Fusilade (fluazifop-p-butyl) is one of the herbicides that inhibit acetyl-CoA carboxylase. The exogenous effect of 30, 60, and 90 ppm fusilade on peanut (Arachis hypogaea L. cv. Giza 5) leaves was studied. With increasing fusilade concentration, the peanut leaf chlorosis appeared after 7-10 d. Declined leaf pigment contents confirmed the leaf chlorosis. Electron microscopic observation of the fusilade-treated (FT) leaves revealed disorganization in the ultrastructure of mesophyll cell chloroplasts. An increase of plastoglobuli occurrence within chloroplasts and degenerated grana thylakoids were observed in FT leaves. Fusilade treatments induced mainly the enhancement of malondialdehyde content and the activities of peroxidases (guaiacol and ascorbate). On contrary, a decrease in H2O2 content, catalase and superoxide dismutase activities was recorded. Enhancements of the guaiacol and ascorbate peroxidase activities were associated with the decreasing H2O2 content in the FT leaves. Hydrogen peroxide seems not to be involved in the oxidative stress of FT leaves. In the FT leaves, the oxidative stress confirmed by chlorophyll degradation and lipid peroxidation might be caused by the other reactive oxygen species probably due to the decrease of superoxide dismutase activity., K. A. Fayez, D. E. M. Radwan, A. K. Mohamed, A. M. Abdelrahman., and Obsahuje bibliografii
We have examined the effect of gabaculine (3-amino-2,3-dihydrobenzoic acid) on chlorophyll (Chl) binding photosystem (PS) apoproteins in thylakoid ineinbranes relative to the effect on pigment accumulations and grana thylakoid stacking in wheat {Triticum aesíivum L.) seedling leaves. The accumulations of critical PSI, PS2, light- harvesting complex (LHCl and LHC2) apoproteins differed in response to gabaculine treatment. The reaction center proteins. Dl of PS2 and the 68 kDa PSI, were not detected in either primary or secondary leaf chloroplasts of treated etiolated seedlings after greening or secondaiy leaf chloroplasts of treated green seedlings. However, the LHC apoproteins accumulated at reduced levels relative to the Controls and LHCl was more sensitive to treatment than LHC2. Gabaculine decreased plastid pigment levels in primary leaf chloroplasts of treated etiolated seedlings by only 50 % and in secondaiy leaf chloroplasts by more than 85 % of that in the Controls. The accumulations of Chl o, Chl h, and the carotenoids, neoxanthin and í3-carotene, were most sensitive to treatment and were decreased in a similar manner. Granal thylakoid development was more sensitive to treatment than stroma thylakoid development and LHC2 apoprotein accumulations enriched stroma thylakoids in some treatments. The lack of starch and critical reaction center apoproteins in these chloroplasts suggest a loss of photosynthetic competency.
The symbiotic association of endophyte fungus, Neotyphodium lolii, and ryegrass improves the ryegrass resistance to drought. This is shown by a 30 % increase in the number of suckers in infected plants (E+), compared to plants lacking endophyte (E-), and by a higher water potential in the E+ than E- plants. The E+ plants have higher stomatal conductance (gs), transpiration rate, net photosynthetic rate (PN), and photorespiratory electron transport rate than the E- plants. The maximal photochemical efficiency (Fv/Fm) and the actual photochemical efficiency (ΦPS2) are not affected by the endophyte fungus. The increase in PN of the E+ plants subjected to water stress was independent from internal CO2 concentration. An increased PN was observed in E+ plants also in optimal water supply. Hence the drought resistance of E+ plants results in increased gs, PN, and photorespiratory electron transport rate. and C. Amalric ... [et al.].
Spartina maritima (Curtis) Fernald, Spartina densiflora Brong, Arthrocnemum perenne (Miller) Moss, and Arthrocnemum fruticosum (L.) Moq are very frequent halophytes on the coasts of SW Europe. The first two are perennial Gramineae with C4 metabolism; the last two are perennial Chenopodiaceae with C3 metabolism. Controlled garden experiments were carried out with the four species to compare their physiological response, i.e., water potential (Ψ), net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), and chlorophyll fluorescence of photosystem (PS) 2 under saline and non-saline conditions. S. maritima behaves as an osmoconformer species, the other three as osmoregulators. In the four species, PN, E, and gs improved following freshwater irrigation. The variations in PN might be related with biochemical changes (which appear not to affect PS2), but not with significant stomatal fluctuations, which are associated with a lower water use efficiency in the case of Arthrocnemum. The species were segregated into two groups (not depending on their C3 or C4 photosynthetic pathway), in relation with the topographic level of this species in natural conditions: the relative responses of PN in S. maritima and A. perenne were lower than those of S. densiflora and A. fruticosum. The salt-tolerance index supports such segregation. S. densiflora demonstrated the best competitive possibilities against salt-tolerant glycophytes, with its more flexible response in saline or brackish environments, which explains its spreading along the rivers draining into the estuaries of the SW Iberian Peninsula. and F. J. J. Nieva ... [et al.].
