Effects of salinity on gas exchange, water relations and growth of sunflower (Helianthus annuus)

2002 ◽  
Vol 29 (12) ◽  
pp. 1405 ◽  
Author(s):  
Anna Rita Rivelli ◽  
Stella Lovelli ◽  
Michele Perniola
Keyword(s):  
Electrical Conductivity ◽  
Salt Stress ◽  
Gas Exchange ◽  
Helianthus Annuus ◽  
Water Relations ◽  
Co2 Assimilation ◽  
Ionic Concentration ◽  
Assimilation Rate ◽  
Co2 Assimilation Rate ◽  
Salinity Levels

The aim of this study was to determine the response of sunflower (Helianthus annuus L. cv. Romsum HS90) to salinity in terms of gas exchange, ionic and water relations, and growth. Experiments were carried out in the glasshouse, where sunflower plants were exposed to increasing salinity levels using water with a wide range of electrical conductivity (0.39–20 dS m–1) to provide different degrees of salt stress. The CO2 assimilation rate (A), stomatal conductance and plant aboveground dry weight (DW) significantly decreased as electrical conductivity of the soil increased. The decline in photosynthesis measured in response to salt stress was proportionally greater than the decline in transpiration, resulting in a reduction of water use efficiency, at both the leaf and whole-plant levels. Among the factors inhibiting photosynthetic activity, those of a non-stomatal nature had a greater effect. In particular, an analysis of photosynthetic CO2 assimilation rate vs intercellular CO2 concentration (A vs Ci curves) indicated a reduction in activity of Rubisco (EC 4.1.1.39) as salinity levels increased. Under severe salt-stress conditions, chlorophyll fluorescence showed a slowing of electron transport at the PSII level. Salt accumulation in the rhizosphere caused a reduction in tissue water status that was partly associated with a decline in osmotic potential (Ψπ). Leaf ionic concentration was clearly correlated with values of leaf Ψπ. However, leaf ionic concentration showed discontinuous distribution between younger and older leaves, reflecting a strategy of plants to preserve younger and more metabolically-active leaves from accumulating salt to toxic levels.

scholarly journals Salt tolerance and regulation of gas exchange and hormonal homeostasis by auxin-priming in wheat

2013 ◽  
Vol 48 (9) ◽  
pp. 1210-1219 ◽  
Author(s):  
Muhammad Iqbal ◽  
Muhammad Ashraf
Keyword(s):  
Abscisic Acid ◽  
Gas Exchange ◽  
Acid Concentration ◽  
Spring Wheat ◽  
Indoleacetic Acid ◽  
Co2 Assimilation ◽  
Assimilation Rate ◽  
Co2 Assimilation Rate ◽  
Net Co2 Assimilation Rate ◽  
Net Co2 Assimilation

The objective of this work was to assess the regulatory effects of auxin-priming on gas exchange and hormonal homeostasis in spring wheat subjected to saline conditions. Seeds of MH-97 (salt-intolerant) and Inqlab-91 (salt-tolerant) cultivars were subjected to 11 priming treatments (three hormones x three concentrations + two controls) and evaluated under saline (15 dS m-1) and nonsaline (2.84 dS m-1) conditions. The priming treatments consisted of: 5.71, 8.56, and 11.42 × 10-4 mol L-1 indoleacetic acid; 4.92, 7.38, and 9.84 × 10-4 mol L-1 indolebutyric acid; 4.89, 7.34, and 9.79 × 10-4 mol L-1 tryptophan; and a control with hydroprimed seeds. A negative control with nonprimed seeds was also evaluated. All priming agents diminished the effects of salinity on endogenous abscisic acid concentration in the salt-intolerant cultivar. Grain yield was positively correlated with net CO2 assimilation rate and endogenous indoleacetic acid concentration, and it was negatively correlated with abscisic acid and free polyamine concentrations. In general, the priming treatment with tryptophan at 4.89 × 10-4 mol L-1 was the most effective in minimizing yield losses and reductions in net CO2 assimilation rate, under salt stress conditions. Hormonal homeostasis increases net CO2 assimilation rate and confers tolerance to salinity on spring wheat.

