Journal of Agronomy and Crop Science最新文献

Photochemical reflectance index (PRI) has been a promising indicator for estimating vegetation photosynthetic efficiency. However, its capability to track drought stress-induced changes in canopy radiation use efficiency (RUE) and the underlying mechanisms remains insufficiently explored, largely due to the confounding effects of soil background and canopy characteristics. This study aimed to explain how the canopy PRI responds to drought stress and quantify the relative contributions of soil moisture and canopy characteristics to its variability. Using maize field experimental data across varying drought treatments, we found that drought significantly altered the PRI-RUE relationship, with canopy PRI exhibiting a stronger correlation with RUE under increasing soil drying. This enhancement in the PRI-RUE relationship was primarily attributed to changes in canopy structure and physiological characteristics. Specifically, the fraction of absorbed photosynthetic available radiation (fAPAR), canopy water content (CWC) and canopy chlorophyll content (CCC) were more related to PRI than leaf area index (LAI). While available soil water content (ASWC) was not directly linked to PRI, a positive linear relationship emerged after accounting for the effects of canopy characteristics, particularly fAPAR. Furthermore, fAPAR and LAI were identified as the most important direct and indirect factors influencing canopy PRI, respectively. These findings underscore the importance of considering fAPAR's contribution to accurately estimate photosynthetic efficiency and monitor crop stress under soil drying scenarios. By demonstrating how drought strengthens the PRI-RUE relationship and elucidating its underlying mechanisms, this study provides insights for improving crop stress monitoring and photosynthetic capacity assessment.

High temperature disrupts physiological processes in rice, including impairing the function of photosystem II and leading to reduced productivity. However, understanding of the short-term effects of elevated temperatures on photosystem II function and its protein composition in rice seedlings remains limited. This study examined the effect of short-term exposure to elevated temperature (25°C–40°C) on photosystem II function, photosynthetic pigments, psbA gene expression and D1 protein in three rice seedlings, namely Dular, IR64 and KDML105. The findings revealed that a short-term temperature of 30°C–35°C activated photosystem II function, as reflected by improved photosystem II efficiency and increased levels of photosynthetic pigments. In contrast, a temperature of 40°C impaired and suppressed photosystem II function. A short-term temperature of 40°C activated the psbA gene expression and D1 protein synthesis in Dular, while inhibiting these processes in IR64 and KDML105. This suggested that short-term temperatures between 30°C and 35°C were ideal for photosystem II function at the metabolic level, whereas 40°C adversely affected photosystem II function. At the molecular level, Dular demonstrated rapidly repaired psbA gene expression and D1 protein synthesis, with high activity observed after short-term exposure to 40°C. Meanwhile, IR64 and KDML105 experienced significant molecular damage under the same conditions. These findings proved Dular as heat-tolerant, whereas IR64 and KDML105 were classified as heat-sensitive and moderately heat-sensitive, respectively.

The occurrence of wheat pre-harvest sprouting (PHS) has been intensified with global climatic change and increasing rainfall from 1981 to 2020, which has led to a drastic reduction in wheat quality and yield. Therefore, scientific assessments of the potential climatic risk of wheat PHS in different areas based on historical meteorological data help identify the high-risk areas, select suitable wheat cultivars and optimise cultivation measures for wheat production. However, to date, risk assessment criteria have not been established for evaluating the potential climatic risks associated with wheat PHS in different areas. This study analysed temperature and relative humidity change trends and identified the boundary line between the Yellow and Huai River Valley Facultative Wheat Zone and the Middle and Lower Yangtze River Valley Winter Wheat Zone using climatically similar points. The experimental material comprised the wheat PHS-sensitive variety Xiaoyan 22. Wheat PHS risk assessment criteria were proposed based on the whole ear germination test and daily temperature and relative humidity data collected during the wheat harvest period from 1981 to 2020 in the two wheat regions. The climatic risk associated with wheat PHS was graded for these two areas. Our results showed that from 1981 to 2020, the temperature increased by 0.38°C/10 years and 0.26°C/10 years, while the relative humidity decreased by 1.8%/10 years and 0.39%/10 years during the wheat harvest period in the two wheat regions. Further analysis of the factors influencing the climate boundary between the Yellow and Huai River Valley Facultative Wheat Zone and the Middle and Lower Yangtze River Valley Winter Wheat Zone revealed that, from 1986 to 2020, the eastern section of the climate boundary exhibited significant southward or northward migration trends in Anhui and Jiangsu Provinces. The central section of the similar climate boundary in Henan and Hubei Provinces also showed a southward trend but a relatively small range, whereas the western section fluctuated up and down the original dividing line, with a northward migration trend in Gansu Province. A new risk assessment indicator, P, was proposed in this study based on meteorological data from 1981 to 2020 in China. During this period, the wheat PHS risk increased from north to south and west to east in the Yellow and Huai River Valley Facultative Wheat Zone and from north to south in the Middle and Lower Yangtze River Valley Winter Wheat Zone. Furthermore, the overall wheat PHS climate risk in the Yellow and Huai River Valley Facultative Wheat Zone was lower than that in the Middle and Lower Yangtze River Valley Winter Wheat Zone. Risk assessments of wheat PHS distribution and damage will provide a scientific basis for the accurate distribution of pre-harvest sprouting-resistant wheat varieties and improve the resistance to natural disasters and the safety of wheat production.

