Anthropogenic activities are changing global precipitation regimes and result in many middle latitude arid and semiarid regions experiencing less precipitation and more extreme weather events. However, little is known about the response of active ingredient accumulation in the medicinal herb Plantago depressa Willd. Therefore, we carried out a greenhouse experiment in order to study effect of control (CK, normal water supply equal to 309 mm per four months), -30 (-WS) and +30% (+WS) of the control water supply on the photosynthesis (PN), C/N ratio, and plantamajoside accumulation in P. depressa. Our results showed that compared with the-WS and CK treatments, the +WS treatment significantly enhanced biomass, the C/N ratio, plantamajoside concentration, yield in shoots and roots, and PN, but declined the N concentration in shoots and roots. The plantamajoside concentration was positively correlated with PN, the soluble sugar content, and the C/N ratio, but negatively correlated with the N concentration. Our results suggested that, under experimental conditions, +WS increased the C/N ratio and promoted the plantamajoside accumulation of P. depressa., Z. Li, W. Bai, L. Zhang, L. Li., and Obsahuje bibliografii
Our experiment was carried out in order to explore effects of plant growth regulators (PGR; thidiazuron, paclobutrazol, and ascorbic acid) on physiological traits of wheat genotypes under water surplus and deficit conditions. Study revealed that relative water content, membrane stability index, chlorophyll content, photosynthetic rate (PN), and maximal quantum yield of PSII improved with PGRs application across the genotypes both under irrigation and water stress. The response of HD 2733 genotype was more positive toward PGRs treatment as compared to other genotypes under water stress. Higher PN and chlorophyll contents were observed in HD 2987 followed by C 306 genotype under water-stress conditions. Moreover, Rubisco small subunit (SSU) expression was lower in wheat genotypes under water stress as compared to irrigated conditions. Application of PGRs led to upregulation of SSU under water stress, while no significant change was found in Rubisco level and activity under irrigated condition in dependence on PGRs treatments. Yield-related traits showed also significant reduction under water-stress conditions, while application of PGRs enhanced the yield and its components. Results indicated that the PGRs exhibited a positive interaction and synergetic effect on water stressed wheat plants in terms of photosynthetic machinery and yield., S. K. Dwivedi, A. Arora, V. P. Singh, G. P. Singh., and Obsahuje bibliografii
In order to elucidate the drought resistance and high-yield mechanism of hybrid millet, we studied the influence of drought stress on the photosynthetic characteristics and dry matter accumulation. Our results revealed that drought stress caused lesser reduction in the net photosynthetic rate, maximal quantum yield of PSII photochemistry, excitation energy capture efficiency of PSII reaction centers and in the yield of hybrid millet compared to normal millet. When drought stress occurred in the jointing stage, the percentage decrease of PN, Fv/Fm, Fv′/Fm′, and the yield of Zhangzagu3 cultivar compared to control were 27.9%, 2.6%, 25. 5%, and 1.9%, respectively, the percentage decrease of Zhangzagu5 were 37.6%, 3.9%, 28.3%, and 16.7%, respectively, the decrease percentage of Datong29 were 60.1%, 6.4%, 4%, and 23.4%, respectively. Hybrid millet showed the similar reduction in the parameters referred above, when drought stress occurred at the heading stage, but the percentage decrease was much higher than that at the jointing stage. We concluded that hybrid millet showed higher drought resistance than normal millet., H. B. Lu, Y. M. Qiao, X. C. Gong, H. Q. Li, Q. Zhang, Z. H. Zhao, L. L. Meng., and Obsahuje bibliografii
Influence of different phosphorus concentrations was studied in four rice varieties (Akhanphou, MTU1010, RP BIO 226, and Swarna) differing in their tolerance to low phosphorus. There was an increase in shoot and root dry mass with the increase in phosphorus concentration. At the low phosphorus concentration at both tillering and reproductive stages, Swarna, followed by Akhanphou, recorded maximum biomass for both roots and shoots, while the minimum was observed in RP BIO 226. Reduction in photosynthetic rate, stomatal conductance, transpiration rate, and internal CO2 concentration at low phosphorus concentrations were observed at both tillering and reproductive stages in all the genotypes. In low phosphorus, maximum photosynthetic rate was found in Swarna followed by Akhanphou. Phosphorus deficiency did not alter the maximum efficiency of PSII photochemistry, however, there was a reduction in effective PSII quantum yield, electron transport rate, and coefficient of photochemical