Shade tree species affect gas exchange and hydraulic conductivity of cacao cultivars in an agroforestry system

2020 ◽  
Author(s):  
Eleinis Ávila-Lovera ◽  
Héctor Blanco ◽  
Olga Móvil ◽  
Louis S Santiago ◽  
Wilmer Tezara
Keyword(s):  
Hydraulic Conductivity ◽  
Stomatal Conductance ◽  
Gas Exchange ◽  
Co2 Assimilation ◽  
Agroforestry System ◽  
Timber Species ◽  
Positive Contribution ◽  
Assimilation Rate ◽  
Co2 Assimilation Rate ◽  
Carbon Economy

Abstract Shade tolerance is a widespread strategy of rainforest understory plants. Many understory species have green young stems that may assimilate CO2 and contribute to whole-plant carbon balance. Cacao commonly grows in the shaded understory and recent emphasis has been placed on diversifying the types of trees used to shade cacao plants to achieve additional ecosystem services. We studied three agricultural cacao cultivars growing in the shade of four timber species (Cedrela odorata L., Cordia thaisiana Agostini, Swietenia macrophylla King and Tabebuia rosea (Bertol) A.D.C.) in an agroforestry system to (i) evaluate the timber species for their effect on the physiological performance of three cacao cultivars; (ii) assess the role of green stems on the carbon economy of cacao; and (iii) examine coordination between stem hydraulic conductivity and stem photosynthesis in cacao. Green young stem photosynthetic CO2 assimilation rate was positive and double leaf CO2 assimilation rate, indicating a positive contribution of green stems to the carbon economy of cacao; however, green stem area is smaller than leaf area and its relative contribution is low. Timber species showed a significant effect on leaf gas exchange traits and on stomatal conductance of cacao, and stem water-use efficiency varied among cultivars. There were no significant differences in leaf-specific hydraulic conductivity among cacao cultivars, but sapwood-specific hydraulic conductivity varied significantly among cultivars and there was an interactive effect of cacao cultivar × timber species. Hydraulic efficiency was coordinated with stem-stomatal conductance, but not with leaf-stomatal conductance or any measure of photosynthesis. We conclude that different shade regimes determined by timber species and the interaction with cacao cultivar had an important effect on most of the physiological traits and growth variables of three cacao cultivars growing in an agroforestry system. Results suggested that C. odorata is the best timber species to provide partial shade for cacao cultivars in the Barlovento region in Venezuela, regardless of cultivar origin.

scholarly journals Morphophysiology of the passion fruit ‘BRS Rubi do Cerrado’ irrigated with saline waters and nitrogen fertilization

2020 ◽  
Vol 12 ◽  
pp. e3456
Author(s):  
Alzira Maria de Sousa Silva Neta ◽  
Lauriane Almeida dos Anjos Soares ◽  
Geovani Soares de Lima ◽  
Luderlandio de Andrade Silva ◽  
Fagner Nogueira Ferreira ◽  
...  
Keyword(s):  
Irrigation Water ◽  
Nitrogen Fertilization ◽  
Co2 Assimilation ◽  
Passion Fruit ◽  
Water Salinity ◽  
Assimilation Rate ◽  
Co2 Assimilation Rate ◽  
Irrigation Water Salinity ◽  
Salinity Levels ◽  
Purple Passion Fruit

This study aimed to evaluate the gas exchanges and growth of the purple passion fruit cultivar ‘BRS Rubi do Cerrado’ as a function of the salinity levels of the irrigation water and nitrogen fertilization. The research was conducted in pots adapted as drainage lysimeters, placed within a plant nursery, using a Regolithic Neosol of sandy texture, in the municipality of Pombal-PB, Brazil. A randomized block design was used, testing five levels of electrical conductivity of irrigation water (0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) associated with four doses of nitrogen (50, 75, 100, and 125% of the recommendation). The irrigation water salinity above 0.3 dS m-1 compromised the leaf area and the relative water content of the purple passion fruit ‘BRS Rubi do Cerrado’. High doses of nitrogen enhance the deleterious effects of irrigation water salinity on stomatal conductance, transpiration, internal CO2 concentration, CO2 assimilation rate, number of leaves, stem diameter, and height of purple passion fruit plants. When waters with salinity levels of up to 1.3 dS m-1 are used, the dose of 125 mg of N kg-1 of soil is recommendation for providing increases in the CO2 assimilation rate of the purple passion fruit ‘BRS Rubi do Cerrado’ at 70 days after sowing (DAS). Water salinity increases electrolyte leakage, regardless of nitrogen doses.

