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12. Seasonal and interannual variations of ecosystem photosynthetic features in an alpine dwarf shrubland on the Qinghai-Tibetan Plateau, China
- Creator:
- Li, H. Q., Zhang, F. W., Li, Y. N., Cao, G. M., Zhao, L., and Zhao, X. Q.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, fenologie, photosynthesis, phenology, Čína západní, Tibet (Čína), China, Western, ecosystem photosynthetic parameters, eddy covariance technique, leaf area index, rectangular hyperbolic light response, 2, and 581
- Language:
- Multiple languages
- Description:
- Ecosystem photosynthetic characteristics are of utmost importance for the estimation of regional carbon budget, but such characteristics are not well understood in alpine regions. We collected CO2 flux data measured by eddy covariance technique over an alpine dwarf shrubland on the Qinghai-Tibetan Plateau during years 2003-2010; and we quantified the temporal patterns of ecosystem apparent quantum yield (a), saturated photosynthetic rate (Pmax), and ecosystem dark respiration (RDe). Results showed that the strong seasonality of a and RDe was driven mainly by air temperature (Ta), whereas that of Pmax was much more determined by leaf area index rather than abiotic factors. Diurnal thermal fluctuation inhibited significantly the daytime photosynthetic capacity. Stepwise regression revealed that the seasonal deviations of a, Pmax, and RDe were significantly controlled by Ta. The annual a was regulated mainly by annual growing season Ta, which indicated that the response of ecosystem a was instant. The annual variations of Pmax correlated positively with soil temperature 5 cm below ground (Ts) of the annual nongrowing season and those of RDe related negatively with the annual nongrowing season precipitation. We suggested that a lagged response regulated the annual Pmax and the annual RDe. Annual deviations of a and RDe were both significantly controlled by annual Ts, and those of Pmax were marginally determined by annual PPFD. Thus, the future warming scenario, especially significant for nongrowing seasonal warming in the Qinghai-Tibetan Plateau, would favor ecosystem photosynthetic capacity in the alpine dwarf shrubland., H. Q. Li, F. W. Zhang, Y. N. LI, G. M. Cao, L. Zhao, X. Q. Zhao., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
13. Seasonal water-use efficiency and chlorophyll fluorescence response in alpha grass (Stipa tenacissima L.) is affected by tussock size
- Creator:
- Ramírez, D. A. , Valladares, F., Domingo, F., and Bellot, J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- leaf area index, net photosynthetic rate, photoinhibition, photosystem 2, plant size, semiaridity, stomatal conductance, transpiration rate, and water stress
- Language:
- Multiple languages
- Description:
- Twelve randomly chosen Stipa tenacissima L. individuals were grouped into three tussock size classes, small (ST), medium (MT), and large (LT) with 5.6±0.8, 34.1±4.2, and 631.9±85.8 g of dry green foliar matter, respectively, in three plots with different S. tenacissima cover. Instantaneous (WUEi) and long-term (WUEl) water-use efficiencies were measured in two seasons of contrasting volumetric soil water content (early winter 21.0±0.8 % and summer 5.8±0.3 %). Maximum photochemical efficiency of photosystem 2 and stomatal conductance in summer assessed the extent of water and irradiance stress in tussocks of different size. WUEi was lower in MT and ST “water spender” strategies than in LT during the high water-availability season. In summer net photosynthetic rate and WUEi were higher and photoinhibition was lower in LT than in MT and ST. Significant spatial variability was found in WUEi. Water uptake was competitive in stands with denser alpha grass and more water availability in summer, reducing their WUEi. However, WUEl showed a rising tendency when water became scarce. Thus it is important to explicitly account for plant size in ecophysiological studies, which must be combined with demographic information when estimating functional processes at stand level in sequential scaling procedures. and D. A. Ramírez ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
14. Structural and ecophysiological plasticity of some evergreen species of the mediterranean maquis in response to climate
- Creator:
- Gratani, L.
- Format:
- Type:
- model:internalpart and TEXT
- Subject:
- Arbutus unedo L., Cistus incanus L., leaf area index, leaf thickness, net photosynthetic rate, Phillyrea latifolia L., Pistacia lentiscus L,, Quercus ilex L., stomatal conductance, and transpiration
- Language:
- Multiple languages
- Description:
- The most representative evergreen shrub species growing in the low mediterranean maquis modified their leaf characteristics during the year, but the response to climate varied among the species. The reál sclerophyllous species, Quercus ilex L., Phillyrea latifolia and Pistacia lentiscus, showed a convergence in higher leaf thickness and lower net photosynthetic rate (P^) compared with Arhuíus unedo L. and Cistus incanus L. Under summer stress they maintained a substantial positive carbon balance. Pistacia was one of the most tolerant species to the drought, it maintained a substantial positive balance over a wide range in temperature. Arhutus and Cistus had relatively thin leaves with a higher succulence index and higher ihe more characteristic sclerophyllous species. The superiority of Cistus in carbon uptake over all the spacies was maintained throughout most of the year by its morphological leaf properties: low leaf thickness, high chlorophyll contents. Besides, Cistus shed most of its leaves before summer, thus reducing its evaporative surface.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
15. The photosynthetic efficiency of some elite rice hybrids and restorers
- Creator:
- Baig, M. J., Swain, P., and Murty, K. S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- cultiivars, growth stages, heterosis, leaf area index, maintenance respiration, net photosynthetic rate, and Oryza sativa
- Language:
- Multiple languages
- Description:
- At the vegetative growth stage (40 d), the mean photosynthetic rate (PN) and canopy photosynthesis (PN × LAI) in F1 hybrids and their parents were similar, whereas the maintenance respiration rate (RM) was considerably higher and PN/RM lower in the F1 hybrids than in the parents. Yet at the flowering stage, the hybrids showed higher PN and PN × LAI values, while RM and PN/RM were similar in both. A specific F1 hybrid like IR 62829A×Vajram showed high readings in PN, PN/RM, and PN × LAI at the flowering stage, while IR 62829A×Swarna followed by IR 62829A×Vajram had high values 40 d after planting. The parents Swarna and Vajram, although moderate in PN, had the highest PN × LAI at the flowering stage due to a greater LAI. and M. J. Baig, P. Swain, K. S. Murty.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public