Morphological, anatomical, and physiological leaf traits of Corylus avellana plants growing in different light conditions within the natural reserve "Siro Negri" (Italy) were analyzed. The results highlighted the capability of C. avellana to grow both in sun and shade conditions throughout several adaptations at leaf level. In particular, the more than 100% higher specific leaf area in shade is associated to a 44% lower palisade to spongy parenchyma thickness ratio compared with that in sun. Moreover, the chlorophyll (Chl) a to Chl b ratio decreased in response to the 97% decrease in photosynthetic photon flux density. The results highlighted the decrease in the ratio of Chl to carotenoid content, the maximum PSII photochemical efficiency, and the actual PSII photochemical efficiency (ΦPSII) associated with the increase in the ratio of photorespiration to net photosynthesis (PN) in sun. Chl a/b ratio was the most significant variable explaining PN variations in shade. In sun, PN was most influenced by the ratio between the fraction of electron transport rate (ETR) used for CO2 assimilation and ETR used for photorespiration, by ΦPSII, nitrogen content per leaf area, and by total Chl content per leaf area. The high phenotypic plasticity of C. avellana (PI = 0.33) shows its responsiveness to light variations. In particular, a greater plasticity of morphological (PIm = 0.41) than of physiological (PIp = 0.36) and anatomical traits (PIa = 0.24) attests to the shade tolerance of the species., R. Catoni, M.U. Granata, F. Sartori, L. Varone, L. Gratani., and Obsahuje bibliografii
Walnut (Juglans regia L.) plantlets were incubated during micropropagation in standard vessels (quasi confmed vessels) or in aerated vessels flushed with 360 or 20 000 cm^(C02) under irradiances of 70 (LI) and 250 (HI) pmol m"^ s'*. Plantlet morphology was strongly affected by the environment; leaf surface was increased, but shoot elongation and number of stems were reduced after increasing the irradiance of culture. Gross photosynthesis (Pq) capacity measured by using the •®02 isotope and mass-spectrometry techniques was increased by increasing photosynthetic photon flux (PPF) and CO2 concentration. Plantlets exhibited a potential for photorespiratory activity and Mehler-type reaction and a high rate of mitochondrial respiration in all vessel types and irradiances. When a long-term HI was applied, gas exchange rates (Pq and O2 uptake) were reduced in most of the vessel and PPF conditions, except in quasi confmed vessels. Under all the growth conditions, net photosynthetic rate (P^) was zero or slightly positive and the dry matter accumulation was very similar. Changes in O2 exchange, growth rate or enzyme activities linked to carbon fixation that were induced by changes in PFD and CO2 concentration showed that the photosynthetic characteristics of plantlets were typical for hetero-mixotrophic tissues.
Photosynthetic assimilatíon of CO2 in a four-year-old plant of lilac, measured in April and in July, was compared. The results were calculated with regard to the surface area of the particular year groups of the stems and to the total surface area of the stems as well as to the globál surface area of the leaves of the plant. In April the stems were the only site of photosynthesis. In July the main organs of CO2 assimilatíon were the leaves, while the participation of the shoots in that period amounted to 2 %. In the process of photosynthesis in the stems mainly the endogenous CO2 was utilized, while the share of exogenous CO2 was 0.02 %. The potential photosynthesis was determined also on the basis of measurements of oxygen release by chloroplasts isolated from the bark and leaves. In July the production of oxygen by chloroplasts ffom the bark of all stems was 5 % of the amount of oxygen released by the chloroplasts isolated from the leaves. In April the production of oxygen by chloroplasts isolated from the bark of the particular year groups of the stems was higher than in July. In the process of CO2 assimilatíon by the bark and leaves the potential Chemical activity of chloroplasts was not fully utilized. The potential CO2 assimilatíon by chloroplasts isolated from the bark was 8.5 times greater than the measured results of CO2 exchange in July and 35.8 times greater in April.
