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The use of slow-release fertilizers and seed-fertilizers cause localized highammonium (NH4+) environments in agricultural fields, adversely affecting wheat growth and development and delaying its yield. Thus, it is important to investigate the physiological responses of wheat and its tolerance to NH4+ stress to improve the adaptation of wheat to high NH4+ environments. In this study, the physiological mechanisms of ammonium tolerance in wheat (Triticum aestivum) were investigated in depth by comparative analysis of two cultivars: NH4+-tolerant Xumai25 and NH4+-sensitive Yangmai20. Cultivation under hydroponic conditions with high NH4+ (5 mM NH4+, AN) and nitrate (5 mM NO3-, NN), as control, provided insights into the nuanced responses of both cultivars. Compared to Yangmai20, Xumai25 displayed a comparatively lesser sensitivity to NH4+ stress, as evident by a less pronounced reduction in dry plant biomass and a milder adverse impact on root morphology. Despite similarities in NH4+ efflux and the expression levels of TaAMT1.1 and TaAMT1.2 between the two cultivars, Xumai25 exhibited higher NH4+ influx, while maintaining a lower free NH4+ concentration in the roots. Furthermore, Xumai25 showed a more pronounced increase in the levels of free amino acids, including asparagine, glutamine, and aspartate, suggesting a superior NH4+ assimilation capacity under NH4+ stress compared to Yangmai20. Additionally, the enhanced transcriptional regulation of vacuolar glucose transporter and glucose metabolism under NH4+ stress in Xumai25 contributed to an enhanced carbon skeleton supply, particularly of 2-oxoglutarate and pyruvate. Taken together, our results demonstrate that the NH4+ tolerance of Xumai25 is intricately linked to enhanced glucose metabolism and optimized glucose transport, which contributes to the robust NH4+ assimilation capacity. [ABSTRACT FROM AUTHOR]

The use of slow-release fertilizers and seed-fertilizers cause localized high-ammonium (NH4+) environments in agricultural fields, adversely affecting wheat growth and development and delaying its yield. Thus, it is important to investigate the physiological responses of wheat and its tolerance to NH4+ stress to improve the adaptation of wheat to high NH4+ environments. In this study, the physiological mechanisms of ammonium tolerance in wheat (Triticum aestivum) were investigated in depth by comparative analysis of two cultivars: NH4+-tolerant Xumai25 and NH4+-sensitive Yangmai20. Cultivation under hydroponic conditions with high NH4+ (5 mM NH4+, AN) and nitrate (5 mM NO3-, NN), as control, provided insights into the nuanced responses of both cultivars. Compared to Yangmai20, Xumai25 displayed a comparatively lesser sensitivity to NH4+ stress, as evident by a less pronounced reduction in dry plant biomass and a milder adverse impact on root morphology. Despite similarities in NH4+ efflux and the expression levels of TaAMT1.1 and TaAMT1.2 between the two cultivars, Xumai25 exhibited higher NH4+ influx, while maintaining a lower free NH4+ concentration in the roots. Furthermore, Xumai25 showed a more pronounced increase in the levels of free amino acids, including asparagine, glutamine, and aspartate, suggesting a superior NH4+ assimilation capacity under NH4+ stress compared to Yangmai20. Additionally, the enhanced transcriptional regulation of vacuolar glucose transporter and glucose metabolism under NH4+ stress in Xumai25 contributed to an enhanced carbon skeleton supply, particularly of 2-oxoglutarate and pyruvate. Taken together, our results demonstrate that the NH4+ tolerance of Xumai25 is intricately linked to enhanced glucose metabolism and optimized glucose transport, which contributes to the robust NH4+ assimilation capacity.

Soil acidification often occurs when the concentration of ammonium (NH4+) in soil rises, such as that observed in farmland. Both soil acidification and excess NH4+ have serious adverse effects on crop growth and food production. However, we still do not know which of these two inhibitors has a greater impact on the growth of crops, and the degree of their inhibitory effect on crop growth have not been accurately evaluated. 31 wheat cultivars originating in various areas of China were planted under 5 mM sole NH4+ (ammonium nitrogen, AN) or nitrate nitrogen in combined with two pH levels resembling acidified conditions (5.0 and 6.5). The results showed that the shoots and roots biomass were severely reduced by AN in both and these reduction effects were strengthened by a low medium pH. The concentration of free NH4+ and amino acids, the glutamine synthetase activity were significantly higher, but the total soluble sugar content was reduced under NH4+ conditions, and the glutamine synthetase activity was reduced by a low medium pH. Cultivar variance was responsible for the largest proportion of the total variance in plant dry weight, leaf area, nodal root number, total root length and root volume; the nitrogen (N) form explains most of the variation in N and C metabolism; the effects of pH were the greatest for plant height and root average diameter. So, soil acidification and excess NH4+ would cause different degrees of inhibition effects on different plant tissues. The findings are expected to be useful for applying effective strategies for reducing NH4+ stress in the field. [ABSTRACT FROM AUTHOR]