To understand the impact of salinity heterogeneity on maize growth, a split-root experiment involving both homogeneous and heterogeneous salinity environments was designed. Four homogeneous salinity levels (2, 4, 6 and 8 g L⁻¹), four heterogeneous treatments (0/2, 0/4, 0/6, and 0/8 g L⁻¹) and a control (CK) with 0 g L⁻¹ NaCl were applied to respective sides of split-root pots. Findings revealed that while heterogeneous salinity treatments up to 8 g L⁻¹ did not significantly alter seedling morphology, homogeneous salinity levels above 2 g L⁻¹ markedly inhibited growth. Both salinity stress scenarios enhanced physiological responses in maize leaves, peaking at 6 and 8 g L⁻¹ salinities. Stress-related indexes, including proline, malondialdehyde (MDA) and soluble sugar contents, increased by 105%, 189% and 95%, respectively, under heterogeneous salinity, versus 229%, 370% and 231% under homogeneous conditions, relative to the CK. Interestingly, the partial salinity stress of heterogeneous treatments stimulated root growth on the salt-free side, leading to an 11.7% average increase in root length compared to the control, thereby enhancing water uptake and biomass more effectively than homogeneous treatments. Principal component analysis (PCA) further indicated that heterogeneous salt stress could concurrently bolster morphological and physiological indicators in crops. These results highlight the critical role of salt-free zones in facilitating maize seedling growth and mitigating the adverse effects of salt stress under spatially variable salinity conditions.

Water deficiency has a serious effect on cotton productivity. Development of cotton bolls determines cotton fibre yield and quality and is affected by many environmental variables, including water availability. However, we know little about the effect of water stress on boll development and the final fibre yield and quality of the varieties with different boll sizes. In this study, cotton varieties with different boll sizes were used to compare the effect of water availability on boll development, characteristics of fibre yield and quality, seed components and seed vigour. The results showed that under the well-watered (WW) and water-deficit (WD) irrigation conditions, large boll (LB) and small boll (SB) varieties had a similar overall trend of boll volume change and accumulation of boll dry matter during boll development, but differed in the rate of dry matter accumulation and boll volume growth. Under WW treatment, the dry matter accumulation per boll of LB was significantly higher than that of SB at 42 days postanthesis (DPA), with a difference of 29.17%. WD led to a reduction in dry matter accumulation of bolls, and the dry matter accumulation in seed cotton and boll shell for LB varieties decreased by 20.45% and 3.24%, respectively, at 42 DPA. The corresponding decrease in SB varieties was, respectively, 16.76% and 2.81%, but the harvestable boll numbers per plant of SB varieties were 36.28% higher than that of LB varieties under WD irrigation. The lint yield of the SB varieties was 1042.45 kg·ha⁻¹ and the seed cotton yield was 2459.67 kg·ha⁻¹, which were also comparable to those of the LB varieties. WD treatment also reduced fibre length and strength, with a more significant impact on LB varieties. In addition, WD significantly increased the relative protein content of cottonseed but decreased the relative oil content, leading to a decrease in seed vitality. Under WD irrigation, compared to seeds of LB varieties, the seeds of SB varieties have higher germination potential. Compared with LB varieties, SB varieties required less dry matter accumulation for boll maturation and produced more harvestable boll numbers, resulting in a smaller impact on yield and quality under WD irrigation. In general, SB varieties are more tolerant to WD stress and are expected to have a better performance in severe arid areas.

