The combined effects of water stress (WS) and low irradiance (LI) on growth, photosynthesis, osmotic adjustment, and lipid peroxidation were studied in dragon spruce (Picea asperata Mast.) seedlings grown under two water treatments (well watered, 100 % of field capacity, and water stressed, 30 % of field capacity) and two irradiances (HI, 100 % of full sunlight and LI, 15 % of full sunlight). WS reduced growth, chlorophyll (Chl) a and b contents, net photosynthetic rate, transpiration rate, stomatal conductance, and effective quantum yield of photosystem 2 (Y) but increased free proline and malondialdehyde contents. LI increased Chl contents and decreased Y, photochemical quenching (qP), and non-photochemical quenching (qN) under both water treatments. Hence the seedlings in the understory were more sensitive to drought than to LI. and Y. Yang ... [et al.].
We related leaf physiological traits of four grassland species (Poa pratensis, Lolium perenne, Festuca valida, and Taraxacum officinale), dominant in a Mediterranean grassland, to their origin and success at community level. From early May to mid-June 1999, four leaf samplings were done. Species originating from poor environments (P. pratensis, F. valida) had low carbon isotope discrimination (Δ), specific leaf area (SLA), leaf water and mineral contents, and net photosynthetic rate on mass basis (Pmass) but high chlorophyll content. The reverse traits were evident for the fast-growing species (L. perenne, T. officinale). Under the resource-limiting conditions (soil nitrogen and water) of the Mediterranean grassland, the physiological traits of P. pratensis and F. valida showed to be more adapted to these conditions leading to high species abundance and dominance. and J. T. Tsialtas, T. S. Pritsa, D. S. Veresoglou.
Specific leaf area (SLA) is a key trait to screen plants for ecological performance and productivity; however, the relationship between SLA and photosynthesis is not always up-scalable to growth when comparing multiple species with different life cycles. We explored leaf anatomy in annual and perennial species of Physaria, and related it to photosynthesis and water loss. The annual Physaria gracilis had higher SLA, thinner leaves, and lower investment in protective tissues, than perennial P. mendocina. Physaria angustifolia (annual), and P. pinetorum (perennial) showed intermediate values. Both perennials had a thicker palisade and high photosynthesis, relative to annuals. The larger leaf veins of perennials should allow high water availability to the mesophyll. The thicker palisade should determine high resistance to water flow and help explain their high water-use efficiency. These leaf functions reflect the construction of long-lived leaves that efficiently use resources under environmental limitations of arid environments., L. Gonzalez-Paleo, D. A. Ravetta., and Obsahuje bibliografii
Cuttings of Populus cathayana were exposed to three different alkaline regimes (0, 75, and 150 mM Na2CO3) in a semicontrolled environment. The net photosynthesis rate (PN), mesophyll conductance (gm), the relative limitations posed by stomatal conductance (Ls) and by mesophyll conductance (Lm), photosynthetic nitrogen-use efficiency (PNUE), carbon isotope composition (δ13C), as well as specific leaf area (SLA) were measured. PN decreased due to alkaline stress by an average of 25% and gm decreased by an average of 57%. Alkaline stress caused an increase of Lm but not Ls, with average Ls of 26%, and Lm average of 38% under stress conditions. Our results suggested reduced assimilation rate under alkaline stress through decreased mesophyll conductance in P. cathayana. Moreover, alkaline stress increased significantly δ13C and it drew down CO2 concentration from the substomatal cavities to the sites of carboxylation (Ci-Cc), but decreased PNUE. Furthermore, a relationship was found between PNUE and Ci-Cc. Meanwhile, no correlation was found between δ13C and Ci/Ca, but a strong correlation was proved between δ13C and Cc/Ca, indicating that mesophyll conductance was also influencing the 13C/12C ratio of leaf under alkaline stress. and G. Xu ... [et al.].
