Influence of supra-optimal concentrations of K on growth, water relations, and photosynthetic capacity in pearl millet under severe water deficit conditions was assessed in a glasshouse. Nineteen-days-old plants of two lines, ICMV-94133 and WCA-78, of Pennisetum glaucum (L.) R.Br. were subjected for 30 d to 235.0, 352.5, and 470.0 mg(K) kg-1(soil) and two water regimes (100 and 30 % field capacity). Increasing K supply did not alleviate the effect of water deficit on the growth of two lines of pearl millet since additional amount of K in the growth medium had no effect on shoot dry mass, relative growth rate, plant leaf area, net assimilation rate, or leaf area ratio, although there was significant effect of drought stress on these variables. Soil moisture had a significant effect on net photosynthetic rate (PN), transpiration rate, stomatal conductance, and water use efficiency of both pearl millet lines, but there was no significant effect of varying K supply on these variables. In WCA-78 an ameliorative effect of increasing supply of K on PN was observed under water deficit. Chlorophyll (Chl) a and b contents increased significantly in both lines with increase in K supply under well watered conditions, but under water deficit they increased only in ICMV-94133. Chl a/b ratios were reduced significantly in WCA-78 with increasing K supply under both watering regimes, but by contrast, in ICMV-94133 this variable was decreased only under water stress. Leaf water potential and osmotic potential of both lines decreased significantly with the imposition of drought. Leaf pressure potential in both lines increased with increase in K supply under water stress. Contents of total free amino acids in the leaves of both pearl millet lines increased significantly with increase in K supply under water stress. Potassium supply had no effect on leaf soluble sugars or soluble proteins. Considerable osmotic adjustment occurred in pearl millet plants experiencing water deficit under high K supply. and M. Ashraf, Ashfaq Ahmad, T. McNeilly.
Seedlings of Bidens cernua L. emerged when mean air temperature was 17.0±1.3 °C. The highest net photosynthetic rate (PN), 13.8±0.8 µmol(CO2) m-2 s-1, was monitored during the vegetative period (May-August), decreasing on an average by 50 % during flowering (August-September) and during fruiting (September-November) phases. The senescence phase (October-November) was characterised by 79, 58, and 18 % decrease of PN, chlorophyll content, and leaf area (LA), respectively, from the maximum values. The time span from seedling emergence to the end of fruiting phase was 202 d. The total plant biomass was 1.58±0.05 g of which 81 % was aboveground plant portion. The total dry mass relative growth rate averaged over the assimilation period was 0.0804±0.0002 kg kg-1 d-1, and it was correlated to both the net assimilation rate (NAR) and the leaf area ratio (LAR). and L. Gratani ... [et al.].
The effect of elevated carbon dioxide (600±50 cm3 m-3; C600) on growth performance, biomass production, and photosynthesis of Cenchrus ciliaris L. cv. 3108 was studied. This crop responded significantly by plant height, leaf length and width, and biomass production under C600. Leaf area index increased triple fold in the crops grown in the open top chamber with C600. The biomass production in term of fresh and dry biomass accumulation increased by 134.35 (fresh) and 193.34 (dry) % over the control (C360) condition where the crops were grown for 20 d. The rate of photosynthesis and stomatal conductance increased by 24.51 and 46.33 %, respectively, in C600 over C360 plants. In comparison with C360, the rate of transpiration decreased by 6.8 % under C600. Long-term exposure (120 d) to C600 enhanced photosynthetic water use efficiency by 34 %. Also the contents of chlorophylls a and b significantly increased in C600. Thus C. ciliaris grown in C600 throughout the crop season may produce more fodder in terms of green biomass. and R. K. Bhatt, M. J. Baig, H. S. Tiwari.
