Photosynthesis in non‐foliar organs plays an important role in crop growth and productivity, and it has received considerable research attention in recent years. However, compared with the capability of photosynthetic CO 2 fixation in leaves, the distinct attributes of photosynthesis in the non‐foliar organs of wheat (a C 3 species) are unclear. This review presents a comprehensive examination of the photosynthetic characteristics of non‐foliar organs in wheat. Compared with leaves, non‐foliar organs had a higher capacity to refix respired CO 2 , higher tolerance to environmental stresses and slower terminal senescence after anthesis. Additionally, whether C 4 photosynthetic metabolism exists in the non‐foliar organs of wheat is discussed, as is the advantage of photosynthesis in non‐foliar organs during times of abiotic stress. Introducing the photosynthesis‐related genes of C 4 plants into wheat, which are specifically expressed in non‐foliar organs, can be a promising approach for improving wheat productivity.
Photosynthesis in non-foliar organs plays an important role in crop growth and productivity, and it has received considerable research attention in recent years. However, compared with the capability of photosynthetic CO2 fixation in leaves, the distinct attributes of photosynthesis in the non-foliar organs of wheat (a C-3 species) are unclear. This review presents a comprehensive examination of the photosynthetic characteristics of non-foliar organs in wheat. Compared with leaves, non-foliar organs had a higher capacity to refix respired CO2, higher tolerance to environmental stresses and slower terminal senescence after anthesis. Additionally, whether C-4 photosynthetic metabolism exists in the non-foliar organs of wheat is discussed, as is the advantage of photosynthesis in non-foliar organs during times of abiotic stress. Introducing the photosynthesis-related genes of C-4 plants into wheat, which are specifically expressed in non-foliar organs, can be a promising approach for improving wheat productivity.
Elevated CO and use of endophytic microorganisms have been considered as efficient and novel ways to improve phytoextraction efficiency. However, the interactive effects of elevated CO and endophytes on hyperaccumulator is poorly understood. In this study, a hydroponics experiment was conducted to investigate the combined effect of elevated CO (eCO ) and inoculation with endophyte SaMR12 (ES) on the photosynthetic characteristics and cadmium (Cd) accumulation in hyperaccumulator . The results showed that eCO × ES interaction promoted the growth of . , shoot and root biomass net increment were increased by 264.7 and 392.3%, respectively, as compared with plants grown in ambient CO (aCO ). The interaction of eCO and ES significantly ( < 0.05) increased chlorophyll content (53.2%), Pn (111.6%), Pn (59.8%), AQY (65.1%), and Lsp (28.8%), but reduced Gs, Tr, Rd, and Lcp. Increased photosynthetic efficiency was associated with higher activities of rubisco, Ca -ATPase, and Mg -ATPase, and linked with over-expression of two photosystem related genes (SaPsbS and SaLhcb2). PS II activities were significantly ( < 0.05) enhanced with Fv/Fm and Φ(II) increased by 12.3 and 13.0%, respectively, compared with plants grown in aCO . In addition, the net uptake of Cd in the shoot and root tissue of . grown in eCO × ES treatment was increased by 260.7 and 434.9%, respectively, due to increased expression of SaHMA2 and SaCAX2 Cd transporter genes. Our results suggest that eCO × ES can promote the growth of . due to increased photosynthetic efficiency, and improve Cd accumulation and showed considerable potential of improving the phytoextraction ability of Cd by . .
Anoectochilus roxburghii was grown under different shade treatments-50%, 30%, 20%, and 5% of natural irradiance-to evaluate its photosynthetic characteristics, chloroplast ultrastructure, and physiology. The highest net photosynthetic rates and stomatal conductance were observed under 30% irradiance, followed in descending order by 20%, 5%, and 50% treatments. As irradiance decreased from 50% to 30%, electron transport rate and photochemical quenching increased, while non-photochemical quenching indexes declined. Reductions in irradiance significantly increased Chl a and Chl b contents and decreased Chl a/b ratios. Chloroplast ultrastructure generally displayed the best development in leaves subjected to 30% irradiance. Under 50% irradiance, leaf protein content remained relatively stable during the first 20 days of treatment, and then increased rapidly. The highest peroxidase and superoxide dismutase levels, and the lowest catalase activities, were observed in plants subjected to the 50% irradiance treatment. Soluble sugar and malondialdehyde contents were positively correlated with irradiance levels. Modulation of chloroplast development, accomplished by increasing the number of thylakoids and grana containing photosynthetic pigments, is an important shade tolerance mechanism in A. roxburghii.