scholarly journals Water status, cell damage and gas exchanges in West Indian cherry (Malpighia emarginata) under salt stress and nitrogen fertilization

2020 ◽  
pp. 319-324
Author(s):  
Geovani Soares de Lima ◽  
Francisco Wesley Alves Pinheiro ◽  
Adaan Sudário Dias ◽  
Hans Raj Gheyi ◽  
Saulo Soares da Silva ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Sandy Loam ◽  
Cell Damage ◽  
Water Status ◽  
West Indian ◽  
Co2 Assimilation ◽  
Assimilation Rate ◽  
Water Saturation Deficit ◽  
Gas Exchanges ◽  
Co2 Assimilation Rate

This study was conducted to evaluate water status, cell damage and gas exchanges of West Indian cherry grown under saline water irrigation and nitrogen (N) fertilization in the post-grafting stage. The experiment was carried out in drainage lysimeters under greenhouse conditions in Regolithic Neosol with sandy loam texture. Treatments consisted of two levels of electrical conductivity of water (ECw) (0.8 and 4.5 dS m-1) and four N doses (70; 85; 100 and 115% of the N recommendation), arranged in randomized blocks, with three replicates. The dose relative to 100% corresponded to 200 g of N per plant per year. Irrigation with 4.5 dS m-1 electrical conductivity water resulted in a reduction in stomatal conductance, transpiration, CO2 assimilation rate and instantaneous carboxylation efficiency but increased cell damage percentage and internal CO2 concentration in West Indian cherry plants. Inhibition of CO2 assimilation rate in West Indian cherry plants is related to non-stomatal effects. Irrigation with 4.5 dS m-1 water and fertilization with 115% of N recommendation intensified leaf water saturation deficit in the West Indian cherry crop. The BRS Jaburu West Indian cherry was sensitive to 4.5 dS m-1 water salinity.

Relationship Between Steady-State Gas Exchange, in vivo Ribulose Bisphosphate Carboxylase Activity and Some Carbon Reduction Cycle Intermediates in Raphanus sativus

1986 ◽  
Vol 13 (5) ◽  
pp. 669 ◽  
Author(s):  
SV Caemmerer ◽  
DL Edmondson
Keyword(s):  
Gas Exchange ◽  
Co2 Assimilation ◽  
Assimilation Rate ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
High Co2 ◽  
Co2 Assimilation Rate ◽  
Low Co2 ◽  
Pool Sizes

The relationships between CO2 assimilation rate, RuP2 carboxylase activity and sizes of the pools of ribulose 1,5-bisphosphate (RuP2) and 3-phosphoglyceric acid (PGA) were examined using a freeze clamp device to rapidly freeze sections of attached leaves of R. sativus which previously had gas-exchange measurements made on them. At high irradiance and ambient partial pressures of CO2 and O2, RuP2 carboxylase was fully active in vivo. Activity was less at very low CO2 pressures and at high CO2 pressures, particularly when combined with low O2 pressures. In vivo RuP2 carboxylase activity and both RuP2 and PGA pool sizes increased with increasing irradiance. RuP2 pool sizes were high at low CO2 pressures and decreased at high CO2 pressures. PGA pool sizes, on the other hand, were low at low CO2 and high at high CO2 pressures. A model of RuP2 carboxylase-oxygenase (Rubisco) kinetics is used to examine the quantitative relationship between in vivo RuP2 carboxylase activity, CO2 assimilation rate and RuP2 and PGA pools. The model predictions fit in vivo data, except at high CO2 pressures, if it is assumed that RuP2 does not bind tightly to the inactive enzyme form in vivo. It is shown that a large fraction of the RuP2 and PGA pools may be chelated by magnesium in the stroma and that the high RuP2 pools (e.g. at low irradiance) may represent an optimal concentration rather than be truly saturating. We conclude that RuP2 pool sizes above Rubisco site concentration do not necessarily indicate a Rubisco limitation of photosynthetic rate.

scholarly journals Salinity Stress Affects Photosynthesis, Malondialdehyde Formation, and Proline Content in Portulaca oleracea L.

