The basic slow Idnetics and spectral properties of the chlorophyll fluorescence temperature curve (FTC) under low actinic radíation excitation (s 2 W m"2) were measured in primary barley leaves of shade-grown plants. In contrast to the usual Fo temperature dependence, two distinct regions and two maxima of FTC were documented upon a linear heating regime. The fírst maximum situated between 49.5 and 51 °C was less sensitive, whereas Ihe position of the second maximum (between 53 and 63 “C) was strongly dependent on the heating rate. The spectral resolution of the fluorescence emission suggested a presence of photosystem (PS) 1 emission in the FTC at 436 nm excitation and an efíect of partial light-harvesting complex LHCII disconnection from the PS 2 complex at 480 nm excitation. A new fluorescence emission around 700 nm appeared upon heating. The excitation spectra in the 400 nm to 500 nm region for the 685 nm fluorescence emission wavelength indicated that only one emission form was responsible for both of the FTC bands. The 77 K fluorescence spectra at increasing, maximal and decreasing parts of Ihe second FTC band were measured using the triggering expeiiments wilh an incubation temperature of 58 oC. A disconnection of LHCI firom otiier pigment-protein complexes is suggested as a concomitant effect of Ihe second FTC maximum.
The major light-harvesting chlorophyll (Chl) a/b complexes of photosystem II (LHCIIb) play important roles in energy balance of thylakoid membrane. They harvest solar energy, transfer the energy to the reaction center under normal light condition and dissipate excess excitation energy under strong light condition. Many bamboo species could grow very fast even under extremely changing light conditions. In order to explain whether LHCIIb in bamboo contributes to this specific characteristic, the spectroscopic features, the capacity of forming homotrimers and structural stabilities of different isoforms (Lhcb1-3) were investigated. The apoproteins of the three isoforms of LHCIIb in bamboo are overexpressed in vitro and successfully refolded with thylakoid pigments. The sequences of Lhcb1 and Lhcb2 are similar and they are capable of forming homotrimer, while Lhcb3 lacks 10 residues in the N terminus and can not form the homotrimeric structure. The pigment stoichiometries, spectroscopic characteristics, thermo- and photostabilities of different reconstituted Lhcbs reveal that Lhcb3 differs strongly from Lhcb1 and Lhcb2. Lhcb3 possesses the lowest Qy transition energy and the highest thermostability. Lhcb2 is the most stable monomer under strong illumination among all the isoforms. These results suggest that in spite of small differences, different Lhcb isoforms in bamboo possess similar characteristics as those in other higher plants., Z. H. Jiang ... [et al.]., and Obsahuje bibliografii
Osmotic adjustment, accumulation of soluble saccharides, and photosynthetic gas exchange were studied in five durum wheat (Triticum turgidum L. var. durum) and one wild emmer wheat (Triticum turgidum L. var. dicoccoïdes) cultivars of contrasting drought tolerance and yield stability. Soil water contents (SWC) were 100, 31, 20, and 12 % of maximum capillary capacity. Under mild water stress (SWC 31 to 20 %), osmotic adjustment capacity and high accumulation of saccharides were found in cv. Cham1, a high yielding and drought tolerant cultivar, and in var. dicoccoïdes, while lowest values were noted in the durum wheat landraces Oued-Zenati and Jennah-Khotifa. Under more severe water stress (SWC 12 %), the cv. Cham1 maintained higher net photosynthetic rate (PN) than other genotypes. The observed changes in the ratio intercellular/ambient CO2 concentration (ci/ca) indicated that under mild and severe water stress, the decrease in PN was mainly due to stomatal and non-stomatal factors, respectively. and D. Rekika ... [et al.].
Net photosynthetic rate (PN) was studied in field-grown peanut cv. GG 2 in relation to leaf position, time of day, reproductive-sink, and phenophase. In general, PN remained higher in the upper leaves (first from top to the fourth) than in the lower leaves (fifth to eighth). The mean PN of the leaves situated upper and the leaves lower in the canopy increased from the morning, reached a maximum during noon hours, and decreased thereafter. Between 09:00 to 10:00 h, PN, stomatal conductance (gs), and transpiration rate (E) in the upper leaves were higher than in the lower leaves, but between 12:00 and 13:00 h, these activities increased significantly in the lower leaves. Highest PN was found during pod-development phase. Removal of flowers, and hence of active reproductive-sink, decreased plant height and number of leaves, and initiated accumulation of photosynthates in the leaves. The PN per unit leaf area in plants with reproductive-sink (WRS) was similar to those without reproductive-sink (WORS). However, leaf area of WORS plants decreased significantly, mainly due to the reduction in number of leaves. No feed-back inhibition of PN (per unit leaf area) was found despite accumulation of photosynthates in the leaves as a result of removal of the active reproductive-sink. and P. C. Nautiyal, V. Ravindra, Y. C. Joshi.
This paper is aimed at differences in designs of spiral case and impeller of mixed flow pump with regard to suppression of Y-Q characteristic curves instability, pressure pulsations and especially to achieving necessary delivery head. The differences between new and old conception will be explained. The reasons of these differences with regard to flow in pump interior, hydraulic losses, static pressures and velocities will be explained as well.