Visual assessment of total plant relative water content, with the aid of photographic standards, as a guide to scheduling irrigation

1974 ◽  
Vol 14 (66) ◽  
pp. 76
Author(s):  
GJ Luke
Keyword(s):  
Water Stress ◽  
Water Status ◽  
Visual Assessment ◽  
Whole Plant ◽  
Accurate Indication ◽  
Relative Water ◽  
Total Plant ◽  
Scheduling Irrigation ◽  
Maize Plants ◽  
Water Contents

The relative water contents (RWC) of the top and bottom leaves of maize plants were measured. The RWC of the top leaf was higher than that of the bottom leaf when the plant was under water stress. Photographic standards based on the RWC of the whole plant were developed and tested against plants in the field. The results showed that the standards give an accurate indication of the plant's water status. Standards based on the upper leaf only would result in irrigations too infrequent to prevent severe restrictions to photosynthesis.

Water stress affects the productivity, growth components, competitiveness and water relations of phalaris and white clover growing in a mixed pasture

1992 ◽  
Vol 43 (3) ◽  
pp. 659 ◽  
Author(s):  
L Guobin ◽  
DR Kemp ◽  
GB Liu
Keyword(s):  
Water Stress ◽  
Soil Water ◽  
White Clover ◽  
Leaf Growth ◽  
Leaf Water ◽  
Water Potentials ◽  
Relative Water ◽  
Dry Conditions ◽  
Leaf Appearance ◽  
Water Contents

The effect of water stress during summer and recovery after rain on herbage accumulation, leaf growth components, stomatal conductance and leaf water relations of white clover (Trifolium repens cv. Haifa) and phalaris (Phalaris aquatica cv. Australian Commercial) was studied in an established mixed pasture under dryland (dry) or irrigated (wet) conditions. Soil water deficits under dry conditions reached 150 mm and soil water potentials in the top 20 cm declined to nearly -2 MPa after 50 days of dry weather. Water stress severely restricted growth of both species but then after rain fell, white clover growth rates exceeded those of phalaris. Under irrigation, white clover produced twice the herbage mass of phalaris but under dry conditions herbage production was similar from both species. Leaf appearance rates per tiller or stolon were slightly higher for white clover than phalaris but were reduced by 20% under water stress in both species. Leaf or petiole extension rates were more sensitive to water stress than leaf appearance rates and declined by 75% in phalaris and 90% in white clover. The ratio of leaf or petiole extension rates on dry/wet treatments was similar for both species in relation to leaf relative water contents, but in relation to leaf water potentials phalaris maintained higher leaf growth rates. Phalaris maintained a higher leaf relative water content in relation to leaf water potentials than did white clover and also maintained higher leaf water potentials in relation to the soil water potential in the top 20 cm. Stomata1 conductances for both species declined by 80-90% with increasing water stress, and both species showed similar stomatal responses to bulk leaf water potentials and leaf relative water contents. It is suggested that the poorer performance of white clover under water stress may be due principally to a shallower root system than phalaris and not due to any underlying major physiological differences. The white clover cultivar used in this study came from the mediterranean region and showed some different responses to water stress than previously published evidence on white clover. This suggests genetic variation in responses to water stress may exist within white clover. To maintain white clover in a pasture under dry conditions it is suggested that grazing practices aim to retain a high proportion of growing points.

scholarly journals How water availability influences morphological and biomechanical properties in the one-leaf plant Monophyllaea horsfieldii

2018 ◽  
Vol 5 (1) ◽  
pp. 171076 ◽  
Author(s):  
Tim Kampowski ◽  
Max David Mylo ◽  
Simon Poppinga ◽  
Thomas Speck
Keyword(s):  
Water Stress ◽  
Imaging Techniques ◽  
Water Status ◽  
Natural Habitat ◽  
Turgor Pressure ◽  
Biomechanical Properties ◽  
Cell Form ◽  
Postural Changes ◽  
The One ◽  
Water Contents