Triple-helix transcription factors (GT factors) play a pivotal role in plant abiotic stress responses and growth and development. Named for their specific binding affinity to GT factors, they are clustered into five subgroups: GT-1, GT-2, GT-γ, SIP1 and SH4. In Phaseolus vulgaris, 43 GT family members have been identified through reference genome analysis. PvGT members exhibit uneven genomic distribution, and members within the same subgroup share similar gene structures and motifs. Cis-acting element analysis indicates the involvement of PvGTs in hormonal signalling and abiotic stress regulation. Collinearity analysis revealed four pairs of homologous PvGTs. To investigate their expression patterns, nine PvGTs with high expression levels were selected for quantitative real-time PCR (qRT-PCR) analysis. Among these, PvGT02, PvGT28, PvGT30 and PvGT34 were significantly upregulated under salt and drought stress. Functional characterisation demonstrated that PvGT02 significantly enhanced yeast tolerance to salt and drought stresses. These findings collectively contribute to our understanding of the PvGT family evolution in common bean, providing a foundation for further exploration. Additionally, PvGT02 emerges as a potential candidate gene for breeding salt and drought tolerance.

Because of inadequate freshwater resources and poor irrigation facilities, salinity and drought often co-occur for rice production in saline lands. The root is the primary and most vulnerable organ for detecting and perceiving salinity and drought stresses in soil. Still, little information is available on the root morpho-physiological characteristics and grain yield of rice when subjected to the combined salinity-drought stress. The present study was conducted under two salinity levels (NS, non-salinity treatment; S, salinity treatment) and three drought levels imposed from jointing to heading (ND, non-drought treatment; MD, moderate drought treatment; SD, severe drought treatment). Salinity and drought treatments shortened the duration from heading to maturity by 5–9 days and total growth duration by 3–6 days. Grain yield was reduced (p < 0.01 or p < 0.05) under salinity and drought, and the reduction was more significant under their combined stress. The aggravated yield loss under the combined salinity-drought was attributed to lower yield components relative to salinity and drought alone. The combined stress caused greater decreases in root and shoot biomass and root/shoot ratio at heading and maturity, although there was an increase in harvest index. Individual salinity and drought, and especially their combined stress, reduced root length and root volume at heading and maturity and increased reduction rates of root length and root volume after heading. Root-bleeding rate and root oxidative activity after heading were decreased under salinity and drought, and the decreases were greater under the combined salinity-drought stress; similar trends were detected for flag leaf photosynthetic rate and zeatin (Z) and zeatin riboside (ZR) contents in the root-bleeding sap and flag leaf. Our results suggested a greater yield penalty of rice when subjected to the combined stress of salinity and drought. Individual salinity, drought, and especially their combined stresses deteriorated root morphology and physiology, which shortened growth duration, accelerated plant senescence, weakened leaf photosynthesis and biomass accumulation, and led to poor grain yield.

Lodging is a major factor limiting soybean yield in maize–soybean intercropping system (IS). Potassium fertilisation significantly enhances the lodging resistance index by promoting dry matter accumulation in soybean. However, the physiological mechanisms through which potassium affects the lodging resistance index remain unclear, particularly under different planting systems. In this study, we analysed the relationships between photosynthetic characteristics, root system, stem physiology, stem morphological characteristics, dry matter and lodging resistance index of soybean based on field experiments. The soybean cultivar Jinong 40 was used in both maize–soybean intercropping (maize: soybean as 6:6) and monoculture soybean systems (MS) in a two-year field experiment (2022–2023), with five potassium fertilisation levels (0 kg ha⁻¹, 30 kg ha⁻¹, 60 kg ha⁻¹, 90 kg ha⁻¹ and 120 kg ha⁻¹). Potassium application significantly improved chlorophyll fluorescence parameters, dry matter accumulation, stem lignin synthesis enzyme activity (phenylalanine ammonia-lyase, tyrosine ammonia-lyase and cinnamyl alcohol dehydrogenase), lodging resistance index and grain yield, regardless of the planting system. However, no significant differences in lodging resistance index or grain yield were observed between the potassium rates of 90 kg ha⁻¹ and 120 kg ha⁻¹. Compared to 0 kg ha⁻¹, increased potassium rates increased stem diameter by 17.8% and 15.5%, while the ratio of stem length to stem diameter ratio (L/D) decreased by 27.2% and 26.8% in maize–soybean intercropping and monoculture soybean systems, respectively. Across the high potassium inputs (90 kg ha⁻¹ and 120 kg ha⁻¹), phenylalanine ammonia-lyase (2.6%) and cinnamyl alcohol dehydrogenase (3.9%) were higher in the maize–soybean intercropping system compared to the monoculture soybean system. For the two planting patterns, the lodging resistance index was found to be more dependent on stem enzyme activity (93.5% for IS and 75.3% for MS) and L/D ratio (−81.0% for IS and −83.8% for MS), rather than stem length or root characteristics. We conclude that potassium application optimises stem diameter, enhances stem lignin synthesis and reduces the L/D ratio, therefore improving the soybean lodging resistance index and yield, especially in the maize–soybean intercropping system.