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Optimizing tillage practices to improve crop yield and crop water productivity (CWP) is essential for promoting sustainable dryland agriculture. This meta-analysis used the water supply during the growing season (WS, total soil water storage at sowing time, and growing-season precipitation) instead of mean annual precipitation (MAP), to assess the effects of different tillage practices on the yield and CWP of winter wheat and spring maize in northern China. The results showed that WS had a stronger correlation with crop yield than MAP, especially for winter wheat. Compared with conventional tillage, no-tillage combined with straw mulching (SM) increased winter yield by 36.56 % and CWP by 17.93 % when WS ≤ 650 mm, and subsoiling tillage increased winter wheat yield by 21.17 % and CWP by 9.29 % in winter wheat yield when WS > 650 mm. SM and subsoiling tillage performed better in regions with higher mean annual temperature (MAT) than that with lower MAT. For spring maize, no tillage, no-tillage combined with plastic film mulching (PM), subsoiling tillage and rotary tillage significantly increased yield and CWP under different WS conditions and the highest effect was showed in PM under higher WS condition; meanwhile, PM and subsoiling tillage performed good under various temperature conditions, while rotary tillage performed better in areas with lower temperature. Thus, the recommended tillage practice for spring maize is PM in northeast China, and subsoiling tillage in north-central and northwest China; for winter wheat, subsoiling tillage is recommended for north-central China, and SM is recommended for northwest China. Taken together, our results indicate that it is more accurate to use WS rather than the MAP to evaluate appropriate tillage practices in drylands. Furthermore, WS can also replace MAP for yield estimation and prediction.

The study of crop response to soil salinity has traditionally focused on the effects of varying salt concentrations, with less attention given to the methodologies of salt application. This research aimed to elucidate the differential impacts of two distinct salinity exposure methods on the photosynthetic characteristics of rice. Plants subjected to a gradual increase in salinity experience salt stress, whereas those immediately exposed to high salinity levels encounter a salt shock condition. Our findings revealed that rice plants accumulated comparable levels of shoot Na+ under both salt stress and salt shock at 4 and 10 days after the onset of stress. No significant differences were observed in the steady-state photosynthetic rate and electron transport rate (ETR). In contrast, salt stress markedly reduced the relative variable fluorescence at the ‘J’ step (Vj), thereby enhancing the probability of an exciton transferring an electron beyond the primary quinone electron acceptor (QA−) (ΨEo). This led to a notable increase in the activity of leaf photosystem II (PSII), as evidenced by the Performance Index on absorption basis (PIabs), which was twice as high as that of the control group. This mechanism is believed to facilitate the activation of alternative metabolic pathways. Additionally, kinetic measurements of light potential indicated that salt stress improved the initial induction of ETR after a brief exposure to high photosynthetically active radiation (PAR) compared to the control. This effect was not observed in the salt shock treatment group. Our results suggest that plants exhibit distinct physiological responses to salt stress versus salt shock, and the potential positive influence on leaf photosynthetic activity during salt stress may have been previously underestimated.

Abstract Background Salinity stress is an environmental constraint that normally develops concurrently under field conditions, resulting in drastic limitation of rice plant growth and grain productivity. The objective of this study was to explore the alleviating effects of NaCl pre-treatment on rice seedlings as well as the salt tolerance mechanisms by evaluating morph-physiological traits. Results Variety Huanghuazhan, either soaked in distilled water or 25 mg/L Prohexadione calcium (Pro-Ca), were first hardened with varying concentrations of NaCl solutions (0 and 50 mM NaCl), and then subjected to varying degrees of salt stress (0 and 100 mM NaCl), indicated by S0, S1, S2 and S3, respectively. Growth analysis suggested that NaCl-pretreatment improved the root/shoot ratio in water-soaked rice plant at DAP 0. Data related to the reaction center density, photosynthetic electron transport efficiency, trapping efficiency were compared before (CK) using performance Index (PIabs). Compared to S2 (Pro-Ca-S2) treatment, PIabs did not show any difference with plants pre-treated with NaCl (S3 or Pro-Ca-S3). Rather than PIabs, significant difference was found in photosynthetic electron transport efficiency (ΨEo). The ΨEo value in Pro-S2 was significantly lowered as compared to Pro-S3 treatment at DAP 7, and the decrease rate was about 6.5%. Correlation analysis indicated leaf PIabs was weak correlated with plant biomass while the quantum yield for reduction of the PSI end electron acceptors, trapped energy flux per reaction center and PSII antenna size displayed strong positive correlation with biomass. Additional analysis revealed that 100 mM NaCl significantly reduced leaf linear electron flux under low-light conditions, regardless of whether seedlings had been pre-treated with 50 mM NaCl or not. Conclusions NaCl-induced salt tolerance was related to the robust photosynthetic machinery.

Assessing salt tolerance in plants under field conditions is a challenging task. The objective of this research was to assess the effectiveness of different methods (leaf disc assay and pot experiment) for evaluating salt tolerance in rice. Using two varieties with different salt tolerance, Changmaogu (CM) and 9311, under three NaCl levels (0, 0.3%, and 1.0%), we evaluated the photosynthetic performance in terms of chlorophyll content in leaf disc assays, as well as the photosynthetic rate (Pn), chlorophyll content, linear electron flow (LEF), and non-photochemical quenching (NPQ), in a semi-controlled pot experiment. In the leaf disc assay, CM showed a smaller decrease in chlorophyll content compared to 9311, especially under 1.0% salinity. Simultaneously, in the pot experiment, the CM variety employed flexible photosynthetic strategies, actively decreasing LEF and Pn after 5 days of salt stress (day 5) and then increasing photosynthetic capacity (chlorophyll content, LEF, and Pn) on day 10. Notably, the total chlorophyll content for the CM variety under 1.0% salinity was significantly higher than in the control, showing a 25.0% increase. Additionally, CM demonstrated NPQt sensitivity under 0.3% salinity, requiring an LEF of 150 to achieve an NPQt value of 3.0, compared to an LEF of 180 in the control. These results suggest that a simple leaf disc assay may not fully capture the adaptive mechanisms of rice plants under salinity stress. Therefore, we advocate for the use of more comprehensive methods, such as outdoor pot or field experiments, to gain a deeper understanding and more accurate evaluation of salt tolerance in rice.

Abstract Pulsed amplitude modulation (PAM) chlorophyll a fluorescence provides information about photosynthetic energy transduction. When reliably measured, chlorophyll a fluorescence provides detailed information about critical in vivo photosynthetic processes. Such information has recently provided novel and critical insights into how the yield potential of crops can be improved and it is being used to understand remotely sensed fluorescence, which is termed solar‐induced fluorescence and will be solely measured by a satellite scheduled to be launched this year. While PAM chlorophyll a fluorometers measure fluorescence intensity per se, herein we articulate the axiomatic criteria by which instrumentally detected intensities can be assumed to assess fluorescence yield, a phenomenon quite different than fluorescence intensity and one that provides critical insight about how solar energy is variably partitioned into the biosphere. An integrated mathematical, phenomenological, and practical discussion of many useful chlorophyll a fluorescence parameters is presented. We draw attention to, and provide examples of, potential uncertainties that can result from incorrect methodological practices and potentially problematic instrumental design features. Fundamentals of fluorescence measurements are discussed, including the major assumptions underlying the signals and the methodological caveats about taking measurements during both dark‐ and light‐adapted conditions. Key fluorescence parameters are discussed in the context of recent applications under environmental stress. Nuanced information that can be gleaned from intra‐comparisons of fluorescence‐derived parameters and intercomparisons of fluorescence‐derived parameters with those based on other techniques is elucidated.