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1174. Gas exchange and chlorophyll fluorescence in symbiotic and non-symbiotic ryegrass under water stress

Creator:
Amalric, C., Sallanon, H., Monnet, F., Hitmi, A., and Coudret, A.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
endophyte, Lolium perenne, Neotyphodium lolii, photosynthesis, stomatal conductance, transpiration rate, and water potential
Language:
Multiple languages
Description:
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.].
Rights:
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1175. Gas exchange and chlorophyll fluorescence of C3 and C4 saltmarsh species

Creator:
Nieva, F. J. J., Castellanos, E. M., Figueroa, M. E., and Gil, F.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Arthrocnemum, C3 and C4 plants, halophytes, intercellular CO2 concentration, leaf gas exchange, net photosynthetic rate, Spartina, stomatal conductance, transpiration rate, and water potential
Language:
Multiple languages
Description:
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.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1176. Gas exchange and chlorophyll fluorescence response to simulated rainfall in Hedysarum fruticosum var. mongolicum

Creator:
Niu, S. L., Li, L. H., Jiang, G. M., Gao, L. M., Li, Y. G., Peng, Y., and Liu, M. Z.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
apparent carboxylation efficiency, gas exchange, leaf water potential, net photosynthetic rate, soil water content, and stomatal conductance
Language:
Multiple languages
Description:
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.].
Rights:
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1177. Gas exchange and epidermal characteristics of Miscanthus populations in Taiwan varying with habitats and nitrogen application

Creator:
Weng, J.-H. and Hsu, F.-H.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
adaxial and abaxial leaf surfaces, altitude, C4 plant, clone differences, ecotypes, leaf conductance, mesophyll conductance, photosynthesis, and stomatal frequency
Language:
Multiple languages
Description:
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.
Rights:
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1178. Gas exchange and in vivo chlorophyll fluorescence in potato and tobacco plantlets in vitro as affected by various concentrations of 6-benzylaniinopurine

Creator:
Pospíšilová, J., Čatský, J., Macháčková, I., and Solárová, J.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
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
Rights:
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1179. Gas exchange and leaf water status in potted plants of Copaifera langsdorffii. 1. Responses to water stress

Creator:
Prado, C.H.B.A., de Moraes, J.A.P.V., and de Mattos, E.A.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
Gas exchange and leaf water potential were investigated with regard to water stress in potted 6-month old plants of Copaifera langsdorffii. Leaf water potential (Ψ = -2.0 MPa) in stressed plants was near the osmotic potential (π = -2.2 MPa) at 0900 h during 22 d with water stress. Transpiration rates (if were in linear relation to stomatal conductance (gs) during stress, while water potential and net photosynthetic rate (PN) at 0900 h were in a curvilinear relation. More pronounced decrease of P N occurred only at gs between 0.01 to 0.08 mol nr2 s-1. Increase in water use efficiency (WUE) coincided with morning Ψ diminution from -2.0 MPa to -2.2 MPa. This 10 % decrease in Ψ corresponded to a 60 % decrease in gs (from 0.15 to 0.06 mol m*2 s*1). When pre-dawn Ψ (-3.4 MPa) was close to the Ψ measured at 0900 h (-3.5 MPa), both the and gs were around zero. Therefore, Ψ at 0900 h, π and values of gas exchange were closely related during the days of stress. Values of Ψ for zero and for stomatal closure (-3.5 MPa) were in the same range for sclerophyllous plants.
Rights:
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1180. Gas exchange and leaf water status in potted plants of Copaifera langsdorffii. 2. Probable influence of low air humidity

Creator:
Prado, C.H.B.A., de Moraes, J.A.P.V., and de Mattos, E.A.
Format:
print
Type:
model:internalpart and TEXT
Subject:
daily courses of gas exchange, leaf-air water vapour concentration difference, leaf water potential, net photosynthetic rate, soil moisture, stomatal conductance, and water use efficiency
Language:
Multiple languages
Description:
The influence of air humidity on leaf-air gas exchange and leaf water potential (4^) was investigated during daily courses in control and water stressed potted young plants of Copaifera langsdorffii. When leaf-air water vapour concentration difference (AW) increased during the day, stomatal conductance (g^) and net photosynthetic rate (P]vj) decreased under both soil moistures. Moderate AW induced lower values of g^ and Pn unwatered than control plants, High AW in atmosphere produced strong depression in g^ (from 0.22 to 0,01 mol m'^ s’’) and (from 6.5 to 0.7 pmol m'2 s'*) in control plants around midday, with recuperation of T'. Expected conductance tese) was calculated as fimction of AW, which was useful for discriminating soil to atmosphere water stress. In špite of momentary T or soil water stress, P^, g^, and water use efficiency decreased when AW increased during day course.
Rights:
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