Salinity may strongly influence the interaction between plant roots and surrounding soil, but this has been poorly studied for sodium sulfate (Na₂SO₄). The aim of this study was to investigate the effect of sodium chloride (NaCl) and Na₂SO₄ salinities on the soil chemical properties as well as rice physiological- and yield-related parameters of two contrasted cultivars (V14 (salt-sensitive) and Pokkali (salt-resistant)). Pot experiments were conducted using soil and electrolyte solutions, namely NaCl and Na₂SO₄, inducing two electrical conductivity levels (EC: 5 or 10 dS m⁻¹) of the soil solutions. The control treatment was water with salt-free tap water. Our results showed that soil pH increased under Na₂SO₄ salinity, while soil EC increased as the level of saline stress increased. Salinity induced an increase in Na⁺ concentrations on solid soil complex and in soil solution. NaCl reduced the stomatal density in salt-sensitive cultivar. The total protein contents in rice grain were higher in V14 than in Pokkali cultivar. Saline stress significantly affected all yield-related parameters and NaCl was more toxic than Na₂SO₄ for most of the studied parameters. Pokkali exhibited a higher tolerance to saline stress than V14, whatever the considered type of salt. It is concluded that different types of salts differently influence soil properties and plant responses and that those differences partly depend on the salt-resistance level of the considered cultivar.

To elucidate the comparative effect of chloride and sulfate salinities on photosynthesis and yield components in rice, plants of Oryza sativa (cv. I Kong Pao (salt-sensitive)) were exposed in nutrient solutions to 20 mM Na₂SO₄ or 40 mM NaCl (electrical conductivity of c.a. 4.30 dS m⁻¹ for both solutions) from seedlings to maturity stage. Both types of salt induced a strong decrease in net photosynthesis (A_N) at the seedling and tillering stages, while the intercellular CO₂ concentrations (Ci) remained unaffected. Instantaneous transpiration (E) and stomatal conductance (g_s) decreased at the tillering and seedling stages, respectively, only in plants exposed to NaCl. Chloride salinity also strongly decreased photosynthetic pigments, while no impact was detected in response to Na₂SO₄. All yield-related parameters were affected by salinities, but NaCl was significantly more deleterious than Na₂SO₄ for the mean number of tillers produced per plant, spikelets sterility and non-viable pollen percentage. In contrast, both types of salinity similarly impacted the percentage of fertile tillers and 1000-grain weight. At the grain level, more than 90% of toxic ions (Na⁺, excess of Cl⁻ and S⁶⁺) accumulated in the hulls, thus preserving the internal part of the caryopses from toxic ion injuries.

We analyzed the expression of genes coding for Na⁺ transporters (OsHKT1.5, OsHKT1.1, OsSOS1, OsSOS2, OsNHX1, OsNHX2), Cl^- transporter (OsNRT1, OsCLC, OsCCC1) and gene coding for the transcription factor DREB (OsDREB2) involved in response to desiccation in two cultivars of O. glaberrrima differing in salt-resistance (salt-tolerant cultivar (TOG5307) and salt-sensitive (TOG 5949)) exposed to NaCl, PEG or both agents present simultaneously. Seedlings were grown in iso-osmotic nutrient solution (Ψs = -0.47±0.02 MPa) containing PEG 6,000 12.9% (water stress), NaCl 75 mM (salt stress) and PEG 6.4% + NaCl 37.5 mM (MIX-treatment) during 1 and 7 days. Plants were analyzed for gene expression, mineral nutrients, and photosynthetic-related parameters. Na⁺ and Cl^- accumulations in salt-treated plants were lower in roots and shoots of TOG5307 comparatively to TOG5949 while water content decreased in TOG5307. TOG5307 exhibited tolerance to water stress and maintained higher net photosynthesis and water use efficiency than TOG5949 in response to all treatments, but was less efficient for osmotic adjustment. Dehydration tolerance of TOG5307 involves a higher OsDREB2 expression. TOG5307 also exhibited a higher OsSOS1, OsSOS2, OsNHX1 and OsNHX2 expression than TOG5949 in response to salinity. OsHKT1.5 was slightly induced in the shoot. OsHKT1.1 was recorded in the shoots but remained undetectable in the roots. Chloride and sodium accumulations were strongly reduced in the shoots when PEG was present. Salinity resistance in Oryza glaberrima implies tolerance to dehydration as well as complementary strategies of Na⁺ exclusion through the SOS system and Na⁺ tolerance through vacuolar sequestration.

Flexible developmental programs enable plants to customize their organ size and cellular composition. In leaves of eudicots, the stomatal lineage produces two essential cell types, stomata and pavement cells, and plants can adjust the total numbers and ratios of these cell types in response to external cues. Central to this flexibility is the stomatal lineage-initiating transcription factor, SPEECHLESS (SPCH). Here we explore the mechanisms underlying the involvement of SPCH in environmental response. Using multiplexed CRISPR/Cas9 editing of SlSPCH cis-regulatory sequences in tomato, we identified variants with altered stomatal development responses to drought, light and temperature cues. By creating and live-cell tracking translational reporters of SlSPCH and its paralogues SlMUTE and SlFAMA, we revealed the corresponding cellular events that lead to the environmental change-driven responses in stomatal production and leaf form. Plants bearing the novel reporters and SlSPCH variants are powerful resources for fundamental and applied studies of tomato resilience in response to climate change.

Waterlogging constrains terrestrial plants by limiting gas diffusion and altering the hydraulic and chemical environment of roots. Yet it remains unclear which whole-plant responses arise from oxygen limitation alone and which require the broader physical context of excess water. Using high-resolution gravimetric lysimetry in tomato, we compared N₂-induced hypoxia under near-field-capacity conditions with root-zone waterlogging. N₂ injection reduced root-zone O₂ from approximately 18%-19% to below 1% and altered pH, redox potential, and mineral relations, but whole-plant transpiration declined only after sustained exposure. Waterlogging caused a faster, genotype-dependent transpiration decline in M82, IL11-4, and IL8-1. Adventitious-root emergence at the soil-air interface coincided with transient partial recovery of transpiration, whereas stronger adventitious-root development occurred in plants with larger transpiration losses. The renewed decline in transpiration after drainage was consistent with a partial contribution of surface-associated adventitious roots, although restoration of drainage also altered root-zone aeration, water availability, and primary-root conditions and therefore did not isolate their specific contribution. Together, the distinct response kinetics and root phenotypes show that rapid N₂-induced hypoxia did not reproduce the full waterlogging response. Adventitious roots were induced most strongly under severe stress and were temporally associated with partial, but not complete, recovery of whole-plant transpiration.