The Effect of Decreasing Water Potential on Net CO2 Exchange of Intact Desert Shrubs

Odening, W. R.; Strain, Boyd R.; Oechel, Walter C.

doi:10.2307/1940358

Cited by 90 publications

(64 citation statements)

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“…They concluded that changes in specific leaf weight were of adaptive value in allowing these shrubs to remain active into drought periods. In a similar manner, Odening et al (18) concluded that during drought increased specific leaf weight was the factor responsible for enhanced water use efficiency. Our estimates of specific leaf mass in this study indicate that all of the increases in specific leaf mass can be attributed to increases in pubescence.…”

Section: Resultsmentioning

confidence: 82%

“…The decline in photosynthesis (A)2 with decreasing leaf water potential (A,) is often linear (1,2,7,12,(15)(16)(17)(18)(19). Both stomatal and nonstomatal components are thought to be responsible for the decreased photosynthetic rate, and several investigators (2,3,7,12,20) these studies, there was a decline in the initial slope of the CO2 dependence curve (OA/Oci, often called the carboxylation efficiency) and also a decrease in A at high ci.…”

Section: Abstracimentioning

confidence: 99%

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Photosynthesis in Encelia farinosa Gray in Response to Decreasing Leaf Water Potential

Ehleringer¹,

Cook²

1984

Plant Physiol.

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ABSTRACIPhotosynthetic responses of intact leaves of the desert shrub Ewelia farinosa were measured during a long term drought cycle in order to understand the responses of stomatal and nonstomatal components to water stress. Photosynthetic rate at high irradiance and leaf conductance to water vapor both decreased linearly with declining leaf water potential. The intercellular CO2 concentration (c,) remained fairly constant as a function of leaf water potential in plants subjected to a slow drought cycle of 25 days, but decreased in plants exposed to a 12-day drought cycle.With increasing water stress, the slope of the dependence of photosynthesis on c, (carboxylation efficiency) decreased, the maximum photosynthetic rates at high c, beame saturated at lower values, and water use efficiency increased. Both the carboxylation efficiency and photosynthetic rates were positively correlated with leaf nitrogen content. Associated with lower leaf conductances, the calculated stomatal limitation to photosynthesis increased with water stress. However, because of simultaneous changes in the dependence of photosynthesis on c, with water stress, increased leaf conductance alone in water-stressed leaves would not result in an increase in photosynthetic rates to prestressed levels. Both active osmotic adjustment and changes in specific leaf mass occurred during the drought cycle. In response to increased water stress, leaf specific mass increased. However, the increases in specific leaf mass were associated with the production of a reflective pubescence and there were no changes in specific mass of the photosynthetic tissues. The significance of these responses for carbon gain and water loss under and conditions are discussed.Net photosynthetic rate decreases as leaf water stress increases (13,14). The decline in photosynthesis (A)2 with decreasing leaf water potential (A,) is often linear (1,2,7,12,(15)(16)(17)(18)(19). Both stomatal and nonstomatal components are thought to be responsible for the decreased photosynthetic rate, and several investigators (2,3,7,12,20) these studies, there was a decline in the initial slope of the CO2 dependence curve (OA/Oci, often called the carboxylation efficiency) and also a decrease in A at high ci. Not all studies of photosynthesis during water stress have shown a decrease in the carboxylation efficiency, and in those studies it may be that the stress development was too rapid for a decrease in carboxylation efficiency to occur (13).Recently, attention has been focused on quantitatively assessing the extent to which photosynthesis is colimited by stomatal and nonstomatal components (1 1). The different limitations can be analyzed evaluating what has been called the 'supply' function (stomatal or diffusion component) and the 'demand' function (nonstomatal component). The demand function is the A versus ci response curve, and the supply function is a line with an xaxis intercept equal to the ca and a negative slope equal to a specified g'. Since the supply function defines the photosynth...

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Section: Resultsmentioning

confidence: 82%

Section: Abstracimentioning

confidence: 99%

Photosynthesis in Encelia farinosa Gray in Response to Decreasing Leaf Water Potential

Ehleringer¹,

Cook²

1984

Plant Physiol.

