Effect Of Leaf Water Potential Research Articles

Defoliation and water leaf potential effects on oenological properties of Merlot (Vitis vinifera L.) grape must

This research was carried out to determine the effects of leaf water potential and defoliation treatments on the oenological properties of grape must. Merlot/41B graft combination grapevines were cultivated in Chateau Kalpak vineyards in Tekirdağ, Şarköy. The trial was carried out for two consecutive years in the vineyard in the vegetation periods of 2019–2020 and 2020–2021. Leaf water potential treatments were S0 (Control = no irrigation), S1 (–0.3/–0.5 MPa), S2 (–0.5/–0.7 MPa) and S3 (<–0.7 MPa) and defoliation treatments were implemented as; Control(C), Full Window(FW), Right Window(RW) and Left Window (LW). As a result, the S2 (–0.5 MPa and –0.7 MPa) stress level resulted in more balanced responses, as seen in the combination of years in terms of both primary and secondary metabolites. The RW defoliation treatment may cause higher primary and secondary metabolite values in all criteria.

Yaprak Alma ve Su Potansiyeli Uygulamalarının Merlot Üzüm Çeşidinde Salkım Özellikleri ve Verime Etkileri

This research was carried out in order to determine the effects of leaf water potential and defoliation applications on the cluster characteristics by using Merlot/41B grafting combination in Chateau Kalpak vineyards in Sarkoy district of Tekirdag province. The trial was carried out in a vineyard for two years in the vegetation period of 2019-2020 and 2020-2021. In the experiment, there were leaf water potential [S0 (Control=no irrigation), S1 (-0.3/-0.5 MPa), S2 (-0.5/-0.7 MPa) and S3(<-0.7) MPa)] and defoliation methods; Control, Full Window, Right Window and Left Window were done respectively. As a result if vigneron’s want; low cluster width, low cluster length, low cluster weight and low number of berry per cluster in Merlot cv. in Sarköy district of Tekirdağ was concluded that Left Window application can be selected. And also S3 application can be preferred when low cluster weight, low cluster volume and low cluster compactness are desired.

Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth

AbstractRemotely sensed microwave observations of vegetation optical depth (VOD) have been widely used for examining vegetation responses to climate. Nevertheless, the relative impacts of phenological changes in leaf biomass and water stress on VOD have not been explicitly disentangled. In particular, determining whether leaf water potential (ψL) affects VOD may allow these data sets as a constraint for plant hydraulic models. Here we test the sensitivity of VOD to variations in ψL and present a conceptual framework that relates VOD to ψL and total biomass including leaves, whose dynamics are measured through leaf area index, and woody components. We used measurements of ψL from three sites across the US—a mixed deciduous forests in Indiana and Missouri and a piñon‐juniper woodland in New Mexico—to validate the conceptual model. The temporal dynamics of X‐band VOD were similar to those of the VOD signal estimated from the new conceptual model with observed ψL (R2 = 0.6–0.8). At the global scale, accounting for a combination of biomass and estimated ψL (based on satellite surface soil moisture data) increased correlations with VOD by ~ 15% and 30% compared to biomass and water potential, respectively. In wetter regions with denser and taller canopy heights, VOD has a higher correlation with leaf area index than with water stress and vice versa in drier regions. Our results demonstrate that variations in both phenology and ψL must be considered to accurately interpret the dynamics of VOD observations for ecological applications.

Plant water potential improves prediction of empirical stomatal models.

Climate change is expected to lead to increases in drought frequency and severity, with deleterious effects on many ecosystems. Stomatal responses to changing environmental conditions form the backbone of all ecosystem models, but are based on empirical relationships and are not well-tested during drought conditions. Here, we use a dataset of 34 woody plant species spanning global forest biomes to examine the effect of leaf water potential on stomatal conductance and test the predictive accuracy of three major stomatal models and a recently proposed model. We find that current leaf-level empirical models have consistent biases of over-prediction of stomatal conductance during dry conditions, particularly at low soil water potentials. Furthermore, the recently proposed stomatal conductance model yields increases in predictive capability compared to current models, and with particular improvement during drought conditions. Our results reveal that including stomatal sensitivity to declining water potential and consequent impairment of plant water transport will improve predictions during drought conditions and show that many biomes contain a diversity of plant stomatal strategies that range from risky to conservative stomatal regulation during water stress. Such improvements in stomatal simulation are greatly needed to help unravel and predict the response of ecosystems to future climate extremes.

