Induced leaf intercellular CO₂, photosynthesis, potassium and nitrate retention and strawberry early fruit formation under macronutrient limitation

The Responses of Sucrose Metabolism and Carbon Translocation in Tomato Seedlings under Different Light Spectra

Light plays a dominant role in the biosynthesis and accumulation of photosynthetic products. However, the metabolism and translocation of photosynthetic products in plants under different light spectra remain elusive. In this study, tomato (Solanum lycopersicum L.) seedlings were treated with different light spectra delivered by light-emitting diodes (LEDs) with the same photosynthetic photon flux density at 300 μmol m-2 s-1, including monochromatic red (660 nm, R), blue (450 nm, B), sun-like white (W, 380-780 nm), or a combination of R and B lights (R:B = 1:1, RB). Compared with W, the biomass distribution ratio for leaves under R, B, and RB decreased by 5.01-9.53%, while the ratio for stems and roots increased by 3.71-6.92% and 0.14-2.81%, respectively. The photosynthetic carbon distribution expressed as 13C enrichment was higher in stems and roots under RB and R, while B led to more 13C transported from leaves and enriched in stems when compared with W. Meanwhile, RB led to significant increases in the activities of phosphate synthase (SPS), sucrose synthase (SS), vacuolar acid invertase (VI), and neutral invertase (NI). The R was more efficient in increasing the activity of SPS and SS, while B was more effective in promoting the activity of VI and NI. The transcript levels of SPS, SS3, NI6, and VI were upregulated under R, B, and RB. However, the transcript patterns of SPS, SS3, NI6, and VI were not consistent with the changes in their encoded enzymes, especially the transcript patterns of SPS and SS3. Our study suggests that the red- and blue-light-induced long-distance and short-distance transport of photosynthetic products in plants, respectively, might result from different regulation of sucrose-metabolizing enzymes from transcriptional and post-transcriptional levels.

Leaf cell membrane stability-based mechanisms of zinc nutrition in mitigating salinity stress in rice

Excess salt affects about 955 million ha of arable land worldwide, and 49% of agricultural land is Zn-deficient. Soil salinity and zinc deficiency can intensify plant abiotic stress. The mechanisms by which Zn can mitigate salinity effects on plant functions are not well understood. We conducted an experiment to determine how Zn and salinity effects on rice plant retention of Zn, K⁺ and the salt ion Na⁺ affect chlorophyll formation, leaf cell membrane stability and grain yield. We examined the mechanisms of Zn nutrition in mitigating salinity stress by examining plant physiology and nutrition. We used native Zn-deficient soils (control), four salinity (EC) and Zn treatments - Zn 10 mg·kg^-1 (Zn₁₀ ), EC 5 dS·m^-1 (EC₅ ), Zn₁₀ +EC₅ and Zn₁₅ +EC₅ , a coarse rice (KS-282) and a fine rice (Basmati-515) in the study. Our results showed that Zn alone (Zn₁₀ ) significantly increased rice tolerance to salinity stress by promoting Zn/K⁺ retention, inhibiting plant Na⁺ uptake and enhancing leaf cell membrane stability and chlorophyll formation in both rice cultivars in native alkaline, Zn-deficient soils (P < 0.05). Further, under the salinity treatment (EC₅ ), Zn inputs (10-15 mg·kg^-1 ) could also significantly promote rice plant Zn/K⁺ retention and reduce plant Na⁺ uptake, and thus increased leaf cell membrane stability and grain yield. Coarse rice was more salinity-tolerant than fine rice, having significantly higher Zn/K⁺ nutrient retention. The mechanistic basis of Zn nutrition in mitigating salinity impacts was through promoting plant Zn/K⁺ uptake and inhibiting plant Na⁺ uptake, which could result in increased plant physiological vigour, leaf cell membrane stability and rice productivity.