Gas Exchange Characteristics of the Flue-Cured Tobacco (Nicotiana Tabacum L.) Cultivars Grown under Two Production Systems

The net photosynthetic rate (P _N), intercellular CO₂ concentration (C _i), stomatal conductance (g _s), transpiration rate (E), water use efficiency (WUE), and leaf biomass production of four American flue-cured tobacco (Nicotiana tabacum L.) cultivars K 326, K 358, and Speight G 28 were compared with three local Indian cultivars 16/103, Special FCV, and PCT-7, during 1994 and 1995 crop seasons under irrigated and rainfed production systems (Northern light soils, NLS, and Karnataka light soils, KLS) in India. By comparison, the American tobacco cv. K 326 showed the highest P _N and g _s. A positive correlation was found between P _N and biomass production in all the varieties tested (r = 0.55 in NLS and 0.73 in KLS). The American cultivars were superior than the local cultivars in their biomass production and P _N under Indian farming conditions.     

Photosynthesis Parameters in Two Cultivars of Mulberry Differing in Salt Tolerance

Three-month-old mulberry (Morus alba L.) cultivars (salt tolerant cv. S1 and salt sensitive cv. ATP) were subjected to different concentrations of NaCl for 12 d. Leaf area, dry mass accumulation, total chlorophyll (Chl) content, net CO₂ assimilation rate (P _N), stomatal conductance (g _s), and transpiration rate (E) declined, and intercellular CO₂ concentration (C _i) increased. The changes in these parameters were dependent on stress severity and duration, and differed between the two cultivars. The tolerant cultivar showed a lesser reduction in P _N and g _s coupled with a better C _i and water use efficiency (WUE) than the sensitive cultivar. This revised version was published online in June 2006 with corrections to the Cover Date.     

Diurnal and Seasonal Changes in Photosynthetic Characteristics in Different Olive (Olea europaea L.) Cultivars

Diurnal and seasonal changes in photosynthetic characteristics, leaf area dry mass (ADM), and reducing sugar and total chlorophyll (Chl) contents of leaves of Frantoio, Leccino, and Maurino olive cultivars were investigated in Central Italy. Leaf net photosynthetic rate (P _N) per unit leaf area changed during the growing season and during the day, but the cultivar did not significantly influence the changes. In both young and one-year-old leaves the highest P _N values were observed in October, while the lowest values were recorded in August and December; during the day the highest P _N values were generally found in the morning. The pattern of photosynthetic response to photosynthetic photon flux density (PPFD) of leaves was similar in the three genotypes. Sub-stomatal CO₂ concentration (C _I) tended to increase when P _N decreased. The increase in C _I was accompanied by a stomatal conductance to water vapor (g _S) decrease. In general, P _N and dark respiration rate (R _D) were correlated. Transpiration rate (E), with no differences between the cultivars, increased from April to July, decreased greatly in August, then increased in October and finally decreased again in December. Leaf water content increased from April to June, remained high until mid July, decreased significantly in August, remaining constant until December with no differences associated with the cultivar. In both young and one-year-old leaves, the leaf water content per unit leaf area was slightly greater in Frantoio than in the other two cultivars. The one-year-old leaves had a higher Chl content than the young ones. The cultivar did not substantially influence the leaf reducing sugar content which decreased from April to August, when it reached the lowest level, then increased rapidly until October. During the day the reducing sugar content did not change significantly. The leaf ADM was slightly higher in Frantoio than in the other cultivars and one-year-old leaves had higher values than the young ones. Leaf ADM decreased from April to June and then tended to increase until December. During the day there were no substantial variations.     

The Effect of Abscisic Acid and Methyl Jasmonate on Carbonic Anhydrase Activity in Pea

Short-term (2 h) treatment with 10 μM abscisic acid decreased stomatal conductance and net photosynthetic rate, and increased carbonic anhydrase activity in pea seedlings. The treatment with 10 μM methyl jasmonate did not significantly affect these parameters. This revised version was published online in June 2006 with corrections to the Cover Date.     

