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 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.

Genetic variation in tolerance to the osmotic stress componentof salinity stress in durum wheat

2008 ◽  
Vol 35 (2) ◽  
pp. 111 ◽  
Author(s):  
Richard A. James ◽  
Susanne von Caemmerer ◽  
A. G. (Tony) Condon ◽  
Alexander B. Zwart ◽  
Rana Munns
Keyword(s):  
Genetic Variation ◽  
Stomatal Conductance ◽  
Osmotic Stress ◽  
Durum Wheat ◽  
Co2 Assimilation ◽  
Saline Soils ◽  
Assimilation Rate ◽  
Relative Growth ◽  
Co2 Assimilation Rate ◽  
Excessive Accumulation

Salinity affects plant growth by the osmotic stress of the salt around the roots as well as by toxicity caused by excessive accumulation of salt in leaves. The aim of this study was to determine whether there is significant genetic variation in tolerance to osmotic stress that can be useful in improving the salinity tolerance of crop plants. Durum wheat is a salt-sensitive crop whose yield is reduced by moderately saline soils. Genetic variation in tolerance to osmotic stress in durum wheat was examined in 50 international durum varieties and landraces by measuring the response of stomatal conductance to salt stress before salts built up in the leaf. Stomatal conductance is a sensitive indicator of the osmotic stress because it is reduced immediately with the onset of salinity, and is the initial and most profound cause of a decline in CO2 assimilation rate. Genetic differences of 2–3-fold were found in the magnitude of the response of stomatal conductance to salt-induced osmotic stress. Higher stomatal conductance in salt related to higher CO2 assimilation rate. There was a positive relationship between stomatal conductance and relative growth rate in salt. This study shows the potential for new genetic gains in salt tolerance in durum wheat.

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.

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 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.

A consistent CO2 assimilation rate and an enhanced root development drives the tolerance mechanism in Ziziphus jujuba under soil water deficit

2020 ◽  
Vol 34 (4) ◽  
pp. 392-404 ◽  
Author(s):  
Muhammad Azeem Sabir ◽  
Fahad Rasheed ◽  
Zikria Zafar ◽  
Imran Khan ◽  
Muhammad Farrakh Nawaz ◽  
...  
Keyword(s):  
Soil Water ◽  
Water Deficit ◽  
Root Development ◽  
Co2 Assimilation ◽  
Soil Water Deficit ◽  
Assimilation Rate ◽  
Tolerance Mechanism ◽  
Co2 Assimilation Rate ◽  
Ziziphus Jujuba
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