Growth, stomatal resistance, and transpiration of Aloe vera under different soil water potentials

2007 ◽  
Vol 25 (2) ◽  
pp. 123-128 ◽  
Author(s):  
R. Rodríguez-García ◽  
D. Jasso de Rodríguez ◽  
J.A. Gil-Marín ◽  
J.L. Angulo-Sánchez ◽  
R.H. Lira-Saldivar
Keyword(s):  
Soil Water ◽  
Aloe Vera ◽  
Stomatal Resistance ◽  
Water Potentials

Transpiration and leaf water potentials of wheat in relation to changing soil water potential

1977 ◽  
Vol 28 (3) ◽  
pp. 355 ◽  
Author(s):  
KA Seaton ◽  
JJ Landsberg ◽  
RH Sedgley
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Transpiration Rate ◽  
Water Conservation ◽  
Root Zone ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Stomatal Resistance ◽  
Leaf Water ◽  
Water Potentials

Changes in the transpiration rate of wheat in drying soils were followed in experiments in which plants were grown in two small weighable lysimeters in a glasshouse. Hourly measurements of soil water potential (Ψs) were made at three depths in each lysimeter. The water potential of flag leaves was measured with a pressure chamber, and stomatal resistance with a pressure drop porometer. Data on root densities and distribution were also obtained. Transpiration rates fell below estimated potential levels when the average value of Ψs in the root zone was reduced to –1 to –5 bars, depending on soil storage, root distribution and potential transpiration rate. From this point Ψs fell rapidly in the surface layers, more slowly at depth. It was found that accurate calculations of daily water uptake could be made from changes in soil water content. The minimum value of leaf water potential (�1 )attained each day declined progressively through the drying cycle, but there was evidence that stomatal resistance (rs) is not uniquely related to Ψ1; initial stomatal closure occurred at Ψ1, values which decreased from –11 to –25 bars as drying progressed. This adaptive mechanism is related to changes in osmotic potential of the leaves. Whole plant resistances (Rp), derived from leaf water potentials and fluxes through individual stems, increased as stem populations increased. In the high population lysimeter Rp decreased from 300 to 100 bar sec mm-3 as canopy transpiration rates increased from 1.5 to 4.5 x 10-4 mm sec-1. In the low population lysimeter Rp decreased from 70 to 30 bar sec mm-3 as transpiration increased from about 2.2 to 4.5 x 10-4 mm sec-1. The higher resistances appear to confer significant advantages in terms of water conservation and adaptation to drought.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

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 ANÁLISE DE CRESCIMENTO EM CLONES DE EUCALIPTO SUBMETIDOS A ESTRESSE HÍDRICO

Irriga ◽  
2010 ◽  
Vol 15 (1) ◽  
pp. 98-110 ◽  
Author(s):  
Maria Renata Rocha Pereira ◽  
Guilherme Sasso Ferreira Souza ◽  
Andreia Cristina Peres Rodrigues ◽  
Andre Luiz Melhorança Filho ◽  
Antonio Evaldo Klar
Keyword(s):  
Soil Water ◽  
Leaf Area ◽  
Genetic Material ◽  
Area Index ◽  
Growth Ratio ◽  
Relative Growth ◽  
Water Potentials ◽  
Absolute Growth ◽  
Hydric Stress ◽  
East West

O estudo objetivou avaliar o desempenho de genótipos de plantas de Eucalyptus urograndis (clone 105 e 433) em relação à tolerância à seca, considerando a análise de crescimento das plantas. Para tanto, plantas foram cultivadas em vasos de 8 litros em casa de vegetação. O delineamento foi em inteiramente casualizado, com quatro tratamentos contendo desesseis repetições. O manejo hídrico foi estabelecido com base em dois potenciais mínimos de água (Ψ): -0,03 e -1,5 MPa, através da pesagem diária dos vasos. O desenvolvimento das plantas foi avaliado em coletas a intervalos de 15 dias, iniciando no momento de plantio da muda no vaso até os 60 dias após plantio. Considerando-se o acúmulo de matéria seca total (MS) e o índice de área foliar da planta (IAF) como base para a determinação dos seguintes índices fisiológicos: razão de área foliar (RAF), taxa assimilatória líquida (TAL), área foliar específica (AFE), taxa de crescimento relativo (TCR) e taxa de crescimento absoluto (TCA). Nas condições do experimento, o clone 105 apresentou menor sensibilidade ao déficit hídrico, o que o qualifica como material genético promissor para ambientes sujeitos a estiagem prolongada. Já em condições em que não há restrição hídrica, os dois clones tiveram comportamento semelhantes.   UNITERMOS: Eucaliptus urograndis, índices fisiológicos, potenciais hídricos do solo     PEREIRA, M. R. R.; SOUZA, G. S. F. de; RODRIGUES, A. C. P.; MELHORANÇA FILHO, A. L.; KLAR, A. E. GROWTH ANALYSIS OF CLONE EUCALIPTUS UNDER HYDRIC STRESS     2 ABSTRACT   The aim of this study was to evaluate Eucaliptus grandis genotypes (Clones 105 and 433) in relation to drought  tolerance, through growth plant analysis.  Black PVC pots with 10 liter volume were used for cultivate plants in polyethilene greenhouse oriented east/west. Completely randonmized design with four treatments was used: two clones and two minimum soil water  potentials ( - 0.03 and -1,5 MPa) and sixteen replicates.  Pots were weighed daily in order to evaluate water content and characteristic soli water curve was determined. Plant development was obtained each 15 days from planting until 60 days  through  total dry matter (DM), leaf area index (LAI),  leaf area ratio (LAR), net assimilative ratio (NAR), specific leaf area (SLA), relative growth ratio (RGR) and absolute growth ratio (AGR). Results showed that clone 105 presented less sensibility to water deficit, which qualify it as genetic material for use under dry soil conditons.  On the other hand, both clones had similar behavior with no water restrictions.   KEYWORDS: Eucaliptus grandis, soil water potentials, morphologic measurements.  

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