The response of gas exchange and chlorophyll fluorescence along with changes in simulated rainfall were studied in water stressed plants Hedysarum fruticosum var. mongolicum (H.f.m.). Net photosynthetic rate (PN), stomatal conductance (gs), leaf water potential (Ψleaf), and apparent carboxylation efficiency (PN/Ci) were significantly increased with the increase of rainfall. However, they did not change synchronously. The complete recovery of both PN and PN/Ci appeared 3 d after watering while gs and Ψleaf were recovered 1 d after treatment. Gas exchange characters increased sharply from 5 to 15 mm rainfall and then maintained steady state with increasing rainfall. During the initial phase of water recovery, photosystem 2 (PS2) activity was not affected and its complete recovery occurred also 3 d after rainfall. Hence the recovery of PN was attributed to both opening of stomata and increase in carboxylation efficiency. Furthermore, PS2 activity was really impaired by water stress and could recover to the normal status when the water stress disappeared. and S. L. Niu ... [et al.].
Seventeen clones of C4 grass Miscanthus spp. collected from different climatic regions and elevations of Taiwan were transplanted in pots. 15-16 months after collection the plants received 0, 1, and 2 g of nitrogen fertiliser (N0, N1, and N2, respectively) per pot. All the measurements were done 10-12 d after N application. The relationships between net photosynthetic rate (PN) and photon flux density (PFD) showed a saturated curve, with PFD saturation at about 1 000 µmol m-2 s-1. The ranges of PFD saturated PN (Psat) for all the tested clones with N0, N1, and N2 were 8-16, 11-18, and 12-21 µmol m-2 s-1, respectively. The clones from southern Taiwan, a tropical region, showed the highest Psat, followed by the clones from northern Taiwan, a subtropical region, while those from mountainous area showed the lowest Psat. The clones collected from southern Taiwan showed the highest frequency of stomata on the adaxial surface, and those collected from the high mountainous area showed the lowest frequency. Also the adaxial surface of leaves from the higher mountainous area had more wax deposited than the leaves from the lowland. Thus the low Psat in mountain clones is limited by both stomatal and non-stomatal factors. Further, the lower leaf conductance and different epidermal characteristics of mountain clones might prevent excessive loss of heat through transpiration and provide production against ultraviolet-B radiation. and J. H. Weng, F. H. Hsu.
Application of 6-benzylaminopurine (BAP) into cultivation medium of potato and tobacco plantlets caused changes in their growth, morphology and photosynthetic parameters in dependence on the plant species and the concentration ušed. The stimulating effect of BAP added to the cultivation medium was found only at very low BAP concentrations (up to 0.01 g m'^ in tobacco and 0.1 g m'^ in potato plantlets). BAP induced only a very slight tendency to increasing chlorophyll (Chl) a+b content and the ratios Chl alb, ChLcarotenoids and net photosynthetic rate/dark respiration rate {P^íIRd) in both plant species. Also the increase of the photochemical efficiency of photosystem 2 as indicated by the ratio of variable to maximal fluorescence (FyT^) and was not statistically significant and was found only in potato plantlets. The stomatal transpiration rate {E^ in tobacco plantlets increased with increasing BAP concentrations up to 0.1 g m'^. However, this was a rather negative effect as it increased a danger of plantlet wilting. In both plant species the BAP concentration of 1.0 g m-^ inhibited growth of plantlet roots; their shoots had altered morphology, their P^, light respiration rate {R\), E^, P^IRy, ratio, Chl contents and parameters of in vivo fluorescence (Fy/Fn,, qp, Rfd) decreased and CO2 compensation concentration increased. This negative effect of BAP was more pronounced in tobacco than in potato plantlets. The above mentioned changes in photosynthetic parameters in plantlets treated with BAP corresponded to the changes in photosynthetic parameters in transgenic plants of the same species with T-DNA carrying gene 4 and resulting from increased level of endogenous cytokinins. However, the application of BAP lead to a decrease in endogenous cytokinins level and thus the effects described are probably due to the action of BAP itself