In-field film antitranspirants application shows potential yield protection from flowering 1 stage drought periods in winter canola (Brassica napus L.)

Crop-management solutions that simulate plant water-saving strategies might help to mitigate drought damage in crops. Winter canola (Brassica napus L.) is significantly drought-sensitive from flowering to mid-pod development, and drought periods lead to significant yield losses. In this study, the drought-protection efficacy of different chemicals with antitranspirant activity applied just before key drought-sensitive phenological stages was tested on field-grown canola in two years. Drought was artificially imposed with rain shelters. The results suggest that in-field application of 1 L ha–1 of antitranspirant (Vapor Gard (VG), a.i. di-1-p-menthene) at GS6.0 (BBCH growth scale, initiation of flowering) mitigated drought-induced yield loss leading to a 22% seed-yield benefit on average over 2 years of experiments compared with the unsprayed unirrigated plots. No significant yield responses were found from application at GS7.0, with increasing VG concentrations (i.e. 2 and 4 L ha–1), or with an antitranspirant with short-lasting effectiveness. The data suggest that in field conditions where drought occurs during the flowering stage, application of 1 L ha–1 of VG just before the drought event can reduce yield loss. This result should encourage further work on water-saving management strategies during key drought-sensitive phenological stages as drought mitigation tools in canola and under different environments

Evidence for improved pollen viability as the mechanism for film antitranspirant mitigation of drought damage to wheat yield

Application of film antitranspirant to wheat during late stem extension reduces drought damage to yield, but the mechanism is unknown. Field experiments under rain shelters were conducted over 3 years to test the hypothesis that film antitranspirant applied before meiosis alleviates drought-induced losses of pollen viability, grain number and yield. The film antitranspirant di-1-p-menthene was applied at third-node stage, and meiosis occurred at the early boot stage, with a range of 11–16 days after spray application in different years. Irrigated, unsprayed plots were included under the rain-shelters, and pollen viability, measured in 2 years in these plots, averaged 95.3%. Drought reduced pollen viability to 80.1% in unirrigated, unsprayed plots, but only to 88.6% in unirrigated plots treated with film antitranspirant. Grain number and yield of irrigated plots, measured in all years, were 16 529 m–2 and 9.55 t ha–1, respectively, on average. These were reduced by drought to 11 410 m–2 and 6.31 t ha–1 in unirrigated, unsprayed plots, but only to 12 878 m–2 and 6.97 t ha–1 in unirrigated plots treated with film antitranspirant. Thus compared with unirrigated, unsprayed plots, antitranspirant gave a grain yield benefit of 0.66 t ha–1. Further work is needed to validate the pollen viability mechanism in different climatic zones and with a wide range of cultivars

Applying sunflower oil to rapeseed plants reduces water loss

Background Hydrophobic polymers are used as antitranspirants to block stomata and reduce water loss from plants and thus drought stress, but the use of current commercial products is limited because they are expensive. Plant oils may be much cheaper hydrophobic polymers if they have similar efficacy to commercial antitranspirant products. Two experiments with pot-grown rapeseed plants were conducted to compare sunflower oil with the commercially-available antitranspirant di-1-p-menthene (DPM) for efficacy in reducing water loss, and to test for a linear response to increasing oil concentration. Results Sunflower oil at the same concentration as DPM (0.5%) was similar in efficacy in reducing the rate of water loss, measured as both rate of weight loss of the plant and rate of stomatal conductance decline. There was a linear response to increasing concentrations of oil, as found in previous research with DPM on rapeseed, with a slower rate of water loss the greater the concentration. Conclusion If other plant oils are equally or more effective in reducing water loss as sunflower oil, there may be potential for plant oils to be used as low-cost antitranspirants to reduce drought damage on large-scale commodity crops, and also by smallholder farmers in low-income countries using locally-produced plant oils

Wheat area expansion into northern higher latitudes and global food security

Wheat is an important crop for global food security, but it is unlikely that the upper end of future global food demand projections can be satisfied from improving wheat yield on the existing cropping area. Climate warming is, however, enabling wheat to be grown on previously uncropped land at higher northern latitudes. There are numerous problems with growing wheat in these regions, including perhaps most importantly release of greenhouse gases. Research and development of wheat production techniques which minimise environmental damage in high latitudes is needed

Hydraulic Redistribution from Wet to Drying Roots of Potatoes (Solanum tubersosum L.) During Partial Rootzone Drying