In its natural habitat, the one-leaf plant Monophyllaea horsfieldii (Gesneriaceae) shows striking postural changes and dramatic loss of stability in response to intermittently occurring droughts. As the morphological, anatomical and biomechanical bases of these alterations are as yet unclear, we examined the influence of varying water contents on M. horsfieldii by conducting dehydration–rehydration experiments together with various imaging techniques as well as quantitative bending and turgor pressure measurements. As long as only moderate water stress was applied, gradual reductions in hypocotyl diameters and structural bending moduli during dehydration were almost always rapidly recovered in acropetal direction upon rehydration. On an anatomical scale, M. horsfieldii hypocotyls revealed substantial water stress-induced alterations in parenchymatous tissues, whereas the cell form and structure of epidermal and vascular tissues hardly changed. In summary, the functional morphology and biomechanics of M. horsfieldii hypocotyls directly correlated with water status alterations and associated physiological parameters (i.e. turgor pressure). Moreover, M. horsfieldii showed only little passive structural–functional adaptations to dehydration in comparison with poikilohydrous Ramonda myconi .

scholarly journals Capillary Mats Alter the Water Content in Medium during Mist Propagation of Dendranthema

HortScience ◽  
2004 ◽  
Vol 39 (3) ◽  
pp. 584-587 ◽  
Author(s):  
R.L. Geneve ◽  
S.T. Kester ◽  
J.W. Buxton
Keyword(s):  
Water Content ◽  
Water Table ◽  
Relative Water Content ◽  
Water Status ◽  
Internal Water ◽  
Relative Water ◽  
Reduced Water ◽  
Water Contents

A capillary mat-mist system was developed to provide near constant media water contents at differing quantities of mist. Media water contents were reduced by increasing the capillary mat height above a constant water table maintained at bench level. Increased tensions from 0 to 10 cm above the water table reduced water content in Oasis, rockwool, and peat-perlite by 35.4%, 27.6%, and 17.4%, respectively. There was no difference in water content for each medium when the mist quantity ranged between 600 and 1800 mL·m-2·h-1, except when the capillary mat was at 9 cm above the water table and mist volume was 300 mL·m-2·h-1. Chrysanthemum cuttings rooted best when water content was highest regardless of media. Using the peat-perlite medium, water content had the greatest impact on rooting when the mist volume was low (600 mL·m-2·h-1). Relative water content of cuttings was lowest during the first 5 days of sticking and both reduced media water content and mist quantity resulted in the lowest internal water status for the cuttings.

scholarly journals EFEITOS DO DÉFICIT HÍDRICO EM PARÂMETROS FISIOLÓGICOS DE FOLHAS DE SORGO (Sorghum bicolor, L.)

Irriga ◽  
1998 ◽  
Vol 3 (3) ◽  
pp. 81-88
Author(s):  
Carlos Augusto Lima Porto ◽  
Antonio Evaldo Klar ◽  
José Vicente Vasconcelos
Keyword(s):  
Water Stress ◽  
Sorghum Bicolor ◽  
Water Potential ◽  
Water Content ◽  
Relative Water Content ◽  
Water Status ◽  
Soil Water Potential ◽  
Relative Water ◽  
Conductivity Water ◽  
Sorghum Bicolor L

