In stressful environments, invasive plants acclimate more efficiently than native plants and hybridization mainly contributes to this process. We examined changes in the morphological characteristics, photosynthetic characteristics, and antioxidant capacity of Sphagneticola trilobata and its hybrids in a low-light environment to explore their invasiveness, with Sphagneticola calendulacea serving as the control. The morphological plasticity of S. trilobata was not dominant, the maximal photochemical efficiency of PSII, actual quantum yield of PSII, and electron transport rate of PSⅡ increased and nonphotochemical quenching decreased, while S. calendulacea and the hybrid produced opposite results. S. trilobata showed fewer spots stained for reactive oxygen species in tissues, with an increase in superoxide dismutase activity. Although S. trilobata is a heliophilous plant, we found that the shade tolerance of S. trilobata and the hybrid were stronger than that of S. calendulacea, which may be one important mechanism of invasion.
Shade treatment was applied to tall fescue with 30% full light. The results showed that shade increased chlorophyll (Chl) content per unit leaf mass, decreased the Chl a/b ratio in the mature leaves, and decreased effective quantum yield based on Chl fluorescence compared to the full light treatment. Shade stress did not cause increased contents of malondiadehyde at the early stages of leaf development. However, normalized vegetation indices were able to detect shade stress. Chloroplasts in the shaded leaves are arranged tightly against the periclinal cell wall and are in a spindle shape. There were no differences in the number of grana per chloroplast or grana size (thylakoids per granum) between shade and full light treatment. In conclusion, tall fescue leaves showed unique ultrastructure changes. Turfgrass managers could use vegetation indices developed from the leaf light reflection spectrum as an effective tool to assess shade stress levels and make management decisions.
Apple rootstock seedling M.9-T337 was selected to explore the effect of drought stress. The findings indicated that the relative water content of both the leaf and soil gradually decreased with an increase in drought stress. The water-use efficiency of the leaves increased gradually but decreased sharply after 20 d of drought. Changes in the gas-exchange parameters and chlorophyll fluorescence parameters reflected the gradual decrease in the photosynthetic capacity of the plants with drought stress duration. Infrared thermal imaging showed significant temperature differences between the drought-stressed and control plants after 15 d of drought treatment. When irreversible damage occurred under drought stress, the crop water-stress index and relative water content of the leaf and soil were 0.7, 60.5, and 17.8%, respectively. Based on the results, we formulated a drought stress-grade standard. Further, we established that the best time for irrigation is when drought stress reaches grade 3., D. T. Gao, C. Y. Shi, Q. L. Li, Z. F. Wei, L. Liu, J. R. Feng., and Obsahuje bibliografické odkazy
The effects of different light-emitting diode (LED) lights on saffron growth and photosynthetic characteristic were explored. Physiological mechanisms were explained by chlorophyll a fluorescence transient curves (OJIP) and JIP-test parameters. A decrease in the red to blue light ratio resulted in negative effects, particularly for monochromatic blue (B) LED light; saffron seedlings showed reduced chlorophyll accumulation, inhibited leaf elongation, and decreased photosynthetic performance. In the OJIP curve, the higher positive K-band observed for B LED light indicated that oxygen-evolving complex activation significantly decreased. B LED light inhibited the electron transport between primary quinone acceptor and secondary quinone acceptor as well as the existence of reducing plastoquinone centers, and increased energy dissipation of reaction centers. Otherwise, the red to blue light ratio of 2:1 had a positive effect on saffron cultivation, resulting in the longest leaf lengths, highest chlorophyll content, and photosynthetic characteristics. This study provides theoretical guidance for saffron agricultural practices.
Anticipating warming related to climate change, commercial mango plantations in China have been shifting from lower to higher elevations. Such a practice may expose mangoes to climatic conditions that could affect photosynthesis. Photosynthesis research on mango has previously examined mature plantations but exploring adequate functions before the time of fruit production is necessary for later crop success. Therefore, we established two main commercial mango cultivars, Tainong No. 1 and Jinhuang, at 450 m and 1,050 m and examined their photosynthetic performance. Our results showed that photosynthetic capacity parameters, including maximum photosynthetic rate, apparent quantum yield, maximum carboxylation rate, and photosynthetic electron transport rate, were significantly different between cultivars due to elevation and positively correlated with leaf nitrogen per area. Moreover, the seasonal gas exchange of the two cultivars showed variations due to elevation, particularly during the warmer seasons. Therefore, elevation affects the photosynthetic performance of these mango cultivars.