quenching, while the coefficient of nonphotochemical quenching was higher in the low phosphorus-treated plants. Prolonged exposure to excessive energy and failure to utilize the energy in carbon-reduction cycle induced the generation of reactive oxygen species, which affected PSII as indicated by the fluorescence traits. The reduction was less severe in case of Swarna and Akhanphou. The activities of superoxide dismutase, peroxidase, and catalase increased in roots under low phosphorus concentration indicating that photoprotective mechanisms have been initiated in rice plants in response to phosphorus deficiency. Comparatively, Swarna and Akhanphou exhibited a higher biomass, higher photosynthetic rate, and better reactive oxygen species-scavenging ability which conferred tolerance under low phosphorus conditions., N. Veronica, D. Subrahmanyam, T. Vishnu Kiran, P. Yugandhar, V. P. Bhadana, V. Padma, G. Jayasree, S. R. Voleti., and Obsahuje bibliografii
Plant invasions may be limited by low radiation levels in ecosystems such as forests. Lantana camara has been classified among the world's 10 worst weeds since it is invading many different habitats all around the planet. Morphological and physiological responses to different light fluxes were analyzed. L. camara was able to acclimate to moderately shaded environments, showing a high phenotypic plasticity. Morphological acclimation to low light fluxes was typified by increasing leaf size, leaf biomass, leaf area index and plant height and by reduced stomatal density and leaf thickness. Plants in full sunlight produced many more inflorescences than in shaded conditions. Physiological acclimation to low radiation levels was shown to be higher stomatal conductance, higher net photosynthetic rates and higher efficiency of photosystem II (PSII). L. camara behaves as a facultative shade-tolerant plant, being able to grow in moderately sheltered environments, however its invasion could be limited in very shady habitats. Control efforts in patchy environments should be mainly directed against individuals in open areas since that is where the production of seeds would be higher and the progress of the invasion would be faster. and J. Carrión-Tacuri ... [et al.].
Tropical rainforest trees adjust leaf traits during ontogeny to cope with changes in the physical environment and maximize their carbon uptake. The aim of this study was to determine the plasticity index (PI) of leaf traits in understory and canopy leaves of six Amazonian tree species. In four of the six species the PI of leaf traits varied within species, and in four of the ten leaf traits assessed, the PI differed between species. The greatest PI values were found for stomatal density (Ds) and CO2-saturated photosynthesis, and the lowest ones were found for stomatal size, and leaf thickness. Despite the differences in PI values within species, the mean PI was similar in all the six species. As the saplings grow toward the canopy, the strategy to increase carbon uptake involves increasing Ds and leaf nitrogen and reducing stomatal size., R. A. Marenco, M. A. B. Camargo, S. A. Antezana-Vera, M. F. Oliveira., and Obsahuje seznam literatury
Using measures of gas exchange and photosynthetic chain activity, we found some differences between grapevine inflorescence and leaf in terms of photosynthetic activity and photosynthesis regulations. Generally, the leaf showed the higher net photosynthesis (PN) and lower dark respiration than that of the inflorescence until the beginning of the flowering process. The lower (and negative) PN indicated prevailing respiration over photosynthesis and could result from a higher metabolic activity rather than from a lower activity of the photosynthetic apparatus. Considerable differences were observed between both organs in the functioning and regulation of PSI and PSII. Indeed, in our conditions, the quantum yield efficiency and electron transport rate of PSI and PSII were higher in the inflorescence compared to that of the leaf; nevertheless, protective regulatory mechanisms of the photosynthetic chain were clearly more efficient in the leaf. This was in accordance with the major function of this organ in grapevine, but it highlighted also that inflorescence seems to be implied in the whole carbon balance of plant. During inflorescence development, the global PSII activity decreased and PSI regulation tended to be similar to the leaf, where photosynthetic activity and regulations remained more stable. Finally, during flowering, cyclic electron flow (CEF) around PSI was activated in parallel to the decline in the thylakoid linear electron flow. Inflorescence CEF was double compared to the leaf; it might contribute to photoprotection, could promote ATP synthesis and the recovery of PSII., M. Sawicki, B. Courteaux, F. Rabenoelina, F. Baillieul, C. Clement, E. Ait Barka, C. Jacquard, N. Vaillant-Gaveau., and Obsahuje bibliografii
