Plant Responses to Salinity Under Elevated Atmospheric Concentrations of CO2

1992 ◽  
Vol 40 (5) ◽  
pp. 515 ◽  
Author(s):  
MC Ball ◽  
R Munns
Keyword(s):  
Water Use Efficiency ◽  
Elevated Co2 ◽  
Water Use ◽  
Water Loss ◽  
Salt Flux ◽  
Carbon Gain ◽  
Salt Balance ◽  
Salt Uptake ◽  
Use Efficiency ◽  
Atmospheric Concentrations

This review explores effects of elevated CO2 concentrations on growth in relation to water use and salt balance of halophytic and non-halophytic species. Under saline conditions, the uptake and distribution of sodium and chloride must be regulated to protect sensitive metabolic sites from salt toxicity. Salt-tolerant species exclude most of the salt from the transpiration stream, but the salt flux from a highly saline soil is still considerable. To maintain internal ion concentrations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt storage and/or salt export by either retranslocation or secretion from glands. Hence the balance between carbon gain and the expenditure of water in association with salt uptake is critical to leaf longevity under saline conditions. Indeed, one of the striking features of halophytic vegetation, such as mangroves, is the maintenance of high water use efficiencies coupled with relatively low rates of water loss and growth. These low evaporation rates are further reduced under elevated CO2 conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants grown under elevated CO2 conditions might be expected to contain lower salt concentrations than those grown under ambient CO2 if salt uptake is coupled with water uptake. However, salt concentrations in shoot tissues are similar in plants grown under ambient and elevated CO2 conditions despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in both C3 and C2 non-halophytes. These results imply shoot/root communication in regulation of the salt balance to adjust to environmental factors affecting the availability of water and ions at the roots (salinity) and those affecting carbon gain in relation to water loss at the leaves (atmospheric concentrations of water vapour and carbon dioxide).

scholarly journals Costs and benefits of photosynthetic stems in desert species from southern California

2019 ◽  
Vol 46 (2) ◽  
pp. 175 ◽  
Author(s):  
Eleinis Ávila-Lovera ◽  
Roxana Haro ◽  
Exequiel Ezcurra ◽  
Louis S. Santiago
Keyword(s):  
Isotopic Composition ◽  
Water Use Efficiency ◽  
Water Use ◽  
Water Loss ◽  
Water Status ◽  
Carbon Isotopic Composition ◽  
Carbon Gain ◽  
Costs And Benefits ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency

Woody plants with green photosynthetic stems are common in dry woodlands with the possible advantages of extra carbon gain, re-assimilation of CO2, and high water-use efficiency. However, their green stem tissue may also incur greater costs of water loss when stomata are closed. Our study focussed on evaluating the costs and benefits of having green stems in desert plants, addressing the water-use efficiency hypothesis. We measured water status, carbon and water exchange, and carbon, nitrogen and oxygen isotopic composition of 15 species in a desert wash scrub in Joshua Tree National Park, California, USA. We found that all woody species that have green stems relied on their green stems as the sole organ for carbon assimilation for most of the study period. Green stems had similar photosynthetic rate (Amax), stomatal conductance (gs) and intrinsic water-use efficiency (WUEi) to leaves of the same species. However, Amax, gs and cuticular conductance (gmin) were higher in green stems than in leaves of non-green stemmed species. Carbon isotopic composition (δ13C) was similar in both leaves and green stems, indicating no difference in integrated long-term WUE. Our results raise questions about the possible trade-off between carbon gain and water loss through the cuticle in green stems and how this may affect plant responses to current and future droughts.

Salinity Tolerance in the Mangroves Aegiceras corniculatum and Avicennia marina. I. Water Use in Relation to Growth, Carbon Partitioning, and Salt Balance

1988 ◽  
Vol 15 (3) ◽  
pp. 447 ◽  
Author(s):  
MC Ball
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Avicennia Marina ◽  
Carbon Partitioning ◽  
Salt Flux ◽  
Salt Balance ◽  
Aegiceras Corniculatum ◽  
Increase With Increase ◽  
Salt Exclusion ◽  
Use Efficiency

The water use characteristics of two mangrove species, Aegiceras corniculatum and Avicennia marina, in salinities of 50, 250 and 500 mol m-3 NaCI and leaf-to-air vapour pressure differences of 6, 12 and 24 mbar were studied in relation to growth, carbon partitioning and salt balance. The net water use efficiency in A. corniculatum declined with increasing salinity and decreasing humidity. In contrast, water use was more conservative in A. marina, which maintained the net water use efficiency almost constant with variation in salinity. Aegiceras corniculatum maintained higher rates of water uptake and higher leaf area/plant mass ratios than A. marina. Growth of both species declined with increasing salinity, with A. corniculatum being the more sensitive species. Differences in growth rates between species and between treatments were consistent with differences in the assimilation rate and leaf areal plant mass ratio. Salt exclusion by both species increased from 90 to 97% with increase in salinity from 50 to 500 mol m-3 NaCl. The xylem Cl- concentrations increased with increase in salinity, but decreased with increase in shoot evaporation rates such that the salt flux to the leaves did not increase with increase in evaporation rates at a given salinity. Despite similarities in the salt fluxes to leaves, the transport of Cl- to the shoot per unit of shoot growth increased more with increasing salinity in A. corniculatum than in A. marina because the net water use efficiencies were lower in the former species. Thus, the amount of salt secreted per mole water transpired (and hence also per mole carbon gained) increased more with increasing salinity in A. corniculatum than in A. marina. These differences in salt balance may be associated with the greater sensitivity of A. corniculaturn to increasing salinity. The possible ecological significance of these findings is discussed.