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“…No período seco, essas espécies perdem as folhas para evitar a perda excessiva de água (Borchert 1994;Lima & Rodal, 2010;Lima et al 2012). Em contrapartida, espécies sempre verdes mantém as folhas e as trocas gasosas mesmo sob baixos potenciais hídricos, exibindo clara tolerância ao déficit hídrico (Odening et al 1974).…”

Section: Discussionunclassified

Divergências funcionais e estratégias de resistência à seca entre espécies decíduas e sempre verdes tropicais

et al. 2015

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ResumoAnalisamos a variação funcional entre espécies decíduas (ED) e sempre verdes (ESV) para compreender as divergências nas estratégias de tolerância e evitação à seca. O estudo foi realizado em um fragmento de floresta tropical sazonalmente seca, localizada no munícipio de Pentecoste (3°47'S, 39°16'W), Ceará, Brasil. Mensuramos 17 traços funcionais foliares em 17 ED e cinco ESV, sendo 12 morfofuncionais, um fenológico e quatro fisiológicos. Verificamos que as ED exibiram maior taxa de fotossíntese por massa (A massa ), menor longevidade foliar (LF) e massa foliar específica (MFE) quando comparadas às sempre verdes. Esses traços foram considerados traços-chaves preditores das estratégias de evitação e tolerância à seca. As ED e ESV apresentaram uma demanda conflitante entre tolerância à seca e taxa fotossintética, pois a LF foi negativamente correlacionada com à A massa . Embora tenham demonstrado diferenças claras na MFE e LF não observamos diferenças significativas na A área e g s , consequentemente, ED e ESV não diferiram na eficiência no uso da água durante o período chuvoso. Apesar da variabilidade substancial dentro do grupo, todas as ED exibem estratégia de evitação à seca enquanto que ESV exibem um conjunto de traços funcionais foliares relacionados a estratégia de tolerância à seca. Palavras-chave: Grupos fenológicos, tolerância à seca, evitação à seca. AbstractWe analyzed the functional variation between deciduous and evergreen species to understand the differences across the strategies of avoidance and tolerance to drought. Our study was carried in a fragment of seasonally dry tropical forest located in the city of Pentecoste (3°47'S, 39°16'W), Ceará, Brazil. We measured 17 functional leaf traits in 17 deciduous and five evergreen species, being 12 morphofunctional, one phenological and four physiological. We found that deciduous species exhibited greater A mass , lower leaf lifespan (LL) and leaf mass per area (LMA) than evergreen species. These traits were considered key predictor traits of avoidance and drought tolerance strategies. Deciduous and evergreen species showed a trade-off between drought tolerance and photosynthetic rate, LL was negatively correlated with A mass . Although we have shown clear differences in LMA and LL not observed significant differences in A area and g s , consequently, deciduous species and evergreen species did not find significant differences in WUE i and WUE. Despite substantial variability within the group, all deciduous species fall predominantly in the drought avoidance strategy, while evergreen species display a suite of traits related to drought tolerance.

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“…Gray (brittlebush) is closely associated with seasonal changes of leaf morphology (Cunningham & Strain, 1969;Odening, Strain & Oechel, 1974;Smith & Nobel, 1977, 1978Ehleringer & Mooney, 1978;Ehleringer, 1988). In particular, development of highly reflective leaf pubescence decreases both leaf heat-load and the reliance on transpirational cooling for maintenance of favourable leaf temperatures (Ehleringer & Mooney, 1978).…”

Section: Introductionmentioning

confidence: 99%

Intraspecific variation of leaf pubescence and drought response in Encelia farinosa associated with contrasting desert environments

1997

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SUMMARYTraits associated with leaf energy balance are especially important for desert plants because decoupling leaf and ambient temperatures can be critical for maximizing productivity and survival in these hot, dry regions. Deserts are also one of the most climatically unpredictable and heterogeneous biomes; thus, variation of energy balance characters due either to plasticity or genetic differentiation might also be crucial to the success of desert plant species. In a common garden environment we examined variation in the traits associated with energy balance and productivity in Encelia farinosa A. Gray (brittlebush) plants. Comparing two populations from contrasting rainfall and drought climates, we found that plants from the wetter site (Superior, Arizona) always maintained higher leaf absorptances than plants from the more xeric region (Oatman, Arizona) when at similar water potentials. Superior plants also increased stomatal conductance and photosynthesis in response to mid-spring rainfall, whereas Oatman plants did not. Oatman plants, however, tended to have greater leaf areas and continuous spring growth, which made them larger than Superior plants, yet both populations produced the same number of flower heads. The differences for these traits, and the associations among them, agree with predictions based on the contrasting drought and rainfall environments of these two populations. Our results suggest that the differences might represent alternative suites of characters of selective importance for maximizing carbon gain over the climatically variable range of this widespread species. Furthermore, these differences, detected in common environment conditions, might have a genetic basis, which might contribute to a greater potential for local adaptation in this species.

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The Effect of Decreasing Water Potential on Net CO2 Exchange of Intact Desert Shrubs

Cited by 90 publications

References 21 publications

Photosynthesis in Encelia farinosa Gray in Response to Decreasing Leaf Water Potential

Photosynthesis in Encelia farinosa Gray in Response to Decreasing Leaf Water Potential

Divergências funcionais e estratégias de resistência à seca entre espécies decíduas e sempre verdes tropicais

Intraspecific variation of leaf pubescence and drought response in Encelia farinosa associated with contrasting desert environments

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