Reducing the Evaporative Demand Improves Photosynthesis and Water Use Efficiency of Indoor Cultivated Lettuce

Currently, climate change is affecting considerably the availability of freshwater for agriculture, increasing the need for the optimization of crop water use efficiency. Attempts to use VPD (vapor pressure deficit) modulation to reduce water consumption have been made. However, the effects of VPD on leaf stomatal and hydraulic traits, and on possible tradeoffs between photosynthetic carbon gain and transpiration, are rarely reported. We analyzed photosynthesis (gas-exchange, photochemistry) stomatal and hydraulic-related traits of green (G) and red (R) butterhead lettuce (Lactuca sativa L.) grown under low and high VPD (LV, HV) in a controlled environment. Our results showed that plants developed a higher number of small stomata under LV, allowing better regulation over opening/closing mechanisms and thus increasing net photosynthesis by 18%. LV plants also achieved better performance of the photosystem II and a more efficient water use (increments in ΦPSII and iWUE by 3% and 49%), resulting in enhanced plant growth and reduced need for irrigation. Significant differences between G and R plants were limited to a few traits, and the physiological response under the two VPDs did not show cultivar-specific response. We discuss the role of VPD management as necessary to maximize crop water use by harmonizing photosynthesis and transpiration.

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Drying times: plant traits to improve crop water use efficiency and yield

Journal of Experimental Botany ◽

10.1093/jxb/eraa002 ◽

2020 ◽

Vol 71 (7) ◽

pp. 2239-2252 ◽

Cited By ~ 5

Author(s):

Anthony G Condon

Keyword(s):

Water Use Efficiency ◽

Water Use ◽

Plant Traits ◽

Simulation Modelling ◽

Carbon Gain ◽

Crop Water ◽

Evaporative Demand ◽

Crop Water Use ◽

Crop Simulation ◽

Use Efficiency

Abstract Crop water use efficiency (WUE) has come into sharp focus as population growth and climate change place increasing strain on the water used in cropping. Rainfed crops are being challenged by an upward trend in evaporative demand as average temperatures rise and, in many regions, there is an increased irregularity and a downward trend in rainfall. In addition, irrigated cropping faces declining water availability and increased competition from other users. Crop WUE would be improved by, first, ensuring that as much water as possible is actually transpired by the crop rather than being wasted. Deeper roots and greater early crop vigour are two traits that should help achieve this. Crop WUE would also be improved by achieving greater biomass per unit water transpired. A host of traits has been proposed to address this outcome. Restricting crop transpiration through lower stomatal conductance is assessed as having limited utility compared with traits that improve carbon gain, such as enhancements to photosynthetic biochemistry and responsiveness, or greater mesophyll conductance. Ultimately, the most useful outcomes for improved crop WUE will probably be achieved by combining traits to achieve synergistic benefit. The potential utility of trait combinations is supported by the results of crop simulation modelling.

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High-Throughput Phenotyping of Crop Water Use Efficiency via Multispectral Drone Imagery and a Daily Soil Water Balance Model

Remote Sensing ◽

10.3390/rs10111682 ◽

2018 ◽

Vol 10 (11) ◽

pp. 1682 ◽

Cited By ~ 13

Author(s):

Kelly Thorp ◽

Alison Thompson ◽

Sara Harders ◽

Andrew French ◽

Richard Ward

Keyword(s):

Water Balance ◽

Water Use Efficiency ◽

Soil Water ◽

Water Use ◽

High Throughput ◽

Soil Water Balance ◽

Balance Model ◽

Crop Water ◽

Crop Water Use ◽

Use Efficiency

Improvement of crop water use efficiency (CWUE), defined as crop yield per volume of water used, is an important goal for both crop management and breeding. While many technologies have been developed for measuring crop water use in crop management studies, rarely have these techniques been applied at the scale of breeding plots. The objective was to develop a high-throughput methodology for quantifying water use in a cotton breeding trial at Maricopa, AZ, USA in 2016 and 2017, using evapotranspiration (ET) measurements from a co-located irrigation management trial to evaluate the approach. Approximately weekly overflights with an unmanned aerial system provided multispectral imagery from which plot-level fractional vegetation cover ( f c ) was computed. The f c data were used to drive a daily ET-based soil water balance model for seasonal crop water use quantification. A mixed model statistical analysis demonstrated that differences in ET and CWUE could be discriminated among eight cotton varieties ( p < 0 . 05 ), which were sown at two planting dates and managed with four irrigation levels. The results permitted breeders to identify cotton varieties with more favorable water use characteristics and higher CWUE, indicating that the methodology could become a useful tool for breeding selection.

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