Dark respiration rate in the night (R D) was measured in five-year-old Scots pine (Pinus sylvestris L.) trees grown for two years under ambient (AC) and elevated (AC + 400 µmol mol-1 = EC) CO2 concentrations in open top chambers. Two needle age classes (i.e., current-year and one-year-old) were measured at AC and EC in both AC- and EC-grown pines. Additionally different chemical characteristics were determined on the needles, such as nitrogen (N), carbon (C), starch, and soluble sugar concentrations as well as specific leaf area. The direct, short-term and indirect, long-term effects of EC on R D for the two needle age classes were examined. R D was expressed on a per needle area, needle mass, N, C, and C/N bases. Direct effects were only pronounced in the AC treatment where inhibition of R D was found at EC in both current- and one-year-old needles. Indirect effects were only significant in one-year-old needles where a decrease was found in the EC grown trees as compared with AC ones when R D was expressed per unit needle mass, C, or C/N. R D per unit needle area and needle N were not sensitive to long-term EC, in any needle age class. Long-term EC treatment also influenced the response of the two needle age classes. One-year-old needles from the EC treatment had significantly lower R D than current-year needles, but no such response was observed in the AC treatment. Our experiment re-emphasised the importance of expressing R D on different bases for a correct interpretation of the responses to EC. Moreover, we showed that different needle age classes can respond differently to a CO2 enrichment. and M. E. Jach, R. Ceulemans.
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.].
Clover seedlings were grown at different nitrogen concentrations (5, 10, 15, 20, 25 mM NO3 -, i.e. N5 to N25) and two irradiances, I (200 and 400 µmol m-2 s-1 of photon flux density, i.e. I 200 and I 400). Net photosynthetic rate (PN), photosynthetic nitrogen use efficiency (PNUE), leaf chlorophyll (Chl) content, maximum photochemical efficiency (Fv/Fm), and actual photochemical efficiency of photosystem 2 (PS2) (ΦPS2) increased from N5 to N15 and decreased with N15 to N25. P N, PNUE, and ΦPS2 were higher at I 400 than at I 200, but Fv/Fm and leaf Chl contents at I 400 were lower than at I 200. The effects of the N and I on specific leaf area (SLA) and N contents per unit dry mass (Nm) were similar, the SLA and Nm increased from N5 to N25 and they were higher at I 200 than at I 400. The nitrogen contents per unit area (Na) increased from N5 to N20, but decreased from N20 to N25. The Na was higher at I 200 than at I 400 when Trifolium repens grew at N5 and N10, but it was higher at I 400 than at I 200 at N15 to N25. and H. An, Z. P. Shangguan.
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.].