Does Elevated CO2 Affect the Physiology and Growth of Quercus Mongolica under Different Nitrogen Conditions?

2005 ◽  
Vol 277-279 ◽  
pp. 528-535
Author(s):  
Oh Hyun Kyung ◽  
Yeonsook Choung
Keyword(s):  
Water Use Efficiency ◽  
Elevated Co2 ◽  
Water Use ◽  
Physiological Activity ◽  
Photosynthesis Rate ◽  
Total Biomass ◽  
High Nitrogen ◽  
Quercus Mongolica ◽  
Use Efficiency ◽  
Nitrogen Conditions

The response of Quercus mongolica, one of the major tree species in Northeast Asia and the most dominant deciduous tree in Korea, was studied in relation to elevated CO2 and the addition of nitrogen to soil in terms of its physiology and growth over two years. Plants were grown from seed at two CO2 conditions (ambient and 700 µL L-1) and with two levels of soil nitrogen supply (1.5 mM and 6.5 mM). Elevated CO2 was found to significantly enhance the photosynthesis rate and water use efficiency by 2.3-2.7 times and by 1.3-1.8 times, respectively. Over time within a growing season, there was a decreasing trend in the photosynthesis rate. However, the decrease was slower especially in two-year-old seedlings grown in elevated CO2 and high nitrogen conditions, suggesting that their physiological activity lasted relatively longer. Improved photosynthesis and water use efficiency as well as prolonged physiological activity under high CO2 condition resulted in an increase in biomass accumulation. That is, in elevated CO2, total biomass increased by 1.7 and 1.2 times, respectively, for one- and two-year-old seedlings with low nitrogen conditions, and by 1.8 and 2.6 times with high nitrogen conditions. This result indicates that the effect of CO2 on biomass is more marked in high nitrogen conditions. This, therefore, shows that the effect of CO2 is accelerated by the addition of nitrogen. With the increase in total biomass, the number of leaves and stem diameter increased significantly, and more biomass was allocated in roots, resulting in structural change. Overall, the elevated CO2 markedly stimulated the physiology and growth of Q. mongolica. This demonstrates that Q. mongolica is capable of exploiting an elevated CO2 environment. Therefore, it will remain a dominant species and continue to be a major CO2 sink in the future, even though other resources such as nitrogen can modify the CO2 effect.

Water Use Efficiency as a Constraint and Target for Improving the Resilience and Productivity of C3and C4Crops

2019 ◽  
Vol 70 (1) ◽  
pp. 781-808 ◽  
Author(s):  
Andrew D.B. Leakey ◽  
John N. Ferguson ◽  
Charles P. Pignon ◽  
Alex Wu ◽  
Zhenong Jin ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Crop Production ◽  
Crop Improvement ◽  
Canopy Structure ◽  
Complex Trait ◽  
Carbon Gain ◽  
Crop Development ◽  
Component Traits ◽  
Use Efficiency

The ratio of plant carbon gain to water use, known as water use efficiency (WUE), has long been recognized as a key constraint on crop production and an important target for crop improvement. WUE is a physiologically and genetically complex trait that can be defined at a range of scales. Many component traits directly influence WUE, including photosynthesis, stomatal and mesophyll conductances, and canopy structure. Interactions of carbon and water relations with diverse aspects of the environment and crop development also modulate WUE. As a consequence, enhancing WUE by breeding or biotechnology has proven challenging but not impossible. This review aims to synthesize new knowledge of WUE arising from advances in phenotyping, modeling, physiology, genetics, and molecular biology in the context of classical theoretical principles. In addition, we discuss how rising atmospheric CO2concentration has created and will continue to create opportunities for enhancing WUE by modifying the trade-off between photosynthesis and transpiration.

Diurnal Time Course of Leaf Gas Exchange Rates and Related Characters in Drought-Acclimated and Irrigated Trifolium Subterraneum.

1995 ◽  
Vol 22 (3) ◽  
pp. 461 ◽  
Author(s):  
J Vadell ◽  
C Cabot ◽  
H Medrano
Keyword(s):  
Gas Exchange ◽  
Exchange Rates ◽  
Water Use Efficiency ◽  
Water Use ◽  
Leaf Gas Exchange ◽  
Trifolium Subterraneum ◽  
Co2 Assimilation ◽  
Carbon Gain ◽  
Assimilation Rate ◽  
Use Efficiency

The effects of drought acclimation on the diurnal time courses of photosynthesis and related characters were studied in Trifolium subterraneum L. leaves during two consecutive late spring days. Leaf CO2 assimilation rate and transpiration rate followed irradiance variations in irrigated plants. Under drought, a bimodal pattern of leaf CO2 assimilation rate developed although stomatal conductance remained uniform and low. Instantaneous water-use efficiency was much higher in droughted plants during the early morning and late evening, while during the middle of the day it was close to the value of irrigated plants. Net carbon gain in plants under drought reached 40% of the carbon gain in irrigated plants with a significant saving of water (80%). Average data derived from midday values of leaf CO2 assimilation rates and instantaneous water-use efficiency did not provide good estimates of the daily carbon gain and water-use efficiency for droughted leaves. Coupled with the morphological changes as a result of acclimation to progressive drought, modifications of diurnal patterns of leaf gas exchange rates effectively contribute to a sustained carbon gain during drought. These modifications significantly improve water-use efficiency, mainly by enabling the plant to take advantage of morning and evening hours with high air humidity.

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