Regulation of non-structural carbohydrates (NSCs) are important for plants in response to submergence. In this study, the difference in non-structural carbohydrates in relation with shoot elongation between Sub1A and non-Sub1A rice genotypes was investigated. Two rice genotypes, namely Inpari30 (Sub1A genotype) and IR72442 (non-Sub1A genotype), were submerged completely for 6 days and re-aerated by lowering water level up to stem base for 6 days of post submergence. In addition, non-submerged plants (control) was treated with water level up to stem base during the experiment. Photosynthesis rate decreased in both submerged Inpari30 and IR72442 genotypes 71% and 96% lower than their control, respectively. Submerged IR72442 declined Fv/Fm 15.6% lowest than its control and both control and submerged Inpari30. Investigation of the distribution of starch and soluble sugar content in plant organs suggested that shoot elongation of non-Sub1A genotype led to starch and sugar consumption that distributed faster to the new developed organ during submergence. In contrast, Sub1A genotype of Inpari30, which did not exhibit shoot elongation and showed slower NSCs distribution during submergence, performed better on post submergence by maintaining NSCs and distributing to the new developed organ faster than IR72442. These results suggest that Sub1A genotype managed elongation and NSCs during submergence more efficiently than non-Sub1A genotype.

Seed priming refers to seed enhancement methods that stimulate seed metabolism. This study evaluated the genetic diversity of hydro priming efficacy in 27 different genotypes of rice under dry to wet soil moisture conditions. The genotypes included 21 genotypes of Oryza sativa, five genotypes of Oryza glaberrima, and one genotype of NERICA (New Rice for Africa). The treated rice seeds were sown in plastic boxes under four soil moisture conditions (5%, 10%, 15%, and 20% (w/w)). The genotypes were categorized into six groups based on growth parameters using hierarchical cluster analysis. Furthermore, emergence properties were investigated by using principal component analysis based on the mean emergence time of control and primed seeds. Seed priming enhanced growth performance under the moderate dry conditions of 10% and 15% soil moisture. Meanwhile, priming efficacy was low in water stress conditions of 5% and 20% soil moisture. There were wide-ranging genotypic differences of priming efficacy under 20% soil moisture condition. Our findings indicate that the anaerobic-tolerant genotypes tend to exhibit priming efficacy under high soil moisture conditions. Furthermore, one group included all upland genotypes of Oryza sativa. This group originally adapted to 10% and 15% of dry conditions, and seed priming improved their features greatly.

Environmental responses of stomatal conductance (gs) as basic information for a photosynthesis-transpiration-coupled model have been increasing under global warming. This study identified the impact of gs behavior under different soil water statuses and temperatures in rice, maize, millet, and sorghum. The experiments consisted of various soil moisture statuses from flooding to drying and combination of soil moisture status and temperature. There was a reduction in shoot biomass of maize and sorghum caused by decreasing of gs, photosynthesis (A), and transpiration (E) in early imposed waterlogging without dependent temperature, whereas millet and rice were dependent on temperature variation. The effect of gradual soil drying, gs, A, and E of maize, millet, and sorghum were caused by low temperature, except rice. The impact of the combination of various soil water statuses and temperatures on gs is important for the trade-off between A and E, and consequently shoot biomass. However, we discovered that an ability to sustain gs is essential for photo assimilation and maintaining leaf temperature through evapotranspiration for biomass production, a mechanism of crop avoidance in variable soil water status and temperature.

Hydropriming rice seeds effectively improve the germination percentage, shortens the germination period, and promotes seedling growth. The impact of seed hydropriming is to speed up growth under dry soil conditions, thereby avoiding drought damage. This study analyzes the effect of hydropriming on morpho-physiological changes in the water uptake of rice seeds using “Kasalath” and “Nipponbare” under water-deficit conditions. Upon exposure to osmotic stress, both varieties showed delays in the time to reach germination. In addition, all germination phases exhibited reductions in the activity of alpha-amylase and total soluble sugar by osmotic stress; however, in all germination phases of the hydroprimed seeds, the activity and contents of those were significantly increased, resulting in increased size of the coleoptile, plumule, and radicle. In hydroprimed seeds, “Kasalath” was superior to “Nipponbare” in the ratio of the water-deficit-to-well-watered conditions for all traits related to germination, which may have been attributable to hydropriming having a greater effect on “Kasalath”. Interestingly, Primed “Kasalath” had a lower level of α-amylase, despite the having a higher content of total soluble sugars than primed “Nipponbare”.

Flooding and drought are major causes of reductions in crop productivity. Root distribution indicates crop adaptation to water stress. Therefore, we aimed to identify crop roots response based on root distribution under various soil conditions. The root distribution of four crops—maize, millet, sorghum, and rice—was evaluated under continuous soil waterlogging (CSW), moderate soil moisture (MSM), and gradual soil drying (GSD) conditions. Roots extended largely to the shallow soil layer in CSW and grew longer to the deeper soil layer in GSD in maize and sorghum. GSD tended to promote the root and shoot biomass across soil moisture status regardless of the crop species. The change of specific root density in rice and millet was small compared with maize and sorghum between different soil moisture statuses. Crop response in shoot and root biomass to various soil moisture status was highest in maize and lowest in rice among the tested crops as per the regression coefficient. Thus, we describe different root distributions associated with crop plasticity, which signify root spread changes, depending on soil water conditions in different crop genotypes as well as root distributions that vary depending on crop adaptation from anaerobic to aerobic conditions.