Plants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 845
Author(s):  
Helena Hnilickova ◽  
Kamil Kraus ◽  
Pavla Vachova ◽  
Frantisek Hnilicka
Keyword(s):  
Salt Stress ◽  
Water Potential ◽  
Co2 Concentration ◽  
Co2 Assimilation ◽  
Proline Content ◽  
Portulaca Oleracea ◽  
Control Group ◽  
Malondialdehyde Formation ◽  
Salinity Levels ◽  
Mda Content

In this investigation, the effect of salt stress on Portulaca oleracea L. was monitored at salinity levels of 100 and 300 mM NaCl. At a concentration of 100 mM NaCl there was a decrease in stomatal conductance (gs) simultaneously with an increase in CO2 assimilation (A) at the beginning of salt exposure (day 3). However, the leaf water potential (ψw), the substomatal concentration of CO2 (Ci), the maximum quantum yield of photosystem II (Fv/Fm), and the proline and malondialdehyde (MDA) content remained unchanged. Exposure to 300 mM NaCl caused a decrease in gs from day 3 and a decrease in water potential, CO2 assimilation, and Fv/Fm from day 9. There was a large increase in proline content and a significantly higher MDA concentration on days 6 and 9 of salt stress compared to the control group. After 22 days of exposure to 300 mM NaCl, there was a transition from the C4 cycle to crassulacean acid metabolism (CAM), manifested by a rapid increase in substomatal CO2 concentration and negative CO2 assimilation values. These results document the tolerance of P. oleracea to a lower level of salt stress and the possibility of its use in saline localities.

scholarly journals Foliar phosphorus supply and CO2 assimilation in common bean (Phaseolus vulgaris L.) under water deficit

2006 ◽  
Vol 18 (3) ◽  
pp. 407-411 ◽  
Author(s):  
Mauro G. dos Santos ◽  
Rafael V. Ribeiro ◽  
Marcelo G. Teixeira ◽  
Ricardo F. de Oliveira ◽  
Carlos Pimentel
Keyword(s):  
Phaseolus Vulgaris ◽  
Common Bean ◽  
Water Deficit ◽  
Co2 Assimilation ◽  
Assimilation Rate ◽  
Phaseolus Vulgaris L ◽  
Co2 Assimilation Rate ◽  
Net Co2 Assimilation ◽  
Foliar Phosphorus ◽  
Regulation Of Photosynthesis

Two common bean cultivars were grown in pots under greenhouse conditions. Plants were submitted to a foliar Pi spray two days before suspending irrigation, what enhanced net CO2 assimilation rate of Ouro Negro cultivar but did not change significantly the photosynthesis of Carioca cultivar under both water deficit and rehydration periods. The results revealed that a foliar Pi spray induced an up-regulation of photosynthesis in common bean under mild water deficit, with this effect being genotype-dependent.

scholarly journals Effects of water deficit on growth and physiology of young Conocarpus erectus L. and Ficus benjamina L. Saplings

2019 ◽  
Vol 48 (4) ◽  
pp. 1215-1221
Author(s):  
Zikria Zafar ◽  
Fahad Rasheed ◽  
Muhammad Abdullah ◽  
Mir Md Abdus Salam ◽  
Muhammad Mohsin
Keyword(s):  
Water Deficit ◽  
Biomass Production ◽  
Root Biomass ◽  
Growth Parameters ◽  
Co2 Assimilation ◽  
Total Biomass ◽  
Assimilation Rate ◽  
Ficus Benjamina ◽  
Co2 Assimilation Rate ◽  
Conocarpus Erectus

A greenhouse experiment was conducted to investigate the effects of water deficit on growth and physiological parameters of Ficus benjamina and Conocarpus erectus. The results revealed that all growth parameters such as plant height, stem diameter, no. of leaves, no. of branches and chlorophyll contents significantly decreased under water deficit condition. Interestingly, although leaf, stem and total biomass production and allocation decreased significantly under water deficit, but root biomass production and allocation increased significantly. Similarly, stomatal conductance to water vapor decreased significantly and CO2 assimilation rate remained similar to control under water deficit condition. Resultantly, a significant increase in water use efficiency was evident in both species under water deficit condition. These results suggested that, in spite of a significant decrease in biomass production, young Conocarpus erectus and Ficus benjamina can tolerate water deficit which is due to sustained CO2 assimilation rate and increase in root biomass.

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