Photosynthetic characteristics of <Emphasis Type="Italic">Hordeum,Triticum, Rumex</Emphasis>, and <Emphasis Type="Italic">Trifolium</Emphasis> species at contrasting altitudes

Photosynthetic characteristics were compared between plants of low altitude (LA) grown at LA (Palampur; 1 300 m) and at high altitude, HA (Kibber; 4 200 m), and plants naturally occurring at different altitudes (Palampur, 1 300 m; Palchan, 2 250 m; and Marhi, 3 250 m). Net photosynthetic rate (P _N) was not significantly different between altitudes. However, the slopes of the curve relating P _N to intercellular CO₂ concentration (C _i) were higher in plants at Palchan, Marhi, and Kibber compared to those at Palampur, indicating that plants had higher efficiency of carbon uptake (the initial slope of P _N/C _i curve is an indication) at HA. They had also higher stomatal conductance (g _s), transpiration rate, and lower water use efficiency at HA. g _s was insensitive to photosynthetic photon flux density (PPFD) for plants naturally occurring at Palampur, Palchan, and Marhi, whereas plants from LA grown at Palampur and Kibber responded linearly to increasing PPFD. Insensitivity of g _s to PPFD could be one of the adaptive features allowing wider altitudinal distribution of the plants.This research is supported by the Department of Biotechnology (DBT), Government of India vide grant number BT/PR/502/AGR/08/39/966-VI.     

Responses of Two Olive Tree (Olea Europaea L.) Cultivars to Elevated CO2 Concentration in the Field

Five-year-old plants of two olive cultivars (Frantoio and Moraiolo) grown in large pots were exposed for 7 to 8 months to ambient (AC) or elevated (EC) CO₂ concentration in a free-air CO₂ enrichment (FACE) facility. Exposure to EC enhanced net photosynthetic rate (P _N) and decreased stomatal conductance, leading to greater instantaneous transpiration efficiency. Stomata density also decreased under EC, while the ratio of intercellular (C _i) to atmospheric CO₂ concentration and chlorophyll content did not differ, except for the cv. Moraiolo after seven months of exposure to EC. Analysis of the relationship between photosynthesis and C _i indicated no significant change in carboxylation efficiency of ribulose-1,5-bisphosphate carboxylase/oxygenase after five months of exposure to EC. Based on estimates derived from the P _N-C _i relationship, there were no apparent treatment differences in daytime respiration, CO₂ compensation concentration, CO₂-saturated photosynthetic rate, or photosynthetic rate at the mean C _i, but there was a reduction in stomata limitation to P _N at EC. Thus 5-year-old olive trees did not exhibit down regulation of leaf-level photosynthesis in their response to EC, though some indication of adjustment was evident for the cv. Frantoio with respect to the cv. Moraiolo.     

Genotype Variability in Photosynthetic Characteristics in Finger Millet

High variability in leaf gas exchange and related traits were found in 30 genotypes of field grown finger millet. The variability in carbon exchange rate per unit leaf area (P _N) can be partly attributed to the differences in the stomatal conductance (g_s) and area leaf mass (ALM). The P _N was positively correlated with total dry matter (TDM). However, no relationship between P _N and seed yield was found. The leaf area showed a positive and significant correlation with total biomass. None of the other gas-exchange traits had significant relationship either with TDM or with seed yield. The ALM showed a strong positive association with P _N. However, it was not correlated with either total biomass or seed yield. As a result, the use of ALM as surrogate for P _N for identifying high biomass producing genotypes only had a limited value. Hence selection for high P _N would result in higher biomass producing types.     

