Cadmium (Cd) treatments caused an inhibition in the net photosynthetic rate (PN) of peanut (Arachis hypogaea) plants, due to the reduction of stomatal conductance (gs) and photosynthetic pigment contents, as well as the alteration in leaf structure. The decrease of the transpiration rate and gs might result from the Cd-induced xerophyte anatomic features of leaves (i.e. thick lamina, upper epidermis, palisade mesophyll, high palisade to spongy thickness ratio, as well as abundant and small stomata). The decline of PN was independent of the impairment in photosystem 2. and G. R. Shi, Q. S. Cai.
The study was carried out in a four-year-old super-high density olive grove in Central Italy to compare leaf gas exchanges of Spanish Arbequina and Italian Maurino olive cultivars. Overall, from mid July to mid November, Maurino had a slightly higher maximum
light-saturated net photosynthetic rate (PNmax) than Arbequina. The lowest and the highest PNmax values were recorded at the end of July and in mid November, respectively. Current-season leaves showed similar or slightly higher PNmax values than one-year-old leaves. During the day Maurino always had slightly higher values or values similar to Arbequina, with the highest PNmax being in the morning. Maurino had similar or higher dark respiration rate (RD) values compared to Arbequina. During the day, in both cultivars the RD was lower at 9:00 than in the afternoon. The pattern of the photosynthetic irradiance-response curve was similar in the two genotypes, but the apparent quantum yield (YQ) was higher in Maurino. In both cultivars intercellular CO2 concentration (Ci) tended to increase when PNmax decreased. The increase in Ci corresponded to a decrease in stomatal conductance (gs). The transpiration rate (E) increased from mid July to the beginning of August, then decreased in September and increased again in November. Particularly in the morning, the current-season leaves showed similar or slightly higher E values than the one-year-old leaves. During the day, in both cultivars and at both leaf ages, E was higher in the afternoon. No effects on leaf gas exchanges due to the presence or absence of fruit on the shoot were found. Overall, there was satisfactory physiological adaptation for Arbequina to the conditions of Central Italy and for Maurino to the superintensive grove conditions., P. Proietti, L. Nasini, and L. Ilarioni., and Obsahuje bibliografii
Three-month-old plants of mulberry (Morus alba L. cv. Kanva-2) were subjected to a drought stress by withholding water supply. As the leaf water potential (ΨW) was dropping progressively with the severity of treatment and increasing stress duration, the values of leaf area, dry mass accumulation, total chlorophyll (Chl) content, net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) were declined. The photosystem 2 (PS2) photochemical efficiency significantly decreased only at a severe stress treatment. The intercellular CO2 concentration (Ci) remained unaltered during a mild stress, yet it increased under moderate and severe stresses. The Ci/gs ratio reflected the mesophyll efficiency during water stress. Rewatering of the plants led to an almost complete recovery of PN, E, and gs, indicating that a short-term stress brings about reversible effects only. and S. Ramanjulu ... [et al.].
Unlike mulberry (Morus alba, M.a.), paper mulberry (Broussonetia papyrifera, B.p.) can acclimate to Karst soil and incline to alien invasion. The photosynthetic parameters, diurnal changes of carbonic anhydrase, and chlorophyll fluorescence induction, and water potential were measured on sunny days (SD) and cloudy days (CD). Photosynthetic midday depression occurred in B.p. but not in M.a. The irradiance-and CO2-saturated photosynthetic rates of B.p. were significantly higher than those of M.a. There was no significant difference in water use efficiency between the two species on a SD. The maximum fluorescence, maximum quantum yield, photochemical quenching, and relative electron transport rate in the leaves of B.p. were much higher than those in M.a. The activity of carbonic anhydrase (CA) of B.p., on either an SD or a CD, was much greater than that of M.a. Higher transpiration rate (E) and net photosynthetic rate (PN) of B.p. resulted in the lack of water in mesophyll cells. Although a higher CA activity of B.p. supplied both water and CO2 for the photosynthesis of mesophyll cells, water in mesophyll cells was the factor limiting photosynthesis, and the intercellular CO2 concentration of B.p. was high and stable. and Y.-Y. Wu ... [et al.].
Photosynthetic parameters were studied in Arbutus unedo L. trees growing at either ambient (AC) or elevated EC (mean 465 µmol mol-1) CO2 concentration near a natural CO2 vent in Orciatico, Italy Diurnal courses of net photosynthetic rate (PN), ratio of variable to maximum chlorophyll fluorescence (Fv/Fm), and quantum yield of electron transport through photosystem 2 (Φ2) were measured on sun and shade leaves. The contents of N, C, Ca, K, P, and chlorophyll (Chl) and specific leaf area (SLA) in these leaf categories were also determined. A morning peak and midday depression of PN were found for both AC and EC sun leaves. Long-term EC caused little or no down-acclimation of PN in sum leaves. The estimate of total daily CO2 uptake was lower in AC leaves than in EC leaves. In shade leaves, it reached up to 70 % of the value of sun leaves. The Fv/Fm ratio showed decreasing trend in the morning, reached a minimum at midday (90 % of dawn value), and then increased in the afternoon. The EC had no effect on Fv/Fm either in sun or shade leaves. Plants grown near the CO2 spring had lower Chl content, higher SLA, and higher Ca and K contents than plants grown under AC. and M. Barták, A. Raschi, R. Tognetti.
