Physical Aspects of the Internal Water Relations of Plant Leaves

Gardner, W. R.; Ehlig, C. F.

doi:10.1104/pp.40.4.705

Cited by 111 publications

(53 citation statements)

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“…Leaf thickness has also been hypothesized to be closely related to water potential. According to Gardner and Ehling (1965), high temperature lowers the leaf water potential of cabbage thereby reducing leaf thickness, which in turn makes heading more difficult. This results in loose heads and subsequently lower cabbage yields and quality observed under high temperatures.…”

Section: Effects Of Agronets On Yields and Quality Of Cabbagementioning

confidence: 99%

Enhancing Cabbage (Brassica oleraceae Var capitata) Yields and Quality Through Microclimate Modification and Physiological Improvement Using Agronet Covers

Muleke

Saidi

Itulya

et al. 2014

SAR

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Adverse environmental conditions have contributed to perpetual poor cabbage (Brassica oleraceae var. capitata) yields in sub-Saharan Africa. Elsewhere, net covers have been reported to provide a low-cost technology with the potential of modifying the microclimate around a crop for better performance. Two experiments were therefore conducted over a span of two seasons to determine the effects of agronet covers on microclimate modification and subsequent cabbage yield and quality. The treatments comprised cabbage plants grown under either fine mesh (0.4 mm pore diameter) or large mesh (0.9 mm pore diameter) agronet covers maintained permanently closed, or opened thrice weekly from 9 am to 3 pm and a control treatment where cabbage was grown in the open field. Net covering generally modified the microclimate by raising temperatures, relative humidity and volumetric water content but lowering photosynthetic active radiation and diurnal temperature range compared to control. The use of agronet covers resulted in better cabbage performance. The large mesh (0.9 mm) enhanced leaf stomatal conductance and chlorophyll content, and improved fresh and dry weight as well as head quality. Results of this study present the use of agronet covers as a potentially effective technology for use by small-scale farmers in protected cabbage culture in sub-Saharan Africa.

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Section: Effects Of Agronets On Yields and Quality Of Cabbagementioning

confidence: 99%

Enhancing Cabbage (Brassica oleraceae Var capitata) Yields and Quality Through Microclimate Modification and Physiological Improvement Using Agronet Covers

Muleke

Saidi

Itulya

et al. 2014

SAR

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“…Leaves shrink in their area (Bogue, 1892;Gardner and Ehlig, 1965;Jones, 1973;Tang and Boyer, 2007;Blonder et al, 2012) and, considered in relative terms, even more strongly in their thickness (Fig. 1;Meidner, 1952;Gardner and Ehlig, 1965;Downey and Miller, 1971;Syvertsen and Levy, 1982;Saini and Rathore, 1983;Burquez, 1987;McBurney, 1992;Sancho-Knapik et al, 2010. Leaves fluctuate in thickness daily and seasonally according to transpiration (Kadoya et al, 1975;Tyree and Cameron, 1977;Fensom and Donald, 1982;Rozema et al, 1987;Ogaya and Peñuelas, 2006;Seelig et al, 2012).…”

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Leaf Shrinkage with Dehydration: Coordination with Hydraulic Vulnerability and Drought Tolerance

et al. 2013

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Leaf shrinkage with dehydration has attracted attention for over 100 years, especially as it becomes visibly extreme during drought. However, little has been known of its correlation with physiology. Computer simulations of the leaf hydraulic system showed that a reduction of hydraulic conductance of the mesophyll pathways outside the xylem would cause a strong decline of leaf hydraulic conductance (K leaf ). For 14 diverse species, we tested the hypothesis that shrinkage during dehydration (i.e. in whole leaf, cell and airspace thickness, and leaf area) is associated with reduction in K leaf at declining leaf water potential (C leaf ). We tested hypotheses for the linkage of leaf shrinkage with structural and physiological water relations parameters, including modulus of elasticity, osmotic pressure at full turgor, turgor loss point (TLP), and cuticular conductance. Species originating from moist habitats showed substantial shrinkage during dehydration before reaching TLP, in contrast with species originating from dry habitats. Across species, the decline of K leaf with mild dehydration (i.e. the initial slope of the K leaf versus C leaf curve) correlated with the decline of leaf thickness (the slope of the leaf thickness versus C leaf curve), as expected based on predictions from computer simulations. Leaf thickness shrinkage before TLP correlated across species with lower modulus of elasticity and with less negative osmotic pressure at full turgor, as did leaf area shrinkage between full turgor and oven desiccation. These findings point to a role for leaf shrinkage in hydraulic decline during mild dehydration, with potential impacts on drought adaptation for cells and leaves, influencing plant ecological distributions.

