The cultivation strategy of ‘postponed nitrogen with increased panicle fertilization (PNIPF)’ boosts rice yield but the balance between lodging remains unclear. We evaluated three panicle nitrogen ratios (0%, 20% and 40% of total 165 kg N ha−1) in two late indica rice varieties (Meixiangzhan 2 and Taiyou 871) to assess this trade-off. Results demonstrated that: (1) Compared to R0, PNIPF to 20% showed no difference on yield, while R4 raised grain yield by 4.84% and 8.69% but increased lodging index by 30.5% and 35.8% in TY871 and MXZ2. (2) Relative to R0, R4 induced taller plants with elevated center of gravity, reduced culm diameter, diminished culm mechanical strength, and decreased structural carbohydrate content (cellulose −29.2%, lignin −23.8%). The effect of R2 is weaker than R4 on plant morphology. (3) Compared to R0, R4 manifested more profound anatomical deterioration than R2. (4) Significant variety differences existed; PNIPF exhibited a more profound impact on MXZ2 than TY871 by inferior morphological, physiological and anatomical traits. We recommend limiting panicle nitrogen to below 20% to achieve synergistic improvement of yield and lodging resistance in high-quality late indica rice production.
Photosynthesis is the main determinant of crop yield. Drought is reported to be one of the major abiotic stresses that negatively affect photosynthetic capacity. This is the first report on the effect of drought-induced memory on the photosynthetic activity of potato. Two potato cultivars, Cayuga and Dalila, which were grown under non-stressed conditions, were studied. The plants were propagated from seed tubers that were produced by plants grown under non-restricted (non-primed tubers) and restricted (drought-primed tubers) water conditions. In Dalila plants, 14 JIP-test parameters were significantly altered in drought-primed plants, as compared to the control, of which PIinst, PIABS and DFABS showed the highest values. In Cayuga plants, the observed changes in JIP-test parameters were not significant. In contrast, there was no significant variation in the photosynthetic pigment content (chlorophyll a, chlorophyll b and carotenoids) in drought-primed Dalila plants, whereas drought-primed Cayuga plants had significantly higher values for leaf pigment content compared to the control. In Dalila and Cayuga plants, cell cycle progression was not affected by drought-induced memory. Gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment for differentially expressed genes (DEGs) in drought-primed Dalila plants showed that photosynthesis-related pathways may be essential in response to drought-induced memory. The top three categories included ‘photosynthesis, light harvesting in photosystem I’, ‘response to light stimulus’ and ‘photosynthesis-antenna proteins’. In contrast, only a few DEGs were observed in the progeny of Cayuga-primed vs. Cayuga-non-primed plants. Potato tubers are strong sink organs. Our results suggest that the maintenance or fading of drought-induced memory involves processes related to photosystem activity, which may result in the observed variation in potato tuber productivity under non-stressed conditions.
High temperatures impact sweet maize production; however, their specific effects on grain yield and kernel quality across different growing seasons remain unquantified. This study investigated high-temperature season effects, evaluated the yield and kernel quality responses in two sweet maize hybrids with different heat tolerance, and analysed the response mechanisms of dry matter accumulation (DMC), flowering, and grain filling in South China. Two contrasting sweet maize hybrids were planted annually in spring, summer, and autumn over a 2-year field experiment in Guangdong, South China. An evaluation of extreme degree days at different growth stages revealed that the sweet maize crops experienced high-temperature stress during their reproductive stages in the spring and summer growing seasons. In the high-temperature season, ‘HMT8’ showed heat sensitivity, with the grain yield significantly decreasing because of the lower kernel weight. The reduced grain-filling rates, especially in the early stages, contributed to lower kernel weight, which may be related to the decreased leaf area index (LAI) and post-anthesis DMC. Comparatively, ‘GLT27’ was heat-tolerant, with the grain yield slightly increasing because of the increased kernel number. However, it appeared cold-sensitive during the grain-filling stages in autumn. ‘GLT27’ exhibited stable or slightly increased pollen viability, LAI, post-anthesis DMC, and grain-filling rates. Furthermore, both hybrids showed reduced sucrose and elevated free amino acid content in the high-temperature seasons. Early grain-filling and post-anthesis DMC rather than reproductive organ viability may limit sweet maize during high-temperature seasons. Managing crops by selecting varieties and cultivation practices for different annual growing seasons is crucial.
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