•Alkaline stress caused growth inhibition of cucumber seedlings.•Application of salicylic acid (SA) matained ion balance under alkaline stress.•Application of SA improved photosynthetic capacity ...under alkaline stress.•Application of SA alleviated oxidative damage caused by alkaline stress.•Application of SA improved alkaline-tolerance of cucumber seedlings.
Although various works have been done in alleviating effects of exogenous salicylic acid (SA) on abiotic stress in plants, it was not reported whether exogenous SA had effects on alkaline-tolerance of plants. In the present study, we found that the effect of exogenous SA depended on the concentration and 75 μM SA showed the best remission effect on cucumber plants under alkaline stress. The effect of 75 μM SA on detailed change of photosynthetic capacity, reactive oxygen metabolism and ionic homeostasis in alkaline-treated cucumber plants were further investigated. Alkaline stress significantly caused ion imbalance, decreased photosynthetic pigment content, inhibited PSII activity and net photosynthetic rate. With prolonging stress time, electrolyte leakage, MDA and H2O2 contents were significantly increased in cucumber leaves, while antioxidative enzymes activity and ascorbate-glutathione cycle increased first and then decreased. Application of 75 μM SA reduced Na+ accumulation, maintained ionic homeostasis and normal operation of photosystem, enhanced the reactive oxygen species (ROS) scavenging system, reduced oxidative damage, and alleviated lipid peroxidation, thereby improved the alkaline-tolerance of cucumber plants.
•Photosynthetic capacity of maize was predicted from airborne hyperspectral imagery.•Radiative transfer modeling surrogates and PLSR were used to predict leaf and canopy traits.•Soil and leaf angle ...information can reduce ill-posed radiative transfer model retrieval.•Canopy structure spectral signals enhance the accuracy of predicting canopy photosynthetic traits.•Synergistic use of process-based and data-driven approaches facilitates trait retrieval.
Nitrogen is an essential nutrient that directly affects plant photosynthesis, crop yield, and biomass production for bioenergy crops, but excessive application of nitrogen fertilizers can cause environmental degradation. To achieve sustainable nitrogen fertilizer management for precision agriculture, there is an urgent need for nondestructive and high spatial resolution monitoring of crop nitrogen and its allocation to photosynthetic proteins as that changes over time. Here, we used visible to shortwave infrared (400–2400 nm) airborne hyperspectral imaging with high spatial (0.5 m) and spectral (3–5 nm) resolutions to accurately estimate critical crop traits, i.e., nitrogen, chlorophyll, and photosynthetic capacity (CO2-saturated photosynthesis rate, Vmax,27), at leaf and canopy scales, and to assess nitrogen deficiency on crop yield. We conducted three airborne campaigns over a maize (Zea mays L.) field during the growing season of 2019. Physically based soil-canopy Radiative Transfer Modeling (RTM) and data-driven approaches i.e. Partial-Least Squares Regression (PLSR) were used to retrieve crop traits from hyperspectral reflectance, with ground truth of leaf nitrogen, chlorophyll, Vmax,27, Leaf Area Index (LAI), and harvested grain yield. To improve computational efficiency of RTMs, Random Forest (RF) was used to mimic RTM simulations to generate machine learning surrogate models RTM-RF. The results show that prior knowledge of soil background and leaf angle distribution can significantly reduce the ill-posed RTM retrieval. RTM-RF achieved a high accuracy to predict leaf chlorophyll content (R2 = 0.73) and LAI (R2 = 0.75). Meanwhile, PLSR exhibited better accuracy to predict leaf chlorophyll content (R2 = 0.79), nitrogen concentration (R2 = 0.83), nitrogen content (R2 = 0.77), and Vmax,27 (R2 = 0.69) but required measured traits for model training. We also found that canopy structure signals can enhance the use of spectral data to predict nitrogen related photosynthetic traits, as combining RTM-RF LAI and PLSR leaf traits well predicted canopy-level traits (leaf traits × LAI) including canopy chlorophyll (R2 = 0.80), nitrogen (R2 = 0.85) and Vmax,27 (R2 = 0.82). Compared to leaf traits, we further found that canopy-level photosynthetic traits, particularly canopy Vmax,27, have higher correlation with maize grain yield. This study highlights the potential for synergistic use of process-based and data-driven approaches of hyperspectral imaging to quantify crop traits that facilitate precision agricultural management to secure food and bioenergy production.