EFEITOS DO DÉFICIT HÍDRICO EM PARÂMETROS FISIOLÓGICOS DE FOLHAS DE SORGO (Sorghum bicolor, L.)  Carlos Augusto Lima PortoAntonio Evaldo Klar(2)José Vicente VasconcelosDepartamento de Engenharia Rural – Faculdade de Ciências Agronômicas – UNESPFone: (014) 821-3883  Fax: (014) 821-343818603-97’ – Botucatu - SP  1 RESUMO O experimento foi conduzido em casa de vegetação no Departamento de Engenharia Rural da Faculdade de Ciências Agronômicas - UNESP/Botucatu, SP, com delineamento experimental inteiramente casualizado, com 12 repetições. A cultura do sorgo (Sorghum bicolor, L.) foi plantada em vasos que continham 8,0 kg de solo (base em peso de solo seco), pertencente ao grande grupo Terra Roxa Estruturada para os dois tratamentos: a) plantas submetidas a défices  hídricos, sendo irrigadas quando o potencial de água no solo chegava a -1,5 MPa, elevando-o às imediações de -0,01 MPa), e b) plantas irrigadas constantemente por capilaridade. Todas as plantas foram irrigadas aos 55 dias após a emergência e os parâmetros avaliados foram: condutância estomática, potencial de água e teor relativo de água nas folhas mais novas totalmente expandidas, com determinações diárias entre as onze e treze horas, até que o potencial de água no solo atingisse valores em torno de -1,5 MPa. Da análise geral dos dados obtidos, pode-se inferir que a variação no status de água na folha observado através do potencial e do teor relativo de água nas folhas pode ser utilizado para indicar o momento de irrigar; ainda estas medições podem ser indicativas das plantas ou cultivares de sorgo que se mostram mais tolerantes à seca e que o mecanismo de adaptação é o  “avoidance”. UNITERMOS: Condutividade estomática, potencial de água na folha, teor relativo de água na folha,  tolerância à seca.  PORTO, C. A . L.., KLAR, A. E. , VASCONCELLOS, V. J.  Water deficit on physiological parameters of soybean  leaves (Sorghum bicolor L).  2 ABSTRACT A study was carried out at Agricultural Engineering Department, UNESP, Botucatu - SP, with a sorghum crop (Sorghum bicolor, L.) in order to physiologically evaluate the crop response to drought. A completely random design with twelve replications were used. Pots with 8 kg of a medium texture soil (dry weight basis) were used in order to test the influence of the two treatments: a) plants being submitted to a water stress, where irrigation were done when the water potential in the soil (s) were -1,5 MPa, raising it to about -0,01 MPa, and b) plants being always irrigated by capillary. The parameters evaluated were water vapor stomata conductivity, water potential  and relative water content in the leaves.  All plants were irrigated at 55 days after emergency, with daily determinations from eleven AM to thirteen PM, until soil water potential reaches around -1,5MPa. From the general data analysis, it can be inferred that there was a significant variation in the water status in the leaves by determinations of water potential and relative water content in the leaves, indicating that the method may be used to indicate the moment of irrigation and the plants and cultivars more tolerant to drought.  Sorghum plants showed adaptation to water stress under avoidance mechanism. KEYWORDS: Stomata conductivity, water potential in the leaves, relative water content, drought tolerance.

scholarly journals Osmotic and Turgor Adjustment in Rosa Foliage Drought-stressed under Varying Irradiance

1990 ◽  
Vol 115 (4) ◽  
pp. 661-667 ◽  
Author(s):  
Robert M. Augé ◽  
Ann J.W. Stodola ◽  
Brian D. Pennell
Keyword(s):  
Soil Moisture ◽  
Elastic Modulus ◽  
Water Stress ◽  
Relative Water Content ◽  
The Other ◽  
Ambient Light ◽  
Moisture Treatment ◽  
Relative Water ◽  
Osmotic Potentials ◽  
Water Contents

The influence of irradiance and drought on osmotic and turgor adjustment was examined in leaves of rose (Rosa hybrida L. `Samantha'). Plants cultured under full ambient light in the greenhouse were placed in shade chambers and, after 2 weeks of acclimation, exposed to drought for 21 days. Treatments consisted of a water stress factor (well-watered and drought-stressed) and an irradiance factor (100%, 70%, and 30% of ambient irradiance). Pressure-volume analyses of leaves indicated that osmotic potentials at full turgor were decreased 0.42, 0.36, and 0.23 MPa by drought in the 100%, 70%, and 30% irradiance treatments, respectively. Plants stressed under 100% and 70% irradiance exhibited similar osmotic adjustments. Plants under 30% irradiance had higher osmotic potentials at full turgor under well-watered conditions than plants in the other two irradiance treatments and showed only 55% as much adjustment to drought. In each irradiance treatment, drought induced an increase in elastic modulus and a decrease in relative water content at zero turgor. Turgor pressures were higher across a range of relative water contents in plants in the two higher irradiance treatments under both soil moisture treatments. Turgor also was higher at any particular water potential at 100% and 70% irradiance than 30% irradiance, within each soil moisture treatment. Heavy, but not mild, shading inhibited osmotic and turgor adjustments in leaves during drought.

