F0 fluorescence and thermoluminescence (TL) were recorded simultaneously on various dark-adapted leaf samples. Above 40 °C, a sharp peak of TL coincided with the onset of the heat-induced F0 rise. It results from a back-transfer of an electron from the secondary QB- to the primary acceptor QA of photosystem 2, followed by a luminescence-emitting recombination with Tyr-D1. This demonstrates that the critical temperature at which the F0 starts rising also corresponds to a shift towards the left of the QA↔QB- equilibrium.
Effects of Quercus ilex acorn size on seedling morphological and physiological traits were analysed. The study was carried out with five populations from different geographical areas and covering an aridity gradient. Seedling morphological traits (height and total leaf area) were analyzed during the first growing year. Physiological traits (net photosynthesis, stomatal conductance, leaf transpiration, and intrinsic water-use efficiency) were analysed at different air temperatures during spring, summer, and winter months, and in response to water stress. There were significant correlations among the considered acorn (volume, fresh mass) and seedling traits. Differences in growth and physiological traits among the considered populations were found. The larger differences in the growth parameters were observed during the first growing season, and they could be justified by the significant differences among acorn size. On the contrary, the physiological response to air temperature and aridity was more related to the geographical origin of the considered populations than to acorn size. Q. ilex acorn and seedling traits more tolerant to drought might have a high potential for vegetation recovery in afforestation projects and restoration programmes particularly under water-limited environments or in degraded areas. and A. Bonito ... [et al.].
14CO2 uptake in leaves of wheat plants (Triticum aestivum L.) fertilized by urea or Ca(NO3)2 (25 mol m-3) was investigated. The Warburg effect (inhibition of 14CO2 uptake by oxygen) under 0.03 vol. % CO2 concentration was observed only in non-fertilized plants. Under 0.03 vol. % CO2, the Warburg antieffect (stimulation of 14CO2 uptake by oxygen) was detected only in plants fertilized by Ca(NO3)2. Under saturating CO2 concentration (0.30 vol. %), the Warburg antieffect was observed in all variants. Under limitation of ribulose-1,5-bisphosphate carboxylase/oxygenase activity (0.30 vol. % CO2 + 1 vol. % O2), the rate of synthesis of glycollate metabolism products decreased in control and urea-fertilized plants but was enhanced in nitrate-fed plants. Hence, there was an activation of glycollate formation via transketolase reaction in fertilized plants, and the products of nitrate reduction function were oxidants in nitrate-fertilized plants whereas the superoxide radical played this role in urea-fertilized plants. and V. Chikov, G. Bakirova.
In a field experiment the chlorophyll (a+b) (SPAD readings) and nitrogen contents of three grass species (Festuca arundinacea Schreb., Lolium perenne L., and Lolium multiflorum Lam.) and three intergeneric hybrids of Festuca pratensis Huds. × Lolium multiflorum Lam. and Festuca arundinacea Schreb. × Lolium multiflorum Lam. were measured. Close relationships were found between SPAD readings and nitrogen leaf content (r2 = 0.873** 0.491** and 0.938**) for the 1st, 2nd, and 3rd cut, respectively. SPAD readings and N contents were closely correlated (r = 0.836**) confirming that SPAD measurements could be used in grass selection and/or breeding for high N concentration in herbage.
Flavonoids are thought to participate in protection of the photosynthetic apparatus against photoinhibition under excessive light. Flavone glycoside, scutellarin, is a main active ingredient extracted from Erigeron breviscapus, the plant used in Chinese medicine. Shade-developed leaves of E. breviscapus were transferred from shade to full sunlight to quantify a relationship between the concentration of leaf scutellarin and tolerance to high radiation stress or the recovery from photoinhibition. The maximal quantum yield of PSII photochemistry showed a diurnal fluctuation in both shaded and sunlit leaves throughout the day. It indicated dynamic photoinhibition in the leaves of Erigeron, i.e., higher photoinhibition at solar noon and lower one in the morning and late afternoon. The sun-developed leaves reached the higher scutellarin content and values of nonphotochemical quenching coefficient with a lower degree of photoinhibition than the shade-developed leaves. When the shade-developed leaves were transferred to full sunlight, the content of scutellarin was declining continuously for 10 d and then was increasing for 15 d. After 50 d, all leaves became the sun-developed leaves with their scutellarin contents of about 138.5 ± 5.2 mg g-1(dry mass, DM) which was significantly higher than that of the shade-developed leaves [107.8 ± 9.8 mg g-1(DM)]. During acclimatization, the degree of photoinhibition was negatively correlated with the scutellarin content. Our results demonstrated a synchronous fluctuation between the flavonoid content and degree of protection against photoinhibition., R. Zhou, W. H. Su, G. F. Zhang, Y. N. Zhang, X. R. Guo., and Obsahuje seznam literatury
Leaf protein content and net photosynthetíc rate (P^) were estimated at monthly intervals in seven tropical deciduous tree species, námely Chukrasia tabularis, Dolichandrone atrovirens, Eugenia Jambolana, Gmelina arborea, Lannea coromandelica, Terminalia arjuna and Terminalia bellerica firom September 1990 to August 1991. Among the seven tree species examined, Terminalia arjuna exhibited a significant positive correlation (r = 0.81; p < 0.05) between leaf protein content and while in others it was found insignificant.
The relationship between net photosynthetic (PN) and leaf respiration (R) rates of Quercus ilex, Phillyrea latifolia, Myrtus communis, Arbutus unedo, and Cistus incanus was monitored in the period February 2006 to February 2007. The species investigated had low R and PN during winter, increasing from March to May, when mean air temperature reached 19.2 °C. During the favourable period, C. incanus and A. unedo had a higher mean PN (16.4±2.4 µmol m-2 s-1) than P. latifolia, Q. ilex, and M. communis (10.0±1.3 µmol m-2 s-1). The highest R (1.89±0.30 µmol m-2 s-1, mean of the species), associated to a significant PN decrease (62 % of the maximum, mean value of the species), was measured in July (mean R/PN ratio 0.447±0.091). Q10, indicating the respiration sensitivity to short-term temperature increase, was in the range 1.49 to 2.21. Global change might modify R/PN determining differences in dry matter accumulation among the species, and Q. ilex and P. latifolia might be the most favoured species by their ability to maintain sufficiently higher PN and lower R during stress periods. and L. Gratani, L. Varone, R. Catoni.
Field studies with segregating populations under short days showed a significant positive correlation between tuber yield and the light-saturated net photosynthetic rate (Fn) in the 4th leaf from the top, at the tuber formation stage, in two seasons. The leaf area per plant {A) at this stage and also at the tuber bulking stage had a significant positive correlation with tuber yield. The product of PN and A also showed a significant positive correlation with tuber yield at both of these stages, a stronger one than that between tuber yield and A at the tuber formation stage.