Mountains play an important role in the carbon cycle of the terrestrial ecosystem and are one of the most sensitive ecosystems to climate change. However, our current knowledge regarding the ...physiological responses of alpine plants to environmental changes remains limited due to the severe climatic conditions prevailing in these high-altitude regions. Therefore, this study quantified the variations in photosynthetic rates (An) and identified their driving factors of herbaceous plants, shrubs, and trees along an elevation gradient (2200 m asl to 3200 m asl) on Mount Gongga. Elevation emerged as a significant determinant of An, with a general increase observed, albeit followed by a decline above 3000 m asl. In high-altitude regions, trees displayed more significant fluctuations in An compared to herbaceous plants and shrubs. The lower levels of atmospheric carbon dioxide concentration (eCO2) and temperature (T) in high-altitude regions resulted in a 16 % increase in An for herbaceous plants, 60 % increase for shrubs, and 43 % increase for trees compared to the low-altitude areas. Structural equation modeling (SEM) analyses underscored the considerable impact of environmental factors on An. Notably, PAR, eCO2, and gs were identified as positive influencers, while other factors exerted negative effects. Our results further highlighted that trees were subject to greater constraints from multiple factors compared to herbs and shrubs, aligning with the outcomes of our variance analysis. In summary, our study presents a comprehensive assessment of vegetation responses to environmental factors along elevational gradients. The significance of An in plants at high altitude to external factors suggests the potential adaptability of alpine plants, and also indicates that changes in photosynthetic physiological functions at high altitude should be paid more attention to in the study of climate change.
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•Quantify and analyze alpine plant responses to Mount Gongga's environmental changes.•This study reveals mechanisms causing photosynthesis fluctuations in high-altitude trees.•Studies high-altitude plants' increased photosynthesis rates.•Explored climate, soil, and leaf area impacts on highland vegetation.
•Pure blue light induced shade avoid response is species dependent.•Effects of pure red light on leaf photosynthetic function in cucumber is stronger than in tomato.•Cucumber is more sensitive to ...alterations in red/blue light ratio than tomato.
Red and blue light play pivotal roles on mediating plant developmental processes, while evidence is accumulating that responses to changes in light spectrum are species dependent. This study aims to evaluate responses in cucumber and tomato which are major horticultural species and model plants for light spectrum studies, to red and blue light at different integrational levels, and at distinguishing to what extent these two species differ from each other. Plants were grown under a range of blue (B) light percentage: 0B, 25B, 50B, 75B, and 100B, the remaining percentage was red (R) light, with identical photosynthetic photon flux density (100 μmol⋅m−2⋅s-1). Peak intensities of B and R were at wavelengths of 454 nm and 663 nm, respectively. We showed that an increase in the blue light percentage resulted in a decreased plant height in both species, except under 100B where cucumber exhibited the greatest plant height, while in tomato the tallest plants were under 0B. Cucumber grown under 100B had the greatest shoot dry weight and largest leaf area, whereas in tomato 25B had the greatest plant growth. In both species, the function of leaf photosynthetic apparatus was strongly repressed by 0B, compared with the other treatments, while the magnitude of this repression was greater in cucumber than in tomato. Leaf total nitrogen, total carbon and chlorophyll contents were lowest under 0B in both species. HY5 expression exhibited limited response to 0B, but it was significantly increased by blue light (i.e. 50B and 100B) except with cucumber that was non-sensitive to 100B. We conclude that blue light is needed for maintaining normal plant growth and developmental processes, and cucumber is more sensitive to red and blue light than tomato, indicating that plant responses to red and blue light are species specific. Our research stresses the significance to consider the species or even cultivar difference when drawing conclusions from light quality study.
•Reduction of CHL concentration in leaves did not affect the number of papaya fruits per plant.•Dark-green papaya leaves had reduced number of fruits under water stress.•The ψsoil of around −38 kPa ...can be considered as a threshold for papaya irrigation at studied soil type.•-Pale-green papaya genotypes had an increased agronomic water use efficiency.•-Pale-green papaya genotypes can have potential use as an alternative to mitigate the effects of water stress.
