NaCl-altered oxygen flux profiles and H+-ATPase activity in roots of two contrasting poplar species

Advances in deciphering the mechanisms of salt tolerance in Maize

Maize (Zea mays L.) is a vital crop worldwide, serving as a cornerstone for food security, livestock feed, and biofuel production. However, its cultivation is increasingly jeopardized by environmental challenges, notably soil salinization, which severely constrains growth, yield, and quality. To combat salinity stress, maize employs an array of adaptive mechanisms, including enhanced antioxidant enzyme activity and modulated plant hormone levels, which work synergistically to maintain reactive oxygen species (ROS) balance and ion homeostasis. This review explores the intricate interactions among ROS, antioxidant systems, plant hormones, and ion regulation in maize under salt stress, providing a comprehensive understanding of the physiological and molecular basis of its tolerance. By elucidating these mechanisms, this study contributes to the development of salt-tolerant maize varieties and informs innovative strategies to sustain agricultural productivity under adverse environmental conditions, offering significant theoretical insights into plant stress biology and practical solutions for achieving sustainable agriculture amidst global climate challenges.

Effect of NaCl on ammonium and nitrate uptake and transport in salt-tolerant and salt-sensitive poplars

Nitrogen (N) plays an important role in mitigating salt stress in tree species. We investigate the genotypic differences in the uptake of ammonium (NH4+) and nitrate (NO3-) and the importance for salt tolerance in two contrasting poplars, salt-tolerant Populus euphratica Oliv. and salt-sensitive P. simonii × (P. pyramidalis ×Salix matsudana) (P. popularis cv. 35-44, P. popularis). Total N content, growth and photosynthesis were significantly reduced in P. popularis after 7 days of exposure to NaCl (100 mM) supplied with 1 mM NH4+ and 1 mM NO3-, while the salt effects were not pronounced in P. euphratica. The 15NH4+ trace and root flux profiles showed that salt-stressed poplars retained ammonium uptake, which was related to the upregulation of ammonium transporters (AMTs) in roots, as two of the four AMTs tested significantly increased in salt-stressed P. euphratica (i.e., AMT1.2, 2.1) and P. popularis (i.e., AMT1.1, 1.6). It should be noted that P. euphratica differs from salt-sensitive poplar in the maintenance of NO3- under salinity. 15NO3- tracing and root flux profiles showed that P. euphratica maintained nitrate uptake and transport, while the capacity to uptake NO3- was limited in salt-sensitive P. popularis. Salt increased the transcription of nitrate transporters (NRTs), NRT1.1, 1.2, 2.4, 3.1, in P. euphratica, while P. popularis showed a decrease in the transcripts of NRT1.1, 2.4, 3.1 after 7 days of salt stress. Furthermore, salt-stimulated transcription of plasmalemma H+-ATPases (HAs), HA2, HA4 and HA11 contributed to H+-pump activation and NO3- uptake in P. euphratica. However, salt stimulation of HAs was less pronounced in P. popularis, where a decrease in HA2 transcripts was observed in the stressed roots. We conclude that the salinity-decreased transcripts of NRTs and HAs reduced the ability to uptake NO3- in P. popularis, resulting in limited nitrogen supply. In comparison, P. euphratica maintains NH4+ and NO3- supply, mitigating the negative effects of salt stress.