Productivity of most improved major food crops showed stagnation in the past decades. As human population is projected to reach 9-10 billion by the end of the 21st century, agricultural productivity must be increased to ensure their demands. Photosynthetic capacity is the basic process underlying primary biological productivity in green plants and enhancing it might lead to increasing potential of the crop yields. Several approaches may improve the photosynthetic capacity, including integrated systems management, in order to close wide gaps between actual farmer’s and the optimum obtainable yield. Conventional and molecular genetic improvement to increase leaf net photosynthesis (P N) are viable approaches, which have been recently shown in few crops. Bioengineering the more efficient CC4 into C3 system is another ambitious approach that is currently being applied to the C3 rice crop. Two under-researched, yet old important crops native to the tropic Americas (i.e., the CC4 amaranths and the C3-CC4 intermediate cassava), have shown high potential P N, high productivity, high water use efficiency, and tolerance to heat and drought stresses. These physiological traits make them suitable for future agricultural systems, particularly in a globally warming climate. Work on crop canopy photosynthesis included that on flowering genes, which control formation and decline of the canopy photosynthetic activity, have contributed to the climate change research effort. The plant breeders need to select for higher P N to enhance the yield and crop tolerance to environmental stresses. The plant science instructors, and researchers, for various reasons, need to focus more on tropical species and to use the research, highlighted here, as an example of how to increase their yields., M. A. El-Sharkawy., and Obsahuje seznam literatury
Young (12 years old) Norway spruce {Picea abies [L.] Karst.) trees were exposed to ambient CO2 or ambient + 350 |niiol(C02) moL' continuously over 2 growing seasons in open-top chambers, under field conditions of a mountain stand. Comprehesive analysis of CO2 assimílation was performed after 4 and 22 weeks of the second growing season to evaluate the influence of elevated atmospheric CO2. A combination of gas exchange and a mathematical model of ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBPCO) activity was ušed. After 4 weeks of exposure no statistically significant stimulation of the radiant energy and CO2 saturated rate of CO2 uptake (ENsat) by the elevated CO2 concentration was found. Yet after 24 weeks a statistically significant depression of Ejvjsa, (38 %) and carboxylation efficiency (32 %) was observed. Depression of photosynthetic activity by elevated CO2 resulted from a decrease in the RuBPCO carboxylation rate. The electron transport rate was also modified similarly to the rate of RuBP formation. An accompanying decrease in nitrogen content of the needles (by 12 %) together with an increase in total saccharides (by 34 %) was observed after 24 weeks of exposure to enhanced CO2.
To investigate how bisulfite promotes photosynthesis, a pot experiment was conducted with rice (Oryza sativa L.) plants to determine Rubisco activity and content, and Rubisco activase (RCA) gene expression after spraying NaHSO3 on rice leaves. The NaHSO3 treatment promoted significantly net photosynthetic rate (PN), carboxylation efficiency, maximum carboxylation rate, ribulose-1,5-bisphosphate regeneration rate, initial Rubisco activity, and RCA protein and mRNA concentrations. Therefore, the NaHSO3 enhancement of PN could be directly attributed to induction of RCA gene expression both at the transcription and translation levels. Thus, the increased RCA regulated the initial Rubisco activity in vivo., Y. Chen, J.-H. Jin, Q.-S. Jiang, C.-L. Yu, J. Chen, L.-G Xu, D.-A. Jiang., and Obsahuje bibliografii
Young leaves of tropical trees frequently appear red in color, with the redness disappearing as the leaves mature. During leaf expansion, plants may employ photoprotective mechanisms to cope with high light intensities; however, the variations in anthocyanin contents, nonphotochemical quenching (NPQ), and photorespiration during leaf expansion are poorly understood. Here, we investigated pigment contents, gas exchange, and chlorophyll (Chl) fluorescence in Woodfordia fruticosa leaves during their expansion. Young red leaves had significantly lower Chl content than that of expanding or mature leaves, but they accumulated significantly higher anthocyanins and dissipated more excited light energy through NPQ. As the leaves matured, net photosynthetic rate, total electron flow through PSII, and electron flow for
ribulose-1,5-bisphosphate oxygenation gradually increased. Our results provided evidence that photorespiration is of fundamental importance in regulating the photosynthetic electron flow and CO2 assimilation during leaf expansion., S.-B. Zhang, J.-L. Zhang., and Obsahuje seznam literatury