The frequent occurrence of monsoon winds usually leads to the formation of inverted soybean leaves. However, the effect of leaf inversion on photosynthetic capacity remains unclear. The responses of leaf anatomical traits, chlorophyll fluorescence induction kinetics parameters, photosynthetic capacity, and nonstructural carbohydrates of fully expanded leaves to inversion of leaves in two soybean cultivars were studied. Leaf inversion decreased the stomatal size and thickness of developed leaves. The net photosynthetic rate was significantly reduced under leaf inversion, which resulted from reduced excitation energy trapping and electron transport of PSII reaction center. Leaf inversion increased leaf temperature 10 d after leaf inversion but reduced the instantaneous water-use efficiency compared to normally oriented leaves. Due to the decreased light-saturated net photosynthetic rate, the soluble sugars of light-sensitive cultivar decreased significantly. In summary, leaf inversion deactivated the PSⅡ reaction centers, reduced photosynthesis and nonstructural carbohydrates in upper canopy soybean leaves.
Secondary soil salinization causes plant stress, which can be relieved by different ratios of red to far-red light (R:FR). Our study aimed to elucidate the role of low R:FR ratios treatments on photosynthesis and growth of tomato seedlings in salinized soils. Tomato seedlings were treated under three R:FR ratios and calcium nitrate was applied simultaneously. The results showed that the treatments under low R:FR ratios stimulated growth parameters of tomato seedlings under calcium nitrate stress, the best impact being achieved at the R:FR ratio of 0.7 in this experiment. Low R:FR ratios treatments increased proline content as well as PSII maximum efficiency, actual electron transport operating efficiency, and photochemical quenching of tomato seedlings under calcium nitrate stress but decreased the value of nonphotochemical quenching. Moreover, low R:FR ratios treatments promoted net photosynthetic rate and increased the expression of a Rubisco gene. In conclusion, low R:FR ratios treatments could improve the salt resistance of greenhouse tomato plants.
The formation of economic yield and fruit quality of Roxburgh rose (Rosa roxburghii Tratt.) depends essentially on its source-sink interaction. Thus, a pruning experiment was conducted to assess the effects of source-sink regulation on photosynthetic physiology and fruit yield of Roxburgh rose, which was of great significance to production. Cutting off vegetative branches reduced physiological fruit loss and malformed fruits but increased single fruit quality and yield. Results revealed that the stomatal characteristics, the composition of mesophyll tissue, and photosynthesis of leaves on reproductive branches were significantly affected by the ratio of the vegetative and reproductive shoots. Our data indicated that the source-sink ratio could reflect the balance between vegetative growth and reproductive growth of the tree during the whole fruit period. Fruit tree pruning had guiding significance for improving the fruit yield of Roxburgh rose.
Increasing the efficiency of photosynthesis in sugarcane canopies is the key for improving crop yield. Herein, we evaluated the photosynthetic performance along the canopy of ten sugarcane cultivars and three Saccharum species. Canopy morphological traits were evaluated, and leaf gas exchange was measured in the first (sun-exposed, +1) and the fourth (shaded, +4) fully expanded leaves and under low- and high-light conditions. Similar photosynthetic capacity was found in leaves +1 and +4 under high light in genotypes with a high leaf area index and a high fraction of the sky blocked by the foliage (> 85%). Interestingly, such canopy characteristics cause low light availability to leaves +4, suggesting the photosynthetic acclimation of these leaves to self-shading in some genotypes. We highlight IACCTC06-8126 and CTC4 as those genotypes with higher canopy photosynthetic capacity, presenting high leaf area, high photosynthetic rates in sun-exposed leaves, and high responsiveness of shaded leaves to increasing light availability.
Photosynthesis can be affected by nanoparticles (NPs) both negatively (e.g., through decreasing the chlorophyll content and electron transport rate, damages to chloroplast components, etc.) or positively (e.g., via enhancing chlorophyll content, the activity of Rubisco enzyme, the performance of PSII, and CO2 harvesting, as well as broadening the chloroplast photoabsorption spectrum). Enhanced photosynthetic efficiency could be a possible impact of NPs on photosynthetic organisms of major economic and ecological significance (e.g., crops and algae), which warrants an in-depth understanding of NPs interactions with chloroplast and its structural components (e.g., thylakoid membranes), signaling molecules, and pathways involved in photosynthesis. In this review, we comprehensively explore the potential effects of NPs on photosynthesis in different photosynthetic organisms (terrestrial plants, aquatic plants, and algae), and highlight research limitations and possible practical implications.