A Comparison of Photosynthetic Capacity between Myrica Gale var. Tomentosa a Nitrogen-Fixing Shrub,and Co-Occurring Species in an Oligotrophic Moor

Photosynthetic and transpiration (E) rates, stomatal conductance, and leaf nitrogen content were surveyed for Myrica gale var. tomentosa, a N₂-fixing wetland shrub, Betula platyphylla var. japonica, and Rhododendron japonicum in Ozegahara moor, an oligotrophic moor in Central Japan. Net photosynthetic rate saturated with irradiance (P_max) of M. gale was 15.2-16.5 μmol(CO₂) m^-2 s^-1, higher than those of the other species throughout the growing season. P_max was positively correlated with leaf N content among the three species. The large leaf N content in M. gale was due to N₂-fixation in root nodules. In a comparison of M. gale in two habitats, P_max, leaf N content, and root nodule development were larger in the wetter habitat. M. gale showed high E and no midday depression of P_max even under high irradiance and large vapour pressure deficit between leaves and ambient air on a midsummer day. These traits of photosynthesis and water relations were associated with the dominance of this shrub in wetter sites such as stream sides and hollows. This revised version was published online in September 2006 with corrections to the Cover Date.     

Photosynthetic responses of apricot (<Emphasis Type="Italic">Prunus armeniaca</Emphasis> L.) to photosynthetic photon flux density,leaf temperature,and CO<Subscript>2</Subscript> concentration

Two cultivars (Katy and Erhuacao) of apricot (Prunus armeniaca L.) were evaluated under open-field and solar-heated greenhouse conditions in northwest China, to determine the effect of photosynthetic photon flux density (PPFD), leaf temperature, and CO₂ concentration on the net photosynthetic rate (P _N). In greenhouse, Katy registered 28.3 μmol m⁻² s⁻¹ for compensation irradiance and 823 μmol m⁻² s⁻¹ for saturation irradiance, which were 73 and 117 % of those required by Erhuacao, respectively. The optimum temperatures for cvs. Katy and Erhuacao were 25 and 35 °C in open-field and 22 and 30 °C in greenhouse, respectively. At optimal temperatures, P _N of the field-grown Katy was 16.5 μmol m⁻² s⁻¹, 21 % less than for a greenhouse-grown apricot. Both cultivars responded positively to CO₂ concentrations below the CO₂ saturation concentration, whereas Katy exhibited greater P _N (18 %) and higher carboxylation efficiency (91 %) than Erhuacao at optimal CO₂ concentration. Both cultivars exhibited greater photosynthesis in solar-heated greenhouses than in open-field, but Katy performed better than Erhuacao under greenhouse conditions.     

Comparison of Some Photosynthetic Characters Between Two Hybrid Rice Combinations Differing in Yield Potential

Photosynthetic characteristics of two hybrid rice combinations, Peiai 64S/E32 and Shanyou 63, were compared at the panicle differentiation stage. As compared with Shanyou 63, the new combination Peiai 64S/E32 showed a significantly higher net photosynthetic rate (P _N), apparent quantum yield of carbon assimilation (_c), carboxylation efficiency (CE), and photorespiratory rate (R _P) as well as leaf chlorophyll content, but a significantly lower dark respiration rate (R _D) and compensation irradiance (I _c). It also showed a slightly higher photochemical efficiency (F_v/F_m and F/F_m) of photosystem 2, a lower non-photochemical quenching (q_N), and a similar CO₂ compensation concentration () as compared to Shanyou 63.     

Photosynthetic Characteristics in Mulberry during Water Stress and Rewatering

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 (W) 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.     

Determinant of photosynthetic capacity in rice leaves under ambient air conditions

At the grain-filling stage, net photosynthetic rate (P _N), stomatal conductance (g _s), and ribulose-1,5-bisphosphate carboxylation efficiency (CE) were correlated in order to find the determinant of photosynthetic capacity in rice leaves. For a flag leaf, P _N in leaf middle region was higher than in its upper region, and leaf basal region had the lowest P _N value. The differences in g _s and CE were similar. P _N, g _s, and CE gradually declined from upper to basal leaves, showing a leaf position gradient. The correlation coefficient between P _N and CE was much higher than that between P _N and g _s in both cases, and P _N was negatively correlated with intercellular CO₂ concentration (C _i). Hence the carboxylation activity or activated amount of ribulose-1,5-bisphosphate carboxylase/oxygenase rather than g_s was the determinant of the photosynthetic capacity in rice leaves. In addition, in flag leaves of different tillers P _N was positively correlated with g _s, but negatively correlated with C _i. Thus g _s is not the determinant of the photosynthetic capacity in rice leaves.The study was supported by the State Key Basic Research and Development Plan (No.G1998010100).     