We compared the photosynthetic traits in response to soil water availability in an endangered plant species Mosla hangchowensis Matsuda and in a weed Mosla dianthera (Buch.-Ham.) Maxim. The highest diurnal mean net photosynthetic rate (PNmean), stomatal conductance (gs), and water use efficiency (WUE) of both species occurred at 60 % soil water holding capacity (WHC), while the lowest values occurred at 20 % WHC. The PNmean, gs, and chlorophyll (Chl) a and b contents of M. hangchowensis were lower than those of M. dianthera, while the physiological plasticity indices were higher than those of M. dianthera. M. hangchowensis had strong adaptability to the changing soil water status but weak extending population ability in its habitats because of the low PNmean, which may be one of the causes of its endangerment. and Y. Ge ... [et al.].
Diurnal variation in net photosynthetic rate (PN) of three-year-old plants of Ginkgo biloba was studied under open, O (receiving full sunlight), net-shade, NS (40 % of photosynthetically active radiation, PAR), or greenhouse, G (25 % PAR) conditions. In all three conditions, PN was higher in morning along with stomatal conductance (gs), and intercellular CO2 concentration (Ci), while leaf temperature and vapour pressure deficit were low. The O-plants exhibited a typical decline in PN during midday, which was not observed in NS-plants. This indicated a possible photoinhibition in O-plants as the ratio of variable to maximum fluorescence (Fv/Fm) and photosystem 2 (PS2) yield (ΦPS2) values were higher in the NS- and G-plants. On the contrary, stomatal density and index, chlorophyll a/b ratio, leaf thickness, and density of mesophyll cells were greater in O-plants. Further, higher PN throughout the day along with higher relative growth rate under NS as compared to O and G suggested the better efficiency of Ginkgo plants under NS conditions. Therefore, this plant species could be grown at 40 % irradiance to meet the ever-increasing demand of leaf and also to increase its export potential. and S. Pandey, S. Kumar, P. K. Nagar.
Independent short-term effects of photosynthetic photon flux density (PPFD) of 50-400 µmol m-2 s-1, external CO2 concentration (C a) of 85-850 cm3 m-3, and vapor pressure deficit (VPD) of 0.9-2.2 kPa on net photosynthetic rate (PN), stomatal conductance (gs), leaf internal CO2 concentration (Ci), and transpiration rates (E) were investigated in three cacao genotypes. In all these genotypes, increasing PPFD from 50 to 400 µmol m-2 s-1 increased PN by about 50 %, but further increases in PPFD up to 1 500 µmol m-2 s-1 had no effect on PN. Increasing Ca significantly increased PN and Ci while gs and E decreased more strongly than in most trees that have been studied. In all genotypes, increasing VPD reduced PN, but the slight decrease in gs and the slight increase in Ci with increasing VPD were non-significant. Increasing VPD significantly increased E and this may have caused the reduction in PN. The unusually small response of gs to VPD could limit the ability of cacao to grow where VPD is high. There were no significant differences in gas exchange characteristics (gs, Ci, E) among the three cacao genotypes under any measurement conditions. and F. C. Baligar ... [et al.].
Response to irradiance of leaf net photosynthetic rates (PN) of four carrot cultivars: Cascade, Caro Choice (CC), Oranza, and Red Core Chantenay (RCC) were examined in a controlled environment. Gas exchange measurements were conducted at photosynthetic active radiation (PAR) from 100 to 1 000 μmol m-2 s-1 at 20 °C and 350 μmol (CO2) mol-1(air). The values of PN were fitted to a rectangular hyperbolic nonlinear regression model. PN for all cultivars increased similarly with increasing PAR but Cascade and Oranza generally had higher PN than CC. None of the cultivars reached saturation at 1 000 μmol m-2 s-1. The predicted PN at saturation
(PNmax) for Cascade, CC, Oranza, and RCC were 19.78, 16.40, 19.79, and 18.11 μmol (CO2) m-2 s-1, respectively. The compensation irradiance (I c) occurred at 54 μmol m-2 s-1 for Cascade, 36 μmol m-2 s-1 for CC, 45 μmol m-2 s-1 for Oranza, and 25 μmol m-2 s-1 for RCC. The quantum yield among the cultivars ranged between 0.057-0.033 mol(CO2) mol-1(PAR) and did not differ. Dark respiration varied from 2.66 μmol m-2 s-1 for Cascade to 0.85 μmol m-2 s-1 for RCC. As PN increased with PAR, intercellular CO2 decreased in a non-linear manner. Increasing PAR increased stomatal conductance and transpiration rate to a peak between 600 and 800 μmol m-2 s-1 followed by a steep decline resulting in sharp increases in water use efficiency. and S. Kyei-Boahen ... [et al.].
We investigated the characteristics of gaseous exchanges and chlorophyll a fluorescence under different irradiances in two liana species Canavalia parviflora Benth. (Fabaceae) and Gouania virgata Reissk (Rhamnaceae), both of a semi-deciduous tropical forest of Southeast Brazil. We used cultivated plants growing under irradiances of 100, 40, 10, and 1.5 % of the photosynthetic photon flux density (PPFD). Higher net photosynthetic rates (PN) were observed during early morning under full sunlight. After this, reduced PN values were recorded due to pronounced stomatal closure. In Canavalia, the gas exchange responses diminished concomitant with reduced irradiance. Gouania exhibited a narrower range of response, with high PN values even at 10 % PPFD. Marked reduction of the effective photochemical yield (ΔF/Fm') near midday was observed, followed by increases in the non-photochemical quenching for both species under full sunlight. Despite the common occurrence of these species in open areas of the forest, both were able to maintain relatively high PN in shaded environments. We suggest that lianas present an intermediate physiological behaviour between shade and non-shade tolerant species. and M. C. Sanches, I. F. M. Válio.