Background and aims Determination of sodium (Na), potassium (K), and chloride (Cl) content in plant tissue is required for research related to salinity resistance in plants. Standard methods are available to extract these elements from dried plant material, but these methods are often costly, relatively dangerous, or time consuming. Many authors modify extraction methods substantially without proof of comparability across methods. Methods Here, dried tissues of two varieties of rice and three varieties of sweet potato subjected to salt stress were extracted for Na and K using six different extraction methods (1–6) and for Cl using three Cl‐free extraction methods (2, 4, 5) for Cl: (1) the VDLUFA standard method, consisting of ashing, and heat extraction in hydrochloric acid (HCl), (2) hot water pressure extraction via autoclave, (3) extraction with 1 M HCl overnight, (4) hot water extraction at 90°C for 1 h, (5) acetic acid extraction in hot 1 M acetic acid for 2 h, and (6) extraction with a microwave using nitric acid. Na and K were determined via flame photometer and Cl via automated flow analysis. Results Na and K concentrations varied little among different extraction methods as compared to the VDLUFA standard method, and for Cl, all extractions resulted in similar tissue Cl concentrations. Conclusions Ultimately, the choice of extraction method depends on the instrumentation and lab equipment necessary, available budget, the available amount of sample, and time constraints which should be decided according to the experiment. For reasons of comparability among publications, methods applied should be clearly described since results vary depending on the method chosen.

In the Vietnamese Mekong Delta (VMD), alternate wetting and drying (AWD) in rice (Oryza sativa L.) production during the dry season has the potential to reduce greenhouse gas emission and freshwater use. However, its effect on yield compared with continuously flooded systems can vary. To evaluate the effect of AWD on yield and yield‐forming processes on genotypes commonly grown in the VMD, field trials over two consecutive dry seasons were conducted at the Loc Troi Group's agricultural research station in the VMD. We observed a significant yield reduction, 7% on average, across all varieties grown under AWD. Analysis of yield components showed that under AWD, genotypes on average produced more tillers, but fewer spikelets, suffered greater spikelet sterility and had a lower 1000 grain weight. The size of this effect differed between dry seasons. Accordingly, we were able to identify and characterize genotypes better suited to AWD. We also could relate shifts in sink‐source relationships to the overlap of drying events and key phenological stages other than flowering. Our study shows how successful implementation of AWD requires adaptation to both environment and genotype.

Alternate wetting and drying irrigation (AWD) has been shown to decrease water use and trace gas emissions from paddy fields. Whereas genotypic water use shows little variation, it has been shown that rice varieties differ in the magnitude of their methane emissions. Management and variety‐related emission factors have been proposed for modelling the impact of paddy production on climate change; however, the magnitude of a potential reduction in greenhouse gas emissions by changing varieties has not yet been fully assessed. AWD has been shown to affect genotypic yields and high‐yielding varieties suffer the greatest loss when grown under AWD. The highest yielding varieties may not have the highest methane emissions; thus, a potential yield loss could be compensated by a larger reduction in methane emissions. However, AWD can only be implemented under full control of irrigation water, leaving the rainy seasons with little scope to reduce methane emissions from paddy fields. Employing low‐emitting varieties during the rainy season may be an option to reduce methane emissions but may compromise farmers’ income if such varieties perform less well than the current standard. Methane emissions and rice yields were determined in field trials over two consecutive winter/spring seasons with continuously flooded and AWD irrigation treatments for 20 lowland rice varieties in the Mekong Delta of Vietnam. Based on the results, this paper investigates the magnitude of methane savings through varietal choice for both AWD and continuous flooding in relation to genotypic yields and explores potential options for compensating farmers’ mitigation efforts.

Accurate measurement of leaf transpiration (E) and related stomatal conductance (g s ) is fundamental to understanding plant energy dynamics and water relations at all scales, from pot to field (Pearcy et al., 2000). It is inextricably linked to photosynthesis as E and carbon assimilation share the same route in their way out of and into the leaf (Stanhill, 1986). It is a major component of the hydrological cycle and is a useful reflection of the adjustments of a plant to the surrounding environment. Available methods to measure E in herbaceous plants include: (1) porometers or infrared gas analyzers (IRGAs) that measure either at the single leaf or whole-plant level; (2) lysimeters that measure intact soil column weight loss (usually combining E and evaporation of individual plants or smaller communities) (Bello & Van Rensburg, 2017); (3) Eddy covariance; and (4) remote sensing methods encompassing landscape and regional scales with satellite image analysis (Talsma, 2018). However, measurements on individual leaves using hand-held IRGAs/porometers are unable to capture whole plant heterogeneity arising from differences in leaf age, leaf position, plant architecture, as well as temperature and boundary layer (Pearcy et al., 2000). Whole-plant chambers linked to an IRGA, on the other hand, are costly and replication is timeconsuming (Ryan et al., 2016). In both cases, it is difficult to relate cuvette to field conditions (Tardieu & Simonneau, 1998). Whereas