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“…Matric potentials have been postulated for plant leaves (6,16,17) but they have not been measured. In this report, I show that plant leaves have significant matric potentials and present evidence that the matric potentials which are observed are associate(d mainly with the cell walls.…”

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Matric Potentials of Leaves

Boyer

1967

Plant Physiol.

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SummDlleary. A pressure chamber was used to measture matric potentials of frozen and thawed leaves. Significant matric potentials were demonstrated in sunflower (Helianthus annuus L.), yew (Taxus cuspidata Sieb. and Zucc.), and rhododendron (Rhododendron roseum Rehd.). Matric potentials were particuilarly negative in rhododendron and were correlated with the amount of cell wall present and with the voluime of water outside the leaf protoplasts at comparable matric potentials. It was concluded that matric forces in leaves are associated mainly with cell walls, at least within the physiological range of water contents. Calculations indicated that the water potential of the solution in the cell wall could be estimated for living tissue from the suim of matric and osmotic potentials acting on water outside the protoplasts.The availability of water to soil-grown plants is determined in largest part by the interaction of water with the surfaces of soil particles and by the effects of soil solutes. It has been convenient to group the surface forces, tusually adsorptive and capillary forces, in a single term, matric potential (2,9,15,16 PLANT PHYSIOLOGY potential has uistually been sttdiedl in systems with -arying water contents (10, 1t) and this is the approach adopted here. Materials and MethodsThree species having leaves and stems of widely different anatomy were chosen for sttudy: suinflower (Heliant has annuas L.), yew (Taxuts cutspidata Sieb. and Zucc.), and rhododenidroin (Rhododendron roseumn Rehd.). Two year old yew and rhododendron were grown in soil in the greenhouise. Sulnflower was groxvn from seed in soil in a controlled environment room (temp, 30-31 (lay and 27-28' night; relative humidity, 45-55 %; light, 2500 ft-c).Matric potentials were measured with a pressture chamber (12,13) in leafy shoots 20 to 30 cm long (rhododendroni and yew) and leaves (suinflower) that hadl been frozen at -20°and slowly thawed. The chamber was slightly modified by bubbling the incoming nitrogen gas through water in the bottom of the chamber to prevent drying of the tisstle. A baffle prevented the water from splashing onl the tissue.Matric potentials were (letermine(d as a ftunction of the water content of the plaint tissue by placiing a frozen and thawed plaint sample in the pressuire chamber with the cuit stem protrutding through the top of the chamber. Several aliquiots of cell sap were expressed by raising the pressuire aroulndl the plant sample. After each aliquiot was removed, the balancing pressure was (letermined and( represeinted the matric potential at that water content. Following the measturement of matric potentials, the total water in the sample was (letermined by Ir-ing at 100°and adding the water loss (dtiring (Irving to the volume of cell sap in aliqulots collecte(d while the sample had been subjected to presstire.The a-erage cell wall volume of the leaf mesophyll cells was determined after stainiing fresh leaf cross sections with Schiff reagenit by the PAS method (8). The average volume of the protoplast a...

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Physical Aspects of the Internal Water Relations of Plant Leaves

Cited by 111 publications

References 2 publications

Enhancing Cabbage (Brassica oleraceae Var capitata) Yields and Quality Through Microclimate Modification and Physiological Improvement Using Agronet Covers

Enhancing Cabbage (Brassica oleraceae Var capitata) Yields and Quality Through Microclimate Modification and Physiological Improvement Using Agronet Covers

Leaf Shrinkage with Dehydration: Coordination with Hydraulic Vulnerability and Drought Tolerance

Matric Potentials of Leaves

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