Comparative analysis revealed that a xantha rice mutant (cv. Huangyu B) had higher ratios of chlorophyll (Chl) a/b and carotenoids/Chl, and higher photosynthetic efficiency than its wild type parent (cv. II32 B). Unexpectedly, the mutant had higher net photosynthetic rate (PN) than II32 B. This might have resulted from its lower non-photochemical quenching (qN) but higher maximal photochemical efficiency (FV/FM), higher excitation energy capture efficiency of photosystem 2 (PS2) reaction centres (FV'/FM'), higher photochemical quenching (qP), higher effective PS2 quantum yield (ΦPS2), and higher non-cyclic electron transport rate (ETR). This is the first report of a chlorophyll mutant that has higher photosynthetic efficiency and main Chl fluorescence parameters than its wild type. This mutant could become a unique material both for the basic research on photosynthesis and for the development of high yielding rice cultivars. and X.-S. Zhou ... [et al.].
The study of leaf vascular systems is important in order to understand the fluid dynamics of water movement in leaves. Recent studies have shown how these systems can be involved in the performance of photosynthesis, which is linked to the density of the vascular network per unit of leaf area. The aim of the present study was to highlight the correlation between a leaf vein density (VD) and net photosynthetic rate (PN), which was undertaken using a digital camera, a stereoscopic microscope, and a light source. The proposed hypothesis was tested, for the first time, on the leaves of two cultivars of Vitis vinifera (L.). A significant difference was found between the VD of mature leaves of the two cultivars. VD was also significantly correlated with the maximum leaf PN. These findings support the hypothesis that the vascular system of grape leaves can be correlated with leaf photosynthesis performance., M. Pagano, P. Corona, P. Storchi., and Obsahuje bibliografii
The aim of the current work was to determine whether grafting could improve salinity tolerance of melon and cucumber, and whether possible induction of tolerance to salt stress was associated with the protection of the photosynthetic apparatus. Two greenhouse experiments were carried out to determine gas exchange, mineral composition, growth and yield of melon (Cucumis melo L. cv. Cyrano) and cucumber (Cucumis sativus L. cv. Akito) plants, either ungrafted or grafted onto the Cucurbita hybrid rootstocks (Cucurbita maxima Duch. × Cucurbita moschata Duch.), ‘P360’, and ‘PS1313’, respectively. Plants were grown hydroponically and supplied with two nutrient solutions - a nonsalinized control and a salinized solution which contained 40 mmol L-1 of NaCl. Salinity induced a smaller decrease in leaf area index (LAI), in grafted-compared to ungrafted plants. Similarly, the
PN and gs reduction in NaCl treatment compared to control were significantly lower in grafted plants (34% and 34%, respectively, for melon and 14% and 15.5%, respectively, for cucumber) compared to ungrafted plants (42% and 40%, respectively, for melon and 30% and 21%, respectively, for cucumber). In all grafting combinations, negative correlations were recorded between Na+ and Cl- in the leaf tissue and PN. Grafting reduced concentrations of sodium, but not chloride, in leaves. Under saline conditions a smaller reduction in melon and cucumber shoot biomass dry mass and fruit yield were recorded, with positive correlations between shoot biomass, yield and PN. These results suggest that the use of salt tolerant Cucurbita rootstock can improve melon and cucumber photosynthetic capacity under salt stress and consequently crop performance., Y. Rouphael ... [et al.]., and Obsahuje bibliografii
Excess solar radiation under hot climate can lead to decline in photosynthetic activity with detrimental effects on growth and yield. The aim of this study was to evaluate the use of a transparent plastic roof as shading for diurnal changes in photosynthetic gas exchange, chlorophyll fluorescence, fruit set and quality of mango (Mangifera indica L.) cv. 'Nam Dok Mai' growth in the field conditions. Fully expanded leaves were examined either shaded by the plastic roof or sunlit under natural conditions. Leaf temperature and leaf-to-air vapour pressure deficit of the shaded leaves measured on the clear day were lowered compared to those of the sunlit leaves. It resulted in increased stomatal conductance and photosynthetic rates of the shaded leaves compared to those of the sunlit leaves, especially from the morning to midday. Furthermore, the reversible decrease of the maximal quantum yield of PSII was more pronounced in the sunlit leaves than that in the shaded ones. Shading increased the total fruit number; the shaded fruits developed better external color than that of the sun-exposed fruits. Our results indicated that shading could maintain the high photosynthetic activity by reducing stomatal limitations for carbon supply and was effective in alleviating the photoinhibitory damage to PSII during bright and clear days with excessive radiation. Finally, shading could increase the number of fruits and improve mango peel color., K. Jutamanee, S. Onnom., and Obsahuje bibliografii