Tropical canopy tree species can be classified into two types by their heterobaric and homobaric leaves. We studied the relation between both leaf types and their water use, together with the morphological characteristics of leaves and xylem, in 23 canopy species in a tropical rain forest. The maximum rates of photosynthesis and transpiration were significantly higher in heterobaric leaf species, which also underwent larger diurnal variations of leaf water potential compared to homobaric leaf species. The vessel diameter was significantly larger and the stomatal pore index (SPI) was significantly higher in heterobaric than that in homobaric leaf species. There was a significant positive correlation between the vessel diameter, SPI, and maximum transpiration rates in all the studied species of both leaf types. However, there was no significant difference in other properties, such as leaf water-use efficiency, leaf mass per area, leaf nitrogen content, and leaf δ13C between heterobaric and homobaric leaf species. Our results indicate that leaf and xylem morphological differences between heterobaric and homobaric leaf species are closely related to leaf water-use characteristics, even in the same habitat: heterobaric leaf species achieved a high carbon gain with large water use under strong light conditions, whereas homobaric leaf species can maintain a high leaf water potential even at midday as a result of low water use in the canopy environment., Y. Inoue, T. Kenzo, A. Tanaka-Oda, A. Yoneyama, T. Ichie., and Obsahuje bibliografii
The impact of a heterogeneous distribution of actinic light within a leaf chamber for photosynthetic measurements by gas exchange on the photosynthesis-irradiance relationship was investigated. High-resolution light distributions were measured over the area of a commercially available clamp-on leaf chamber equipped with build-in red and blue LEDs, as well as over the area of a custom-made leaf chamber with external light source, using a low-cost digital camera and freely available software. The impact of the measured heterogeneity on the photosynthesis-irradiance response curve was calculated for two realistic scenarios. When the average light intensity over the leaf chamber area was estimated accurately, heterogeneity had minor effects on the photosynthesis-irradiance response curve. However, when the irradiance was measured in the chamber centre, which is common practice, and assumed to be homogeneous, for both leaf chambers the photosynthesis-irradiance response curve was subject to considerable error and led to serious underestimation of the light-limited quantum yield of photosynthesis. Additionally, mixed light sources with different heterogeneity patterns per light source, such as in the clamp-on leaf chamber, potentially increase errors due to heterogeneous physiological responses to light spectrum. High-resolution quantification of the leaf-chamber light distribution enables calculation of the correct average light intensity and already resolves the most pressing problems associated with heterogeneity. To exclude any light-distribution related errors in
gas-exchange measurements a leaf chamber and actinic irradiance source design with a homogeneous light distribution is an absolute requirement. and S. W. Hogewoning ...[et al.].
Although maize (Zea mays L.) plants utilize light efficiently, the expression of high light-efficient genes and stomatal factors is regulated by light conditions and affects photosynthesis of plants. In this study, we investigated the effects of different light qualities on the expression of the photosynthetic genes, such as pep1, pdk1, ZmSTOMAGEN, and psad1, and on stomatal function in maize seedlings. For both maize genotypes, Zhengdan 958 and Xianyu 335, light with wavelengths shorter than 490 nm enhanced the expression of pdk1 and ZmSTOMAGEN, whereas the expression of pdk1 positively correlated with ZmSTOMAGEN. Light with wavelengths longer than 630 nm or shorter than 490 nm (band pass filter) increased the expression of pep1 and psad1. Although the expression of four genes in Zhengdan 958 was significantly higher than that of Xianyu 335, changes in the expression of ZmSTOMAGEN, pdk1, or pep1 exerted no significant influence on stomatal function and photosynthetic rate. Our results suggest that light with wavelengths shorter than 490 nm promoted the expression of stomatal proteins and pdk1, facilitated the absorption of inorganic elements, and contributed to stomatal function in photosynthesis. Meanwhile, light with wavelengths longer than 630 nm inhibited the expression of pep1 and pdk1. Light with wavelengths longer than 630 nm or shorter than 490 nm promoted the expression of pep1, pdk1, and psad1., T. D. Liu, X. W. Zhang, Y. Xu, S. Q. Liu, X. W. Chen., and Obsahuje bibliografii