.

Growth and yield response of barley and chickpea to water stress under three environments in southeast Queensland. III. Water use efficiency, transpiration efficiency and soil evaporation

1995 ◽  
Vol 46 (1) ◽  
pp. 49 ◽  
Author(s):  
s Thoma ◽  
S Fukai
Keyword(s):  
Water Stress ◽  
Water Use Efficiency ◽  
Water Use ◽  
Vapour Pressure Deficit ◽  
Soil Evaporation ◽  
Growth And Yield ◽  
Yield Response ◽  
Transpiration Efficiency ◽  
Canopy Development ◽  
Use Efficiency

Two cultivars of barley and one cultivar of chickpea were grown in both well-watered and water stress conditions in three experiments. Water use efficiency (biomass produced per unit evapotranspiration) was lower in chickpea than in barley, and between two barley cultivars it was higher in early-maturing Corvette than in late-maturing Triumph. These differences in water use efficiency were mostly related to the differences in transpiration efficiency (biomass produced per unit transpiration). The latter appeared to reflect the differences in biomass production under well-watered conditions, as similar differences were found in light use efficiency (biomass produced per unit of photosynthetically active radiation intercepted) among the three crops. Transpiration efficiency was inversely related to vapour pressure deficit of the air. In three experiments soil evaporation accounted for about 55% and 10-30% of total water use for chickpea and barley respectively during observation periods, when rainfall was excluded from the plots. Slow canopy development of chickpea was a reason for such a high proportion of soil evaporation, and this contributed to its lower water use efficiency compared to barley. The amount of radiation transmitted to the soil surface appeared to be an important factor determining soil evaporation, even when soil water was not fully available and limiting soil evaporation.

Photosynthesis and Transpiration in Dicotyledonous Plants. II. Expanding and Senescing Leaves of Soybean

1976 ◽  
Vol 3 (2) ◽  
pp. 257 ◽  
Author(s):  
RG Woodward ◽  
HM Rawson
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Vapour Pressure Deficit ◽  
Net Photosynthesis ◽  
Unit Leaf ◽  
Efficiency Parameter ◽  
Dicotyledonous Plants ◽  
History Of ◽  
Use Efficiency ◽  
Soybean Leaves

The history of net photosynthesis and transpiration per unit leaf area was determined for intact soybean leaves from their unfolding to senescence during flowering and pod filling on untreated (podded) and partially depodded plants growing in a glasshouse. Leaf diffusive resistances to CO2 were calculated and a water use efficiency parameter was derived (net mass of carbon dioxide fixed per unit mass of water transpired per millibar vapour pressure deficit). Net photosynthesis and transpiration behaved similarly through all stages of leaf development. A number of peaks were evident in these parameters. The first was associated with leaf expansion and occurred when the leaf reached its maximum area. The second peak coincided with flowering of the plant and later peaks occurred during pod filling. Stomatal and mesophyll resistances also exhibited similar behaviour during the life of the leaf; the possible causes of this linkage are discussed. Water use efficiency increased rapidly up to the time of full lamina expansion. Thereafter, it rose slowly or remained stable until leaf senescence approached, when the efficiency declined. Net photosynthesis and transpiration of leaves were very similar in both podded and partially depodded plants. It appears that to prevent a shortage of assimilate during flowering and pod filling, photosynthesis may be maintained or increased in some leaves and the response is not related to the number of pods available for filling. The increases in photosynthesis were correlated with both higher stomatal and mesophyll conductances. Mechanisms by which the plant may control leaf photosynthesis are discussed.

Temperature and water availability effects on radiation and water use efficiencies in alfalfa (Medicago sativa L.)

2005 ◽  
Vol 45 (4) ◽  
pp. 383 ◽  
Author(s):  
D. J. Collino ◽  
J. L. Dardanelli ◽  
M. J. De Luca ◽  
R. W. Racca
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Water Availability ◽  
Vapour Pressure Deficit ◽  
Radiation Use Efficiency ◽  
Annual Rainfall ◽  
Forage Production ◽  
Temperature Regimes ◽  
Use Efficiency ◽  
Radiation Use

Alfalfa, the most important forage crop in Argentina, shows considerable variability in forage production caused by variations in inter-annual rainfall and intra-annual radiation and temperature regimes. Such variation may affect radiation use efficiency and water use efficiency. This paper seeks to study the effects of temperature and water availability on radiation use efficiency and water use efficiency. We conducted the experiment in Córdoba, Argentina, under irrigated and droughted conditions. Drought was imposed by mobile rainout shelters during 3 consecutive periods. We measured forage, intercepted photosynthetically active radiation and water use to calculate radiation use efficiency and water use efficiency between cuttings. Under irrigation, radiation use efficiency and water use efficiency normalised by daytime vapour pressure deficit, were not limited by mean temperature above 21.3 and 21.9°C, respectively. Below those critical values, both variables decreased consistently with temperature decrements. Under drought, radiation use efficiency tended to decrease and water use efficiency tended to increase. In addition, the relationship between relative dry matter and relative water use was not linear, as reported in previous studies for annual crops.

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