Effects of Reddening of Cotton (Gossypium hirsutum L.) Leaves on Functional Activity of Photosynthetic Apparatus

Strong inhibition of rates of CO₂ assimilation and transpiration, stomatal conductance, and water use efficiency as well as photosystem 2 (PS2) photochemical activity were related to the severity of reddening. The inhibition of photosynthesis in red cotton leaves was due to both decreased photochemical activity and stomatal limitation. Lowered photosynthetic capacity could be one of the main factors of reduced yield in reddening cotton.     

Variation in Photosynthetic Characteristics and Leaf Area Contributes to Spathiphyllum Cultivar Differences in Biomass Production

Three genetically related Spathiphyllum cultivars, Claudia, Double Take, and Petite with similar initial sizes and biomass, were grown in a shaded greenhouse and fertilized with a constant supply of nitrogen at 200 g m^–3 using an ebb-and-flow fertigation system. Seven months later, Claudia and Double Take had plant sizes and biomasses significantly greater than Petite. Stomatal conductances of Claudia and Double Take were 30 % greater, thus net photosynthetic rates (P _N) were significantly higher than in Petite. In addition, the leaf areas (LA) of Claudia and Double Take were 60 % larger than of Petite. Since P _N was expressed per leaf surface area, the greater the LA was, the more CO₂ was fixed. Thus, the differences in plant size and biomass production of Claudia and Double Take compared to Petite are attributed to high P _N and increased LA.     

Influence of Cadmium and Zinc on Growth and Photosynthesis of Bacopa monniera Cultivated in vitro

This study evaluates the impact of cadmium and zinc interaction on the amount of soluble proteins, CO₂ fixati stomatal conductance and intercellular CO₂ contents in regenerants of B. monniera. The regenerants were grown 16 weeks on MS medium containing cadmium and zinc in various concentrations. Cadmium decreased the stom conductance, photosynthetic rate and root growth but increased the protein content. Additional supply of zinc in medium reduced the adverse effects of cadmium on these parameters.     

Interactions of Elevated CO2 Concentration and Drought Stress on Photosynthesis in Eucalyptus Cladocalyx F. Muell

Response of net photosynthetic rate (P _N), stomatal conductance (g _s), intercellular CO₂ concentration (c _i), and photosynthetic efficiency (F_v/F_m) of photosystem 2 (PS2) was assessed in Eucalyptus cladocalyx grown for long duration at 800 (C₈₀₀) or 380 (C₃₈₀) μmol mol^-1 CO₂ concentration under sufficient water supply or under water stress. The well-watered plants at C₈₀₀ showed a 2.2 fold enhancement of P _N without any change in g _s. Under both C₈₀₀ and C₃₈₀, water stress decreased P _N and g _s significantly without any substantial reduction of c _i, suggesting that both stomatal and non-stomatal factors regulated P _N. However, the photosynthetic efficiency of PS2 was not altered. This revised version was published online in June 2006 with corrections to the Cover Date.     

Photosynthetic response of Podophyllum hexandrum Royle from different altitudes in Himalayan ranges

Plants of Podophyllum hexandrum, collected from lower, mid, and upper distribution limits in alpine Himalaya were studied under greenhouse conditions to evaluate the photosynthetic response. Net photosynthetic rates (P _N), stomatal conductance (g _s), and efficiency of carbon uptake increased with altitude. The maximum P _N and g _s were measured in the considered population during the 3–6^th week of development. P _N and g _s decreased on an average by 58 and 48 % from maximum rates reached around 4^th week to the 10^th week of growth, respectively. The photosynthetic response in the three ecotypes appeared to be genetically controlled.     

