Discriminant analysis is an important method in multivariable statistic analysis to show what type an individual should belong to. Based on actual field photosynthetic value set obtained from our research platform, North East China Transect (NECT), a new approach, developed from the concept and principle of discriminant analysts, was proposed to distinguish C3 and C4 plants. Indices related to plant photosynthetic capacity measured by an LCA4 photosynthesis system were selected to build the discriminant model which is based on four related parameters: net photosynthetic rate, transpiration rate, stomatal conductance, and difference in temperature between leaf surface and atmosphere. Compared with other approaches, the present one is fast, straightforward, and efficient. and H. P. Tang, X. S. Zhang.
Leaf anatomy and eco-physiology of Elymus repens, a temperate loess grassland species, were determined after seven years of exposure to 700 μmol (CO2) mol-1 (EC). EC treatment resulted in significant reduction of stomatal density on both surfaces of couch-grass leaves. Thickness of leaves and that of the sclerenchyma tissues between the vessels and the adaxial surfaces, the area of vascular bundle, and the volumes of phloem and tracheary increased at EC while abaxial epidermis and the sclerenchyma layer between the vessel and the abaxial surface were thicker at ambient CO2 concentration (AC). Stomatal conductance and transpiration rates were lower in EC, while net CO2 assimilation rate considerably increased at EC exposure. Contents of soluble sugars and starch were higher in EC-treated couch-grass leaves than in plants grown at AC. and A. I. Engloner ... [et al.].
Biomass, leaf water potential (Ψl), net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), leaf to air temperature difference (Tdiff), and instantaneous water use efficiency (WUE) were measured in the seedlings of Dalbergia sissoo Roxb. grown under irrigation of 20 (W1), 14 (W2), 10 (W3), and 8 (W4) mm. Treatments were maintained by re-irrigation when water content of the soil reached 7.4% in W1, 5.6% in W2, 4.3% in W3, and 3.2% in W4. Seedlings in a control (W5) were left without irrigation after maintaining the soil field capacity (10.7%). Seedlings of W1 had highest biomass that was one tenth in W5. Biomass allocation was highest in leaf in W2 and in root in W4 and W5 treatments. Difference between predawn leaf water potential (ΨPd) and midday (Ψmid) increased with soil water stress and with vapour pressure deficit (VPD) in April and May slowing down the recovery in plant leaf water status after transpiration loss. PN, E, and gs declined and Tdiff increased from W1 to W5. Their values were highly significant in April and May for the severely stressed seedlings of W4 and W5. PN increased from 08:00 to 10:00 and E increased until 13:00 within the day for most of the seedlings whereas gs decreased throughout the day from 08:00 to 17:00. PN and E were highest in March but their values were low in January, February, April, and May. Large variations in physiological variables to air temperature, photosynthetically active radiation, and vapour pressure deficit (VPD) indicated greater sensitivity of the species to environmental factors. WUE increased from W1 to W2 but decreased drastically at high water stress particularly during hot summer showing a kind of adaptation in D. sissoo to water stress. However, low biomass and reduced physiological functions at <50% of soil field capacity suggest that this species does not produce significant biomass at severe soil water stress or drought of a prolonged period. and B. Singh, G. Singh.
Variables of gas exchange of flag leaves and grain yield potentials of five representative winter wheat (Triticum aestivum L.) cultivars varied greatly across different development stages under the same management and irrigation. The cultivars with high yield potential had higher net photosynthetic rate (PN), PPFD (photosynthetic photon flux density) saturated photosynthetic rate (Psat), stomatal conductance (gs), and maximum apparent quantum yield of CO2 fixation (Φm,app) than those with low grain yield, but their dark respiration rate (RD) and compensation irradiance (Ic) were remarkably lower. Compared with overall increase of yield potential of 71 % from low yield cultivars to high yield ones, PN, Psat, Φm,app, and gs were 13, 19, 57, and 32 % higher, respectively; but RD and Ic decreased by 19 and 76 %, respectively. Such difference was evidently large during anthesis stage (e.g., PN by 33 %), which indicated that this period could be the best for assisting further selection for better cultivars. However, transpiration rate (E) and water use efficiency (WUE) differed only little. At different development stages, especially at anthesis, PN and Psat were positively correlated with Φm,app, gs, and yield potential, and negatively correlated with RD and Ic. Thus the high-yield-potential winter wheat cultivars possess many better characters in photosynthesis and associated parameters than the low-yield cultivars. and G. M. Jiang ... [et al.].
Diurnal courses in net photosynthetic rate (PN), stomatal conductance (gs), leaf water potential (ψ), internal CO2 concentration (ci), and water use efficiency (WUE) were studied as season progressed, in relation to environmental factors in field grown Prunus amygdalus. In sun leaves PN reached maximum between 09:00 to 11:00 h and subsequently declined when high temperature and low humidity occurred. An increase was observed late in the afternoon. A decrease in gs and ψ was found as season progressed in both years of measurements. In periods of high evaporative demand, ψ was very low, however, it did not explain the reductions of PN in all the three periods (spring, early and late summer). Midday depression of PN and gs seemed to be related with leaf temperature (Tl) and high irradiance. Increase in ci and F0 and decrease in Fv/Fm found between 12:00 and 14:00 h corresponded to the decrease in PN. Therefore, a transient modification of photosynthetic machinery might be considered. WUE was negatively correlated with vapour pressure difference of leaf to air, that decreased during the day. The September values, higher than in the previous months, were due to the lower seasonal decreases in PN than in gs. and M. C. Matos ... [et al.].