Three summer maize (Zea mays L.) hybrids with different plant heights, DengHai661 (low-plant height hybrid, DH661), ChaoShi3 (medium-plant height hybrid, CS3), and XianYu335 (high-plant height hybrid, XY335), were used to explore photosynthetic characteristics of maize and its responses to plant density. Results showed that grain yield increased with the increase of plant density. At 90,000 plants ha(-1), grain yield of DH661 was the highest. With increasing plant density, yield increment of DH661 was biggest, while leaf area index (LAI), chlorophyll content, and net photosynthetic rate (P-n) of DH661 changed less with increasing plant density. Grain yield of DH661 at 90,000 plants ha(-1) increased by 34 and 21%, respectively, compared to that at 45,000 and 67,500 plants ha(-1), CS3 increased by 18 and 9%, respectively, and XY335 increased by 7% and not significant (ns), respectively. Before the flowering stage, the photosynthesis of leaves that just entered function stage played a dominant role. Aft er the flowering stage, the photosynthesis of top and middle leaves mainly played the leading role. The difference of P-n among three parts (top, middle, and bottom) of DH661 was less than that of XY335, and the same as the effect of plant density. There were no significant differences between DH661 and XY335 in the P-n of top leaves, while P-n of middle and bottom leaves of DH661 were significantly higher than that of CS3 and XY335. Visibly, low-plant height hybrid might be more beneficial for high yield cultivation under dense planting conditions.
The physiological and ecological responses of to different concentrations of nano-anatase TiO solutions were investigated in this study and we found that with foliar application of 0.1% (T1), 0.2% (T2) and 0.4% (T3) nano-anatase TiO solution the net photosynthetic rate of seedlings were lower, comparing with the control (CK) (no spraying). TiO solution had no effect on the carbon isotope values (δ C), indicating the lower photosynthetic capacity was not caused by stomatal limitation. The nitrogen isotope values (δ N) decreased, but the foliar metal elements, such as Mg, K and Mn contents were not affected by nano-anatase TiO which promoted the Cu uptake. Fourier transform infrared spectroscopy showed that the nano-anatase TiO enhanced the absorbance of leaves, especially for 1064, 1638, 2926 and 3386 cm bands, indicating the synthesis of carbohydrate and lipid compounds was a kind of mechanism under the toxic effects of nanonanoparticles. ► The responses of a woody plant to nano-TiO are studied. ► Non-stomatal limitation is the reason of lower photosynthesis. ► Light plays an important role in determining the interactions. ► The nano-TiO has not affect on C fractionation, but decreases δ N value. Photosynthetic active radiation plays an important role in determining the toxic effects of nano-TiO on seedlings, and the lowered photosynthesis is regulated by non-stomatal factors.
To explore the feasibility of reducing cadmium (Cd) concentrations and alleviating Cd toxicity via selenium (Se), this study investigated the effects of Se on the root morphology, photosynthetic parameters, and Se, and Cd concentrations in winter wheat under different Cd stress levels. Three Cd levels (0, 5 and 10 μM) and three Se levels (0, 1 and 5 μM) were applied in a hydroponics test. The results showed that increases in Cd stress significantly decreased the shoot and root dry matter weight, root length, root volume, root effective surface area, root total surface area, Se concentration, Se accumulation, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and intercellular CO concentration (Ci). Increases in Cd stress significantly increased the Cd concentration and accumulation in shoots and roots, the root average diameter, and the stomatal limiting value (Ls). There were significant relationships between the root Cd concentrations and the root morphology parameters, shoot Cd concentrations and photosynthetic characteristics of winter wheat. The Se and Se treatments effectively increased the shoot dry matter weight, root length, root volume, root effective surface area and root total surface area and decreased the shoot Cd concentration, when Cd stress was at the medium level (Cd ). Only the Se treatment effectively increased the Gs, Tr and Ci under the Cd treatment. When Cd stress was at the high level (Cd ), the Se treatment had greater effects on root growth than the Se treatment, the Se levels had no pronounced effect on the shoot dry weight and Cd concentration in winter wheat. Meanwhile, the root Se concentration was closely related to each root morphology parameter. Cd stress inhibited the root growth and leaf photosynthesis of winter wheat, and a high enough Se supply reduced the Cd toxicity by enhancing the root growth of winter wheat.