In the context of increasing drought frequencies, water sensitive plant species need to have defined irrigation thresholds. One such species is papaya (Carica papaya L.), with a current demand for the selection of drought tolerance genotypes. The aim of this study was to evaluate the growth, leaf gas exchanges, sap flow and chlorophyll (Chl) fluorescence in two papaya genotypes (pale-green leaf ‘Golden’ - G and dark-green leaf ‘Aliança’ – AL) under soil water deficit (Ψsoil) conditions. The experiments were carried out in the field, in an unconsolidated alluvial sediment soil type. The two papaya genotypes, contrasting in their leaf Chl contents, were grown under irrigated (I, Ψsoil of -12 kPa), and non-irrigated (NI, Ψsoil gradually diminished from - 23 to -311 kPa) conditions for 41 days. Leaf gas exchanges, xylem sap-flow, green intensity (SPAD index), plant height, trunk diameter and leaf area were measured five times, following Ψsoil decreases. At the lowest Ψsoil (-311 kPa), the Chl photochemistry and fruit number measurements were performed. Intrinsic water use efficiency was higher in the GNI than in the ALNI genotype. Leaf temperature and photochemical efficiency was not affected by soil water restrictions in GNI and ALNI. The water deficit effect on growth traits was linked to whole canopy assimilation, due to the higher leaf area in ALI than GI, or in ALNI than in GNI, once the leaf assimilation rate was similar between those treatments. The ψsoil of ca. -30 kPa can be considered as a threshold for papaya irrigation for the soil type studied here. Soil water stress did not affect the number of fruits in GNI, whilst this was reduced by 83% in ALNI compared to irrigated plants, indicating that pale-green leaf papaya genotypes are an alternative to cope with water stress.
The purpose of this research was to explore the integrative effects of tillage rotary tillage (RT), subsoiling tillage (SST), and no-tillage (NT) and nitrogen (N) fertilizer rate (N2, 200 kg N ha−1; ...N3, 300 kg N ha−1) on net photosynthetic rate (Pn), hormonal changes in grains, grain filling parameters, grain yield components, and grain yield of maize (Zea mays L.). The relationship among the yield components and grain filling parameter was also investigated. The results indicated that, on the average, tillage had no significant effect on maize yield under either N2 or N3, N rate had no significant effect on maize yield under RT and NT, only under SST, N3 increased maize grain yield significantly over N2 by 10.79%. Further on, SST with N3 enhanced Pn and promoted dry matter accumulation. The content of indole-3-acetic acid (IAA) and cytokinin (CTK) maintained a higher level over time under the SST with N3 compared with other treatments, gibberellic acid (GA) under SST with N3 had the lowest content from 21 to 28 DAP in two years. The grain filling parameter showed that SST with N3 promoted average grain filling rate and increased the weight of gradual increase period, rapid increase period, and slight increase period. It is concluded that the no-tillage with 200 kg N ha−1 is the suitable tillage as it saves tillage input, but subsoiling tillage had the advantage under 300 kg N ha−1, which improved photosynthetic rate, promoted dry matter accumulation and transport, optimized the balance of hormones, subsequently ameliorated the grain filling process, thus promoting kernels weight and ultimately increased yield.
•Maize yield response to tillage and nitrogen rate was mainly due to kernels weight difference in the Loess Plateau.•Subsoiling tillage with 300 kg N ha−1 optimized hormones and grain filling, resulting in increased kernels weight.•Under 200 kg N ha−1, no-tillage is the suitable practice as it saves tillage input without yield penalty.
Photosynthetic responses to altitude Wang, Han; Prentice, I. Colin; Davis, Tyler W. ...
The New phytologist,
02/2017, Letnik:
213, Številka:
3
Journal Article
Light-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and more flexible and feasible spectral control compared with other ...artificial lighting. The combined effects of red and blue (RB) LED with or without green (G) LED light and white LED light on lettuce (
Lactuca sativa
L.) growth and physiology, including nitrate content, chlorophyll fluorescence, and phytochemical concentration before harvest, were investigated. Continuous light exposure at preharvest can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants. Nitrate accumulation is dependent on the spectral composition and duration of treatment: lettuce exposed to continuous RB (with or without G) LED light with a photosynthetic photon flux (
PPF
) of 200 µmol·m
−2
·s
−1
exhibited a remarkable decrease in nitrate content at 24 hour compared with white LED light treatment at the same
PPF
. In addition, RB LED light (R:B = 4:1) was more effective than white LED light at the same
PPF
in facilitating lettuce growth. Moreover, continuous LED light for 24 hours significantly enhanced free-radical scavenging activity and increased phenolic compound concentrations. We suggest that 24 hours continuous RB LED with G light exposure can be used to decrease nitrate content and enhance lettuce quality.
Significant variation in photosynthesis and growth in 64 wheat cultivars was explained by differences in photosynthetic capacity, operation and CO2 diffusion. Natural variation in photosynthesis is ...an underutilized resource for potential crop improvement.
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