Effect of Leaf Water Potential on Internal Humidity and CO2 Dissolution: Reverse Transpiration and Improved Water Use Efficiency under Negative Pressure.

The pull of water from the soil to the leaves causes water in the transpiration stream to be under negative pressure decreasing the water potential below zero. The osmotic concentration also contributes to the decrease in leaf water potential but with much lesser extent. Thus, the surface tension force is approximately balanced by a force induced by negative water potential resulting in concavely curved water-air interfaces in leaves. The lowered water potential causes a reduction in the equilibrium water vapor pressure in internal (sub-stomatal/intercellular) cavities in relation to that over water with the potential of zero, i.e., over the flat surface. The curved surface causes a reduction also in the equilibrium vapor pressure of dissolved CO2, thus enhancing its physical solubility to water. Although the water vapor reduction is acknowledged by plant physiologists its consequences for water vapor exchange at low water potential values have received very little attention. Consequences of the enhanced CO2 solubility to a leaf water-carbon budget have not been considered at all before this study. We use theoretical calculations and modeling to show how the reduction in the vapor pressures affects transpiration and carbon assimilation rates. Our results indicate that the reduction in vapor pressures of water and CO2 could enhance plant water use efficiency up to about 10% at a leaf water potential of −2 MPa, and much more when water potential decreases further. The low water potential allows for a direct stomatal water vapor uptake from the ambient air even at sub-100% relative humidity values. This alone could explain the observed rates of foliar water uptake by e.g., the coastal redwood in the fog belt region of coastal California provided the stomata are sufficiently open. The omission of the reduction in the water vapor pressure causes a bias in the estimates of the stomatal conductance and leaf internal CO2 concentration based on leaf gas exchange measurements. Manufactures of leaf gas exchange measurement systems should incorporate leaf water potentials in measurement set-ups.

A coffee agroecosystem model: I. Growth and development of the coffee plant

This paper is the first of three on the coffee production system consisting of (1) the coffee plant, (2) coffee berry borer (CBB) and (3) the role of CBB parasitoids. A previous simulation model of the coffee plant was developed using data from Brazil where coffee phenology is characterized by distinct seasonal flowering ( Gutierrez et al., 1998). In contrast, flowering in Colombia is continuous with low seasonality. To capture the differences in coffee phenology and growth in the two climatic regions, the Gutierrez et al. (1998) model was modified using new data from Colombia. The modifications to the model include: (1) The effect of solar radiation on floral buds initiation; (2) An age structure population model to track the daily input and development of the floral buds; (3) The effect of leaf water potential on breaking dormancy in flower buds, and hence on the timing and intensity of flowering; (4) The incorporation of both the vegetative and the reproductive demands to predict the photosynthetic rate. (5) The effect of low temperature on photosynthesis and defoliation. Other aspects of the model were re-interpreted and refinements made to generalize its structure for use across coffee varieties and geographic areas. The model, without modification, realistically simulates field data from Brazil and two Colombian locations having different varieties, patterns of rainfall and hence flowering phenology. The model will be used as the base trophic level for incorporating CBB and high tropic levels effects, and for the analysis of management options in the coffee production system.

Effect of leaf Water potential on cold tolerance of Coffea arabica L.

Young coffee plants from cultivar Mundo Novo of Coffea arabica were grown without irrigation for 32 consecutive days, to evaluate the effect of leaf water potential on damage caused by low temperatures, under controlled conditions. A wide range of leaf water potentials were evaluated, from - 0.45MPa (wet soil) at the beginning of the experimental period, to - 4.8MPa (severe leaf wilting) at the end. Results showed that under moderate water stress, there was a higher frequency of undamaged plants and lower frequency of severely damaged plants. These results help explain part of the regional variability observed after a frost and stress the importance of new studies associating cold and drought tolerance in coffee.