Seedling recruitment is a critical developmental stage in regeneration of plant populations under Mediterranean conditions that strongly depends on water availability. Seed mass and relative growth rate (RGR) may affect the early establishment of seedlings through different physiological processes. Here, we examined the effects of the seed mass and carbon balance on seedling growth under two water regimes in Rhamnus alaternus L. and Rhamnus ludovici-salvatoris, two Mediterranean shrubs, showing a different ability to recruit seedlings. Plant water consumption and biomass accumulation (ΔB) were measured during three periods of the growth in order to estimate water use efficiency (WUE), RGR, and its components. Additionally, net photosynthesis and leaf, stem, and root respiration were measured in plants grown in pots well watered and under progressive drought. Rhamnus alaternus showed the higher seed mass, ΔB, and plant WUE than that of R. ludovici-salvatoris in all periods and water regimes. The higher RGR of R. alaternus was observed during the first and the second period, but the reverse trend was registered during the third period as a consequence of the higher initial biomass of R. alaternus. Also, R. alaternus showed a higher specific leaf area and estimated carbon balance than that of R. ludovicisalvatoris. The observed differences in ΔB, estimated carbon balance, seed mass, and WUE between both species could explain their different distribution and ability to recruit seedlings under natural conditions., H. El Aou-Ouad, I. Florez-Sarasa, M. Ribas-Carbó, J. Flexas, H. Medrano, J. Gulías., and Obsahuje seznam literatury
Variations in leaf gas-exchange characteristics, leaf pigment content, and other important leaf traits were investigated in seven wild Oryza species, five hybrids, and five improved varieties. The significant variations were observed in photosynthetic pigment contents amongst different species of Oryza. The mean chlorophyll (Chl) content was higher in O. sativa (varieties and hybrids), while O. eichengeri showed the lowest Chl content. The mean carotenoid (Car) content in O. sativa (varieties and hybrids) was higher than in other wild rice species. O. eichengeri and O. barthii had significantly lower Car contents than other rice species. Significant differences were noticed in the rate of photosynthesis (PN), stomatal conductance (gs), transpiration rate (E), internal CO2 concentration (Ci), specific leaf mass (SLM), and leaf thickness amongst different Oryza species. The mean PN was the highest in O. nivara followed by O. eichengeri. The mean PN was the lowest in O. glumaepatula, which was lower than that of cultivated varieties and hybrids of O. sativa. High rates of photosynthesis were observed in O. nivara (ACC. No. CR 100097), O. rufipogon (ACC.No. CR 100267), and O. nivara (ACC.No. CR 100008). The O. nivara and O. rufipogon genotypes with high PN might be used in rice improvement programmes for an increase of leaf photosynthesis in rice. Multiple correlations performed between different gas-exchange characteristics and other physiological traits revealed that the rate of photosynthesis was not dependent on the leaf pigment content or the leaf thickness. A strong positive correlation between PN and the PN/Ci ratio, which represents the carboxylation efficiency, indicated that the observed variation in PN was not based on pigment content or other leaf traits. and T. V. Kiran ... [et al.].
Leaf traits have long been recognized as influential factors in the acquisition and processing of resources by plants. However, there is less knowledge of between-species variations in seasonal changes in leaf traits and trait interrelationships. Therefore, we examined variations in leaf area (LA), dry biomass (DM), specific leaf area (SLA), and leaf gas-exchange parameters in one non-native and seven native tree species under field environmental conditions, in a karst area in China subjected to desertification. Measurements were taken three times during the growing season. The results show that the seven native trees had higher LA, DM, and water-use efficiency (WUE) than the non-native Cinnamomum camphora. In contrast, all the native tree species except Ligustrum lucidum had lower photosynthetic rates (PN) than the non-native species. In all species, the relationship between LA and DM was less variable than the relationship between SLA and LA. However, leaves of the non-native C. camphora and native species Sterculia lanceolata, Cleidiocarpon cavalerei and Cyclobalanopsis glauca were highly sensitive to seasonal conditions, leaves of Sapindus mukorossi and Ligustrum lucidum were less sensitive to seasonal changes, and leaves of Syzygium cumini and Cephalomappa sinensis were insensitive. An understanding of leaf traits will aid the selection of suitable species for land restoration. and L.-Y. Wei ... [et al.].