scholarly journals Rapid and Efficient Determination of Relative Water Contents of Crop Leaves Using Electrical Impedance Spectroscopy in Vegetative Growth Stage

2020 ◽  
Vol 12 (11) ◽  
pp. 1753
Author(s):  
Rinku Basak ◽  
Khan A. Wahid ◽  
Anh Dinh ◽  
Raju Soolanayakanahally ◽  
Reza Fotouhi ◽  
...  
Keyword(s):  
Water Stress ◽  
Impedance Spectroscopy ◽  
Electrical Impedance ◽  
Growth Stage ◽  
Leaf Water ◽  
Electrical Impedance Spectroscopy ◽  
Crop Water ◽  
Relative Water ◽  
Water Contents ◽  
Crop Water Stress

Crop water stress is a deficiency in plants in water supply when the transpiration rate becomes higher than the water absorption capacity. The stress may be detected by a reduction in soil water content, or by the change in physiological properties of the crop. The leaf water content (LWC) is commonly used to assess the water status of plants, which is one of the indicators of crop water stress. In this work, the leaf relative water contents of four different crops: canola, wheat, soybeans, and corn—all in vegetative growth stage—were determined by a noninvasive tool called, electrical impedance spectroscopy (EIS). Using a frequency range of 5–15 kHz, a strong correlation between leaf water contents and leaf impedances was obtained using multiple linear regression. The trained dataset was validated by analysis of variance tests. Regression results were obtained using the least square method. The optimized regression model coefficients for different crops were proposed by selecting features using the wrapper backward elimination method. Multi-collinearity among the features was considered and individual T-tests were made in the feature selection. A maximum correlation coefficient (R) of 0.99 was obtained for canola compared to the other crops; the corresponding coefficient of determination (R2) of 0.98, an adjusted R2 of 0.93, and root mean square error (rmse) of 0.30% were obtained for 36 features. Therefore, the results show that the proposed technique using EIS can be used to develop a low-cost and effective tool for determining the leaf water contents rapidly and efficiently in multiple crops.

scholarly journals Effects of atmospheric and soil water status on photosynthesis and growth in tomato

2018 ◽  
Vol 64 (No. 1) ◽  
pp. 13-19 ◽  
Author(s):  
Du Qingjie ◽  
Zhang Dalong ◽  
Jiao Xiaocong ◽  
Song Xiaoming ◽  
Li Jianming
Keyword(s):  
Water Stress ◽  
Water Status ◽  
Vapour Pressure Deficit ◽  
Plant Water Status ◽  
Plant Water ◽  
Stomatal Development ◽  
Stomatal Limitation ◽  
Tomato Seedlings ◽  
Inhibition Of Growth ◽  
Whole Plant

The responses of tomato seedlings to different vapour pressure deficit (VPD) under low soil moisture were studied. Plants were grown in greenhouses with low and high VPD, under both well-watered and water stress conditions. Low VPD was effectively maintained below 1.5 kPa with a micro-fog system. Under well-watered conditions, low VPD resulted in reduced transpiration, but this did not affect plant water status or growth. Water stress induced leaf dehydration and inhibition of growth, but the adverse effects were significantly alleviated by a decrease in VPD. Under water stress, no difference in transpiration was observed between plants with or without the VPD regulation, but the whole-plant hydraulic conductance was higher under low VPD. Low VPD increased stomatal conductance in drought-stressed plants because it promoted stomatal development and increased stomatal aperture. Thus, stomatal limitation to photosynthesis was reduced by low VPD under water stress. The reduction in plant growth induced by water stress was moderated by low VPD, partially due to higher photosynthetic rate. These results suggest that decreasing VPD improves plant water status, which ultimately enhances photosynthesis and growth under water stress.