Diurnal and seasonal trends in net photosynthetic rate (PN), stomatal conductance (g), transpiration rate (E), vapour pressure deficit, temperature, photosynthetic photon flux density, and water use efficiency (WUE) were compared in a two-year-old Dalbergia sissoo and Hardwickia binata plantation. Mean daily maximum PN in D. sissoo ranged from 21.40±2.60 µmol m-2 s-1 in rainy season I to 13.21±2.64 µmol m-2 s-1 in summer whereas in H. binata it was 20.04±1.20 µmol m-2 s-1 in summer and 13.64±0.16 µmol m-2 s-1 in winter. There was a linear relationship between daily maximum PN and gs in D. sissoo but there was no strong linear relationship between PN and gs in H. binata. In D. sissoo, the reduction in gs led to a reduction in both PN and E enabling the maintenance of WUE during dry season thereby managing unfavourable environmental conditions efficiently whereas in H. binata, an increase in gs causes an increase of PN and E with a significant moderate WUE. and S. G. Saraswathi, K. Paliwal.
The effects of drought stress induced by polyethylene glycol, PEG (molecular mass 6000) on some ecophysiological characteristics of two wild pistachio species, Mastic and Khinjuk (P. mutica and P. khinjuk) selected as root stocks for production of edible pistachio trees (P. vera) in Iran and Turkey, were studied. Net photosynthetic rate (PN), stomatal conductance (gs), chlorophyll (Chl) fluorescence parameters, leaf water potential (Ψ1), leaf osmotic potential (Ψπ), leaf osmotic adjustment (ΔΨπ), and Chl a and b were measured. All parameters were influenced by increase in concentra-tion of PEG in the nutrient solutions. PN, gs, and Chl a were significantly higher in P. mutica than in P. khinjuk but, compared to the control treatment, P. khinjuk showed a higher resistance to drought stress than P. mutica. and A. Ranjbarfordoei ... [et al.].
We compared the effect of elevated temperature on morphological development, biomass accumulation and allocation, and gas exchange of three dominant plants (Caragana intermedia Kuanget H.C. Fu, Hedysarum mongolicum Turcz., and Artemisia ordosica Krasch.) growing in Chinese Maowusu sandland. Plants were grown in two temperature chambers (25/20, 28/23 °C, day/night) during 60 d. Tree height, number of leaves, and leaf area were increased in C. intermedia and H. mongolicum seedlings, while in A. ordosica temperature only affected tree height. Elevated temperature increased biomass and reduced the root : shoot ratio in C. intermedia and H. mongolicum seedlings, but not in A. ordosica seedlings. The net photosynthetic rate (PN) and transpiration rate (E) were increased at days 40 and 60 in C. intermedia and H. mongolicum seedlings, while in A. ordosica seedlings no significant effects on E were observed, and PN was increased only at day 60. Water use efficiency (WUE) was reduced at days 40 and 60 in H. mongolicum seedlings, and at day 60 in C. intermedia seedlings. No temperature effect on WUE was observed in A. ordosica seedlings. These different responses indicate that climate change could alter plant communities in Maowusu sandland. and Chun-Wang Xiao, Guang-Sheng Zhou, R. Ceulemans.
Species composition and photosynthetic characteristics of dominant species of ungrazed plot (UG), overgrazed plot (OG), and restored grazed plot (RG) were determined in the Xilin River Basin, Inner Mongolia, China. Both heavily grazing and restoration significantly affected the composition of different species and life forms. Leymus chinensis, Stipa grandis, and Cleistogenes polyphylla, three dominant perennial grasses in UG plot, contributed 58.9 % aboveground biomass to that of whole community, and showed higher net photosynthetic rate (PN), transpiration rate (E), and intrinsic water-use efficiency (WUE). In OG plot, relative biomass of L. chinensis and S. grandis significantly decreased, while relative biomass of three shrubs/sub-shrubs, Caragana microphylla, Artemisia frigida, and Kochia prostrata, obviously increased. Heavy grazing significantly decreased PN, E, and WUE of L. chinensis and S. grandis, while shrubs/sub-shrubs showed significantly higher photosynthetic activity and WUE than the grasses. After 18-year restoration, photosynthetic activities of L. chinensis and S. grandis were significantly higher than those in the OG plot. The proportion of L. chinensis, S. grandis, and C. microphylla significantly increased, and relative biomass of C. polyphylla, A. frigida, and K. prostrata markedly declined in RG plot. We found close relationships between physiological properties of species and their competitive advantage in different land use types. Higher photosynthetic capability means more contribution to total biomass. The variations in physiological characteristics of plants could partly explain the changes in species composition during degrading and restoring processes of Inner Mongolia typical steppes. and S. P. Chen ... [et al.].
Photosynthetic and growth characteristics of Mosla chinensis and M. scabra were compared at three irradiances similar to shaded forest understory, forest edge, and open land. At 25 % full ambient irradiance, M. chinensis and M. scabra had similar photosynthetic characteristics, but saturation irradiance, compensation irradiance, and apparent quantum yield of M. chinensis were higher than those of M. scabra at full ambient irradiance and 70 % full ambient irradiance. At the same irradiance treatment, specific leaf area and leaf area ratio of M. chinensis were lower than those of M. scabra. Photon-saturated photosynthetic rate and water use efficiency of M. chinensis, however, were not significantly higher than those of M. scabra, and the leaf area and total biomass were lower than those of M. scabra. As a sun-acclimated plant, the not enough high photosynthetic capacity and lower biomass accumulation may cause that M. chinensis has weak capability to extend its population and hence be concomitant in the community. and J.-X. Liao ... [et al.].