Genotypic variation in osmotic adjustment in grain sorghum. I. Development of variation in osmotic adjustment under water-limited conditions

Development of genotypic variation in osmotic adjustment was examined in two glasshouse experiments using two sets of sorghum material. In the first experiment, 47 S2 lines extracted from a randomly mated population were used, whereas in the other, inbred parents and their 15 hybrids were compared. In both experiments, water deficit was induced in two periods, one before anthesis and the other after anthesis for most genotypes. In both experiments osmotic potential at the beginning of the first drying period was similar among genotypes and therefore osmotic potential obtained under water deficit was used for the comparison of osmotic adjustment among genotypes. In the first drying period of both experiments, when stress was milder, about 40% of the variation in osmotic adjustment was accounted for by difference in leaf water potential. When the effect of water potential was removed by covariance analysis, there was significant genotypic variation in osmotic adjustment in the second experiment, but not in the first experiment. On the other hand, in the second drying period, when stress was more severe, the effect of leaf water potential on osmotic adjustment was small. There was significant genotypic variation in osmotic adjustment in both experiments after the water potential effect was removed by covariance analysis. Osmotic adjustment in the second drying period was also negatively correlated with grain sink/source ratio (number of grains/leaf area) in the first set of materials. The comparison of osmotic adjustment among hybrids and their parents showed that, in this particular set of genotypes, the female parents were more important than the male in determining osmotic adjustment of the hybrids. The genotypic variation was associated with performance under water deficit in the field. It is concluded that there is considerable genotypic variation in osmotic adjustment in the genetic material examined. Osmotic adjustment is, however, correlated with water potential and grain sink/source balance, and hence the selection for osmotic adjustment needs to ensure that high value is not due simply to low water potential or small head size.

Net CO2 assimilation of cacao seedlings during periods of plant water deficit

The effect of leaf water potential (Ψ) on net CO2 assimilation rate (A), stomatal conductance (g), transpiration (E) and water-use efficiency (WUE) was measured for three cultivars of cacao (Theobroma cacao L.) seedlings during three recurrent drought cycles. Net assimilation varied greatly at high water potentials, but as Ψ dropped below approximately -0.8 and -1.0 MPa, A was reduced to less than 1.5 μmol CO2 m(-2) s(-1). The relation between g and A was highly significant and conformed to an asymptotic exponential model, with A approaching maximal values at stomatal conductances of 55-65 mmol H2O m(-2) s(-1). Net assimilation varied linearly (r=0.95) with transpiration, and the slope of the A-E relation (WUE) was approximately 3.0 μmol CO2 mmol(-1) H2O throughout the range of stomatal conductances observed. C i was insensitive to water stress, even though both g and A were strongly affected. Under the experimental conditions used here, mesophyll photosynthesis did not appear to control g through changes in C i. As stress intensified within each drying cycle, WUE of nonirrigated seedlings did not decline relative to that of controls even though CO2 and water vapor exchange rates underwent large displacements. The effect of seed source was highly significant for WUE, and the basis for observed differences among genotypes is discussed.

Effect of leaf water potential and air humidity on photosynthetic rate and diffusive conductance in rice plants.

ポットで土耕あるいは水耕栽培した水稲を用いて, 葉の水ポテンシャル(以下Ψlという)と空気湿度とをそれぞれ独立に変えて, 拡散伝導度, 光合成速度に対するΨlと飽差の影響を検討した結果, 次の点を明らかにし得た. (1)拡散伝導度, 光合成速度はΨlが約-1.5barから約-5barに低下するに伴って急激に減少し, それぞれ最大値のほぼ25～40%, 50～60%と著しく小さくなった. (2)Ψlが約-5barよりさらに低下するとΨlの低下に伴う拡散伝導度, 光合成速度の減少程度は小さくなった. (3)拡散伝導度, 光合成速度は, Ψlが高い時にはΨlが等しくても飽差が大きいと減少し, 空気湿度はΨlを介さず拡散伝導度, 光合成速度に直接影響した. (4)この空気湿度の直接の影響はΨlの高い葉身ほど大きく, Ψlが-5bar以下に低下すると認められなくなった. これらの結果と拡散伝導度と光合成速度との関係とから, 光合成速度は, Ψlが高く飽差の影響を著しく受けている時には主として気孔を通じての葉内へのCO2供給速度によって規制され,Ψlが低下し拡散伝導度が小さくなっている時には葉肉細胞における光合成系の活性の低下も加わって減少することが推察された.