Hydraulic redistribution, redistribution of water upward or downward within a soil profile through roots as a consequence of root-soil water potential gradients, can be an important mechanism in transporting chemical signals (i.e. abscisic acid) to the shoot for stomatal closure or in maintaining the root system during dry periods of partial rootzone drying (PRD). PRD involves alternate irrigation to two sides of a plant root system. The study reported here investigated the occurrence and magnitude of hydraulic redistribution in glasshouse-grown potatoes (Solanum tuberosum L.) under PRD. Deuterium labelled water was applied to only one half of the root system to field capacity at tuber initiation. The roots from the drying side of the dual pot were extracted at 3, 6, 12, 18 and 24 h following watering by the dry sieving method. Water from the roots was extracted by azeotropic distillation and analysed for hydrogen isotope ratios. Hydraulic redistribution occurred the most at night when stomatal conductance was considerably lower and leaf water potential was higher (less negative). The magnitude of the redistributed water, however, did not exceed 3.5%, indicating limited water redistribution under PRD. The observed water redistribution would probably be of little significance for the survival of roots present in the upper drier portion of the soil under higher water demanding conditions but its role in sending the chemical signals to the shoot to conserve water by reducing transpiration would be of particular significance during drying periods of partial rootzone drying

Increasing the concentration of film antitranspirant increases yields of rapeseed under terminal drought by improving plant water status

Film antitranspirant (AT) can effectively reduce yield losses of rapeseed crops under drought by blocking stomata if applied at the critical stage. However, the physiological mechanism by which film AT mitigates drought damage remains unclear. To investigate the effect of different concentrations of AT from 1% to 3% on rapeseed yields and its components of rapeseed under terminal drought, we carried out two field experiments at two locations in the year 2021, using rain shelters to simulate terminal drought at Bird’s Nest (BN) and Flat Nook (FN). The study was conducted in a randomised complete block design with different concentrations of film AT (Vapor Gard, a.i., di-1-p-menthene) from 0% to 3% applied at the flowering stage of water-stressed rapeseed. Soil and plant water status, leaf gas exchange, seed yield and yield components, etc., were examined. Drought depressed leaf gas exchange and resulted in large yield losses. Aboveground biomass, seed yield, pod number and oil yield showed linear increases with AT concentrations consistently from both sites. With every 1% increase in concentration, seed yield was predicted to increase by 0.61 and 0.23 t ha−1 at BN and FN, respectively. The improvement in seed yield was strongly associated with pod number (R2 = 0.97 and 0.76, respectively; p < 0.001). Further, pod number and leaf relative water content were positively correlated, albeit with differences between the two sites. It was concluded that increasing concentrations can enhance yield benefits of film AT on rapeseed subjected to drought, and the greater yield from film AT appeared to be mediated through the improvement in leaf water status. As high concentrations of film AT are less cost-effective and conventional spraying methods only cover the adaxial surface, improving leaf coverage considering both sides of the leaf surface would help lower the cost and extend the commercial use of film AT

The potential of antitranspirants in drought management of arable crops: a review

About 80 % of global farmland is under rain-fed conditions and most of it is prone to drought, which limits crop productivity. Due to climate change, drought will become more frequent and severe, threatening world food security. Antitranspirants, materials that reduce transpiration, could potentially result in greater food production by realising more of a crop’s potential yield during drought. Despite antitranspirants reducing photosynthesis, research has shown that they can mitigate drought stress and increase grain yield. Although this paper is not restricted to specific years, part of it is a systematic review of 173 original research articles published between 2009 and 2018. Overall, the analysis suggests that interest in the potential of antitranspirants is growing. One major achievement in antitranspirant research during the past decade was establishing the optimal timing of application of the substances, which is linked to reproductive processes most vulnerable to drought. Despite research evidence of the efficacy of antitranspirants in ameliorating drought stress, they are not widely used for commercial arable crop production. However, in fruit horticulture, products with antitranspirant effects are already being used commercially for various non-antitranspirant purposes. More recent research shows that with knowledge of a crop's growth stage and soil moisture, antitranspirants can be a valuable option for managing drought impacts on yield in arable crops

Rising CO2 from historical concentrations enhances the physiological performance of Brassica napus seedlings under optimal water supply but not under reduced water availability

The productivity of many important crops is significantly threatened by water shortage, and the elevated atmospheric CO2 can significantly interact with physiological processes and crop responses to drought. We examined the effects of three different CO2 concentrations (historical ~300 ppm, ambient ~400 ppm and elevated ~700 ppm) on physiological traits of oilseed rape (Brassica napus L.) seedlings subjected to well-watered and reduced water availability. Our data show (1) that, as expected, increasing CO2 level positively modulates leaf photosynthetic traits, leaf water-use efficiency and growth under non-stressed conditions, although a pronounced acclimation of photosynthesis to elevated CO2 occurred; (2) that the predicted elevated CO2 concentration does not reduce total evapotranspiration under drought when compared with present (400 ppm) and historical (300 ppm) concentrations because of a larger leaf area that does not buffer transpiration; and (3) that accordingly, the physiological traits analysed decreased similarly under stress for all CO2 concentrations. Our data support the hypothesis that increasing CO2 concentrations may not significantly counteract the negative effect of increasing drought intensity on Brassica napus performance