Interrelationships Between Nitrogen Supply and Photosynthetic Parameters in Vicia faba L.

We determined for Vicia faba L the influence of nitrogen uptake and accumulation on the values of photon saturated net photosynthetic rate (P _Nmax), quantum yield efficiency (), intercellular CO₂ concentration (C _i), and carboxylation efficiency (C _e). As leaf nitrogen content (N_L) increased, the converged onto a maximum asymptotic value of 0.0664±0.0049 mol(CO₂) mol(quantum)^–1. Also, as N_L increased the C _i value fell to an asymptotic minimum of 115.80±1.59 mol mol^–1, and C _e converged onto a maximum asymptotic value of 1.645±0.054 mol(CO₂) m^–2 s^–1 Pa^–1 and declined to zero at a N_L-intercept equal to 0.596±0.096 g(N) m^–2. fell to zero for an N_L-intercept of 0.660±0.052 g(N) m^–2. As N_L increased, the value of P _Nmax converged onto a maximum asymptotic value of 33.400±2.563 mol(CO₂) m^–2 s^–1. P _N fell to zero for an N_L-intercept of 0.710±0.035 g(N) m^–2. Under variable daily meteorological conditions the values for N_L, specific leaf area (_L), root mass fraction (R_f), P _Nmax, and remained constant for a given N supply. A monotonic decline in the steady-state value of R_f occurred with increasing N supply. _L increased with increasing N supply or with increasing N_L.     

Leaf Photosynthesis in Eight Almond Tree Cultivars

Response of gas exchange traits to irradiance were studied in eight almond tree (Prunus amygdalus) cultivars: Desmayo Largueta, Falsa Barese, Garrigues, Lauranne, Marcona, Masbovera, Nonpareil and Ramillete, grafted on a hybrid rootstock almond × peach GF-677. From these responses cultivars can be classified from the best to the worst photosynthetic performance as follows: Falsa Barese, Masbovera, Marcona, Nonpareil, Ramillete, Desmayo Largueta, Lauranne and Garrigues. The highest net photosynthetic rate was 20.3 μmol m⁻² s⁻¹ in Falsa Barese. In the absence of water stress, photosynthetic rate was not limited by stomatal conductance. Consequently, non-stomatal limitations prevailed under such conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of water stress and nitrogen supply on leaf gas exchange and fluorescence parameters of <Emphasis Type="Italic">Sophora davidii</Emphasis> seedlings

Two-month-old seedlings of Sophora davidii were subjected to a randomized complete block design with three water (80, 40, and 20 % of water field capacity, i.e. FC₈₀, FC₄₀, and FC₂₀) and three N supply [N0: 0, Nl: 92 and Nh: 184 mg(N) kg⁻¹(soil)] regimes. Water stress produced decreased leaf area (LA) and photosynthetic pigment contents, inhibited photosynthetic efficiency, and induced photodamage in photosystem 2 (PS2), but increased specific leaf area (SLA). The decreased net photosynthetic rate (P _N) under medium water stress (FC₄₀) compared to control (FC₈₀) might result from stomatal limitations, but the decreased P _N under severe water deficit (FC₂₀) might be attributed to non-stomatal limitations. On the other hand, N supply could improve photosynthetic capacity by increasing LA and photosynthetic pigment contents, and enhancing photosynthetic efficiency under water deficit. Moreover, N supply did a little in alleviating photodamages to PS2 caused by water stress. Hence water stress was the primary limitation in photosynthetic processes of S. davidii seedlings, while the photosynthetic characters of seedlings exhibited positive responses to N supply. Appropriate N supply is recommended to improve photosynthetic efficiency and alleviate photodamage under water stress.