The Effect of Leaf Water Potential, Leaf Temperature and Light Intensity on Leaf Diffusion Resistance and the Transpiration of Leaves of Malus sylvestris

AbstractThe relationship between leaf resistance to water vapour diffusion and each of the factors leaf water potential, light intensity and leaf temperature was determined for leaves on seedling apple trees (Malus sylvestris Mill. cv. Granny Smith) in the laboratory. Leaf cuticular resistance was also determined and transpiration was measured on attached leaves for a range of conditions.Leaf resistance was shown to be independent of water potential until potential fell below — 19 bars after which leaf resistance increased rapidly. Exposure of leaves to CO2‐free air extended the range for which resistance was independent of water potential to — 30 bars.The light requirement for minimum leaf resistance was 10 to 20 W m−2 and at light intensities exceeding these, leaf resistance was unaffected by light intensity.Optimum leaf temperature for minimum diffusion resistance was 23 ± 2°C. The rate of change measured in leaf resistance in leaves given a sudden change in leaf temperature increased as the magnitude of the temperature change increased. For a sudden change of 1°C in leaf temperature, diffusion resistance changed at a rate of 0.01 s cm−1 min−1 whilst for a 9°C leaf temperature change, diffusion resistance changed at a rate of 0.1 s cm−1 min−1.Cuticular resistance of these leaves was 125 s cm−1 which is very high compared with resistances for open stomata of 1.5 to 4 s cm−1 and 30 to 35 s cm−1 for stomata closed in the dark.Transpiration was measured in attached apple leaves enclosed in a leaf chamber and exposed to a range of conditions of leaf temperature and ambient water vapour density. Peak transpiration of approximately 5 × 10−6 g cm−2 s−1 occurred at a vapour density gradient from the leaf to the air of 12 to 14 g m−3 after which transpiration declined due presumably to increased stomatal resistance. Leaves in CO2‐free air attained a peak transpiration of 11 × 10−6 g cm−2 s−1 due to lower values of leaf resistance in CO2 free air. Transpiration then declined in these leaves due to development of an internal leaf resistance (of up to 2 s cm−1). The internal resistance was masked in leaves at normal CO2 concentrations by the increase in stomatal resistance.

An ecophysiological approach to crop losses, exemplified in the system wheat, leaf rust and glume blotch

Effects of leaf rust (Puccinia recondita Rob. ex Desm. f.sp.triticina Eriks.) infection of spring wheat (Triticum aestivum L.) plants ‘Kolibri’ on transpiration rate and leaf-water potential were studied during growth in a climate chamber at various soil-water potentials. The water potentials ranged from −210 J.kg−1 to −1025 J.kg−1. Rust infection has been found to increase the transpiration rate. The magnitude and duration of the increase depended on soil-water potential and the time (growth stage) of inoculation. The transpiration rate of uninfected heads was affected by rust infection of the leaves, also depending on soil-water potential and infection time. Overall resistance of the plants to water flow was determined; sudden changes in resistance due to rust infection concur with high crop losses due to abortion of kernels. Leaf-water potentials were calculated and found to vary in uninfected plants from −1740 J.kg−1 at the lowest soil-water potential to −580 J.kg−1 when water was plentiful. At high soil-water potential, the leaf-water potential of rusted plants was lower than that of uninfected plants, but this was not so at low soil-water potentials. The effects of leaf-water potential on rust growth and water flow through leaves and heads are discussed. Suggestions about the application of the results to breeding for tolerance (= resistance to loss) and, eventually, to prevention of loss by rust in semi-arid areas are given.

Water Potential in Red Pine: Soil Moisture, Evapotranspiration, Crown Position

Diurnal patterns in leaf water potential were examined on eight red pine trees throughout one summer in northern Minnesota. The daily high in leaf water potential was plotted against total soil moisture to produce a soil—moisture release curve characterizing the plant—soil—atmosphere system. Diurnal patterns in leaf water potential at various soil moistures were compared. Also compared were patterns in leaf water potential under high and low evaporational demand and constant soil moisture. Results were generally consistent with previously constructed models. Very little variation in leaf water potential was observed among whorls or needle ages. Laboratory studies of the effects of leaf water potential when synthesized with data from the forest on occurrence of leaf water potentials suggest that growth was limited by water deficit every day of the 1969 summer.