We tested the usefulness of chlorophyll a fluorescence quenching analysis for the selection of maize parental inbred lines able to produce F1 hybrids with a high CO2 assimilation rate during growth at suboptimal temperature. Fifty inbred lines, grown at 15 °C, showed at 6 °C a broad genetic variability regarding the quantum yield of photosynthetic electron transport (ΦPS2). A decrease of ΦPS2 in sensitive lines was caused more by reduction of the efficiency of excitation energy capture by open photosystem 2 (PS2) reaction centres (Fv'/Fm') than by a drop in photochemical quenching (qP). Selected inbred lines with the highest (H) and the lowest (L) values of ΦPS2 were used for separate crossings in a diallelic arrangement. Twenty-one of H×H hybrids and 21 of the L×L hybrids were grown at 15 °C. The H×H hybrids showed at suboptimal temperature a significantly higher transport of photosynthetic electrons than the L×L hybrids at lower (400) as well as at higher [800 μmol(photon) m-2 s-1] irradiance. The mean net photosynthetic rate (PN) in H×H and L×L hybrids amounted to 8.4 and 5.8 (second leaf) and 8.5 and 7.6 μmol(CO2) m-2 s-1 (third leaf), respectively. Among the best 20 hybrids with regard to PN (values larger than the average) of second leaves, as many as 15 were derived from H lines (75 % of hybrids), whereas among the best 21 hybrids with regard to PN of the third leaves, 16 were derived from H lines (76 % of hybrids). The intensive PN of H×H hybrids was most often accompanied by less water lost via transpiration in relation to photosynthesis than in the hybrids of L lines. Hence an analysis of chlorophyll a fluorescence quenching enables the selection of inbred lines, which can produce hybrids with improved CO2 fixation and with efficient water management during growth at suboptimal temperature. and J. Kościelniak, F. Janowiak, Z. Kurczych.
Anthropogenic activities are changing global precipitation regimes and result in many middle latitude arid and semiarid regions experiencing less precipitation and more extreme weather events. However, little is known about the response of active ingredient accumulation in the medicinal herb Plantago depressa Willd. Therefore, we carried out a greenhouse experiment in order to study effect of control (CK, normal water supply equal to 309 mm per four months), -30 (-WS) and +30% (+WS) of the control water supply on the photosynthesis (PN), C/N ratio, and plantamajoside accumulation in P. depressa. Our results showed that compared with the-WS and CK treatments, the +WS treatment significantly enhanced biomass, the C/N ratio, plantamajoside concentration, yield in shoots and roots, and PN, but declined the N concentration in shoots and roots. The plantamajoside concentration was positively correlated with PN, the soluble sugar content, and the C/N ratio, but negatively correlated with the N concentration. Our results suggested that, under experimental conditions, +WS increased the C/N ratio and promoted the plantamajoside accumulation of P. depressa., Z. Li, W. Bai, L. Zhang, L. Li., and Obsahuje bibliografii
Insect-infested (II) acorns germinated 3 d earlier than the healthy (H) ones. However, germination ratio of II-acorns was strongly decreased compared with H-acorns and there were great differences in activities of amylase. We found an apparently lower net photosynthetic rate and total chlorophyll contents of the first true leaf of II-acorns than of the H-ones. Maximal photochemical efficiency of photosystem 2 (PS2, Fv/Fm) decreased in seedlings germinated from II-acorns than from the H-ones. Infestation of insects, especially for weevil (Curculio spp.) had significantly negative effects on length of taproots, height of plants, dry mass (DM) of roots and the first fully expanded true leaf. Leaf area and total N content of the first true leaf declined due to limitation of resource reserves in cotyledons. Damage of cotyledons caused by weevil accounted much for poor development of seedlings germinated from II-acorns. A mutual relationship between seedling establishment and seed-infesting insects may exist due to high predation on H-acorns by small rodents. and X. F. Yi, Z. B. Zhang