scholarly journals Influence of Water Stress on Grapevines Growing in the Field: From Leaf to Whole-Plant Response

1993 ◽  
Vol 20 (2) ◽  
pp. 143 ◽  
Author(s):  
T Winkel ◽  
S Rambal
Keyword(s):  
Water Stress ◽  
Leaf Area ◽  
Water Status ◽  
Stomatal Closure ◽  
Indirect Evidence ◽  
Hydraulic Conductance ◽  
Water Vapour Pressure ◽  
Vitis Vinifera L ◽  
Plant Water ◽  
Whole Plant

A comparative study of soil-plant water relations was conducted on three grapevine cultivars (Vitis vinifera L. cvv. carignane, merlot, shiraz) to investigate their adjustment to short-term and long-term water stress under field conditions. Adjustment was a function of the relative stability of the internal plant water status on diurnal and seasonal scales. On a diurnal scale, stomatal closure in response to water vapour pressure directly contributed to this stability. Indirect evidence suggested an influence of the soil water status on the diurnal stomatal activity. On a seasonal scale, sufficient leaf hydration required high whole-plant hydraulic conductance. This was achieved by either daily stomatal regulation or limitation of leaf area. Physiological adjustment to water stress through stomatal control was well developed in cv. carignane, which originated in a Mediterranean environment. However, cv. shiraz, which was of mesic origin, apparently adjusted to water stress by reducing leaf area. Our study demonstrates the utility of integrating data on stomatal conductance, leaf water potential and whole-plant hydraulic conductance to interpret whole plant adaptation to water stress, and elucidates two mechanisms by which genotypes differentially acclimate to water stress.

EXPERIMENTAL ASSESSMENT OF THE IMPACT OF DEFOLIATION ON GROWTH AND PRODUCTION OF WATER-STRESSED MAIZE AND COTTON PLANTS

2004 ◽  
Vol 40 (2) ◽  
pp. 189-199 ◽  
Author(s):  
Z. YANG ◽  
D. J. MIDMORE
Keyword(s):  
Water Stress ◽  
Management Practice ◽  
Water Status ◽  
Relative Yield ◽  
Cotton Plants ◽  
Maize Plants ◽  
Effect On Yield ◽  
The Impact ◽  
Reduced Water ◽  
Yield Decrease

In this study, different levels of defoliation were imposed on a determinate species (maize) and a relatively indeterminate species (cotton). The aim was to quantify the effects of defoliation on plant growth and production, under either optimum or water-stressed conditions. Under well-watered conditions, 33% defoliation twice (conducted 28 and 35 days after emergence) resulted in a 16% reduction in grain yield of maize while 67% defoliation once (conducted 28 days after emergence) had no significant effect on yield. Under water stress, the grain yields of maize plants with 33% (twice) and 67% defoliation were 13.5% and 25% greater than that of non-defoliated control plants, respectively. For cotton, the reproductive yields (seed and lint) with 33% and 67% defoliation (conducted 43 days after emergence) were reduced, under well-watered conditions, by 28% and 37% of that of the non-defoliated control, respectively. Defoliated cotton plants lost less fruiting forms (squares and young bolls) than non-defoliated plants during water stress. Therefore, under water stress the harvestable product of cotton plants with 67% defoliation was double that of non-defoliated control plants. In non-defoliated cotton plants, a second flush of flowering after release from water-stress permitted further compensatory fruit set and boll harvest. Defoliated plants did not show such levels of compensation. Defoliation significantly reduced water use by maize and cotton. The relative yield advantage of defoliated plants under water-stress conditions can be attributed to defoliation-induced improvement in water status as reflected in measures of photosynthetic rate and stomatal conductance. Under anticipated drought stress, defoliation could be an important management practice to reduce drought-induced yield decrease, but this needs to be tested under field conditions.

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