Soil acidification often occurs when the concentration of ammonium (NH4+) in soil rises, such as that observed in farmland. Both soil acidification and excess NH4+ have serious adverse effects on crop growth and food production. However, we still do not know which of these two inhibitors has a greater impact on the growth of crops, and the degree of their inhibitory effect on crop growth have not been accurately evaluated. 31 wheat cultivars originating in various areas of China were planted under 5 mM sole NH4+ (ammonium nitrogen, AN) or nitrate nitrogen in combined with two pH levels resembling acidified conditions (5.0 and 6.5). The results showed that the shoots and roots biomass were severely reduced by AN in both and these reduction effects were strengthened by a low medium pH. The concentration of free NH4+ and amino acids, the glutamine synthetase activity were significantly higher, but the total soluble sugar content was reduced under NH4+ conditions, and the glutamine synthetase activity was reduced by a low medium pH. Cultivar variance was responsible for the largest proportion of the total variance in plant dry weight, leaf area, nodal root number, total root length and root volume; the nitrogen (N) form explains most of the variation in N and C metabolism; the effects of pH were the greatest for plant height and root average diameter. So, soil acidification and excess NH4+ would cause different degrees of inhibition effects on different plant tissues. The findings are expected to be useful for applying effective strategies for reducing NH4+ stress in the field.

Polyamine(s) (PA, PAs), a sort of N-containing and polycationic compound synthesized in almost all organisms, has been recently paid considerable attention due to its multifarious actions in the potent modulation of plant growth, development, and response to abiotic/biotic stresses. PAs in cells/tissues occur mainly in free or (non- or) conjugated forms by binding to various molecules including DNA/RNA, proteins, and (membrane-)phospholipids, thus regulating diverse molecular and cellular processes as shown mostly in animals. Although many studies have reported that an increase in internal PA may be beneficial to plant growth under abiotic conditions, leading to a suggestion of improving plant stress adaption by the elevation of endogenous PA via supply or molecular engineering of its biosynthesis, such achievements focus mainly on PA homeostasis/metabolism rather than PA-mediated molecular/cellular signaling cascades. In this study, to advance our understanding of PA biological actions important for plant stress acclimation, we gathered some significant research data to succinctly describe and discuss, in general, PA synthesis/catabolism, as well as PA as an internal ameliorator to regulate stress adaptions. Particularly, for the recently uncovered phenomenon of urea-antagonized NH4+-stress, from a molecular and physiological perspective, we rationally proposed the possibility of the existence of PA-facilitated signal transduction pathways in plant tolerance to NH4+-stress. This may be a more interesting issue for in-depth understanding of PA-involved growth acclimation to miscellaneous stresses in future studies. [ABSTRACT FROM AUTHOR]

Polyamine(s) (PA, PAs), a sort of N-containing and polycationic compound synthesized in almost all organisms, has been recently paid considerable attention due to its multifarious actions in the potent modulation of plant growth, development, and response to abiotic/biotic stresses. PAs in cells/tissues occur mainly in free or (non- or) conjugated forms by binding to various molecules including DNA/RNA, proteins, and (membrane-)phospholipids, thus regulating diverse molecular and cellular processes as shown mostly in animals. Although many studies have reported that an increase in internal PA may be beneficial to plant growth under abiotic conditions, leading to a suggestion of improving plant stress adaption by the elevation of endogenous PA via supply or molecular engineering of its biosynthesis, such achievements focus mainly on PA homeostasis/metabolism rather than PA-mediated molecular/cellular signaling cascades. In this study, to advance our understanding of PA biological actions important for plant stress acclimation, we gathered some significant research data to succinctly describe and discuss, in general, PA synthesis/catabolism, as well as PA as an internal ameliorator to regulate stress adaptions. Particularly, for the recently uncovered phenomenon of urea-antagonized NH4+-stress, from a molecular and physiological perspective, we rationally proposed the possibility of the existence of PA-facilitated signal transduction pathways in plant tolerance to NH4+-stress. This may be a more interesting issue for in-depth understanding of PA-involved growth acclimation to miscellaneous stresses in future studies.