We studied the growth and photosynthetic characteristics of a toxic ( CS 506) and a nontoxic strain ( CS 509) of the bloom‐forming cyanobacterium C ylindrospermopsis raciborskii grown under identical experimental conditions. When exposed to light‐saturating growth conditions (100 μmol photons · m −2 · s −1 ), values for maximal photosynthetic capacity (P max ) and maximum quantum yield (F v /F m ) indicated that both strains had an equal ability to process captured photons and deliver them to PS II reaction centers. However, CS 506 grew faster than CS 509. This was consistent with its higher light requirement for saturation of photosynthesis (I k ). Greater shade tolerance of CS 509 was indicated by its higher ability to harvest light (α), lower photosynthetic light compensation point (I c ), and higher chlorophyll a to biovolume ratio. Strain‐specific differences were found in relation to non‐photochemical quenching, effective absorption cross‐sectional area of PS IIα‐centers (σ PS IIα), and the antenna connectivity parameter of PS IIα (J con PS IIα). These findings highlighted differences in the transfer of excitation from phycobilisome/ PS II to PS I, on the dependence on different pigments for light harvesting and on the functioning of the PS II reaction centers between the two strains. The results of this study showed that both performance and composition of the photosynthetic apparatus are different between these strains, though with only two strains examined we cannot attribute the performance of strain 506 to its ability to produce cylindrospermopsins. The emphasis on a strain‐specific light adaptation/acclimation is crucial to our understanding of how different light conditions (both quantity and quality) can trigger the occurrence of different C . raciborskii strains and control their competition and/or dominance in natural ecosystems.
The effects of 0.1 mu M 24-epibrassinolide (EBL) on plant growth (plant height, leaf area, fresh weight, and dry weight), chlorophyll content, photosynthetic characteristics, antioxidant enzymes, and chloroplast ultrastructure were investigated using cucumber seedlings (Cucumis sativus L. cv. Jinyou No. 4) with 80 mM Ca(NO3)(2) to induce stress. The presence of Ca(NO3)(2) caused significant reductions in net photosynthetic rate (P (N)), stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr) of leaves. In addition, Ca(NO3)(2) markedly reduced the chlorophyll content and inhibited photochemical activity, including the actual photochemical efficiency (I broken vertical bar PSII). In contrast, EBL increased the chlorophyll content, especially chlorophyll b, and minimized the harmful effects on photosynthesis caused by the Ca(NO3)(2). The application of EBL to the plants subjected to Ca(NO3)(2)-enhanced photochemical activity. EBL protected the photosynthetic membrane system from oxidative damage due to up-regulating the capacity of the antioxidant systems. Microscopic analyses revealed that Ca(NO3)(2) affected the structure of the photosynthetic apparatus and membrane system and induced damage of granal thylakoid layers, while EBL recovered the typical shape of chloroplasts and promoted the formation of grana. Taken together, EBL compensated for damage/losses by Ca(NO3)(2) due to the regulation of photosynthetic characteristics and the antioxidant system.
Determining the effects of a water deficit during periods of vegetative growth on photosynthetic traits and grain yield will provide a reasonable strategy for water-saving management of winter wheat ( L.) and exploited photosynthetic traits for the selection of drought tolerant winter wheat genotypes. A mobile rain shelter experiment was conducted using winter wheat cultivar to assess the effects of different levels of water stress on photosynthetic characteristics, dry matter translocation and water use efficiency (WUE) in the Shijiazhuang 8 (drought resistant) and Yanmai 20 (drought sensitive) cultivars at different growth stages. Three winter wheat growing stages were selected for assessment at follows: recovering-jointing, jointing-flowering and grain-filling, and the effects of four levels of soil water which were selected based on field capacity, on plants from seeding to mature stage were examined by controlling the irrigation as follows: 40–45% (severe stress), 55–60% (moderate stress), 65–70% (mild stress) and 75–80% (full irrigation) The results indicated that mild stress during the recovering-jointing stage improved the canopy structure prior to anthesis and maintained high canopy photosynthesis after anthesis, thus increasing winter wheat yields. Mild stress during all of the growth stages improved the distribution of assimilate to the grain prior to anthesis and increased the yield. Although moderate stress during all growth stages could improve dry matter translocation, the resulting yield was not high, as the accumulation of dry matter decreased after anthesis. Therefore, mild soil water stress can improve grain yields and WUE. Shijiazhuang 8 displayed a higher grain yield and WUE than Yanmai 20 under drought stress, and throughout the different stages of growth, the leaves exhibited a lower net photosynthetic rate ( ), stomatal conductance ( ) and transpiration ( ) under drought stress. Furthermore, Shijiazhuang 8 which maintained relatively higher, , and under water stress, maintained higher values of WUE than Yanmai 20. Under the severe stress treatments, some varieties showed an increase in the concentration of intercellular CO ( ), indicating an inhibition of photosynthetic activity due to non-stomatal effects. Overall, we conclude that the genotypic differences in the photosynthetic response could be useful for mapping the photosynthetic traits that promote tolerance to drought. We recommend that mild water stress (65–70% water field capacity) be considered for irrigation scheduling in winter wheat under conditions of water limitation.