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Jingjin Yu, Mengxian Liu, Zhimin Yang, and Bingru Huang

process. Osmotic adjustment was determined by Ψ S of leaf sap at full turgor. Leaf samples were collected and soaked in deionized water for 4 h, blotted dry, placed into microcentrifuge tubes, frozen in liquid nitrogen, and stored at −20 °C until further

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Sanalkumar Krishnan and Emily B. Merewitz

control plants under drought stress. Fig. 4. Effect of polyamine (PA) application (spermine and spermidine) on osmotic adjustment (MPa) of creeping bentgrass ‘Penn-G2’ under well-watered or drought conditions at 3 and 10 d. The data presented here are from

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Mayashree Chinsamy, Manoj G. Kulkarni, and Johannes Van Staden

adjustment by the accumulation of solutes is necessary to lower the risk of osmotic and oxidative stress. Water-stressed tomato seedlings were previously shown to have increased concentrations of compatible solutes such as sucrose, glucose, fructose, and

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Tessa M. Mills, Jianming Li, and M. Hossein Behboudian

of osmotic adjustment that has been reported for A. deliciosa ( Chartzoulakis et al., 1997 ) when water deficit was imposed for longer than 10 d. No literature reports for A. chinensis are available for comparison and confirmation of osmotic

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Mohamad Hossein Sheikh Mohamadi, Nematollah Etemadi, Ali Nikbakht, and Mohammad Pessarakli

evaluated. For instance, Bian et al. (2009) reported that TE application effectively influenced turf growth during drought stress by reducing water use and improving osmotic adjustment. Also, TE has been shown to increase salinity tolerance of bermudagrass

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Eric Young, J. Mark Hand, and Steven C. Wiest

Abstract

Peach [Prunus persica, (L.) Batsch] seedling growing in irrigated soil showed strong diurnal variations in totalwater potential, turgor potential, and stomatal resistance. A significant positive correlation existed between turgor potential and total water potential while osmotic potential remained fairly constant. There appeared to be no rapid, diurnal osmotic adjustment to maintain constant turgor, although there may have been some slight, long-term osmotic adjustment over the 2-week experimental period. When turgor approached zero, a depression of osmotic potential due to water loss through transpiration maintained turgor above zero. Stomatal resistance remained low throughout the day, even though total water potential dropped below –16 bars and turgor potential was below 2 bars. Stomatal resistance was negatively correlated with irradiance level but not with turgor potential.

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Douglas S. Chapman and Robert M. Augé

Understanding physiological drought resistance mechanisms in ornamentals may help growers and landscapers minimize plant water stress after wholesale production. We characterized the drought resistance of four potted, native, ornamental perennials: purple coneflower [Echinacea purpurea (L.) Moench], orange coneflower [Rudbeckia fulgida var. Sullivantii (Beadle & Boynt.) Cronq.], beebalm (Monarda didyma L.), and swamp sunflower (Helianthus angustifolius L.). We measured a) stomatal conductance of leaves of drying plants, b) lethal water potential and relative water content, and c) leaf osmotic adjustment during the lethal drying period. Maintenance of stomatal opening as leaves dry, low lethal water status values, and ability to osmotically adjust indicate relative drought tolerance, with the reverse indicating drought avoidance. Echinacea purpurea had low leaf water potential (ψL) and relative water content (RWC) at stomatal closure and low lethal ψL and RWC, results indicating high dehydration tolerance, relative to the other three species. Rudbeckia fulgida var. Sullivantii had a similar low ψL at stomatal closure and low lethal ψL and displayed relatively large osmotic adjustment. Monarda didyma had the highest ψL and RWC at stomatal closure and an intermediate lethal ψL, yet displayed a relatively large osmotic adjustment. Helianthus angustifolius became desiccated more rapidly than the other species, despite having a high ψL at stomatal closure; it had a high lethal ψL and displayed very little osmotic adjustment, results indicating relatively low dehydration tolerance. Despite differences in stomatal sensitivity, dehydration tolerance, and osmotic adjustment, all four perennials fall predominantly in the drought-avoidance category, relative to the dehydration tolerance previously reported for a wide range of plant species.

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Zhou Li, Yan Peng, and Bingru Huang

effects of γ-aminobutyric acid (GABA) on osmotic adjustment (OA) ( A ) under heat stress and ( B ) under drought stress in creeping bentgrass under normal water condition, heat stress, and drought stress. Means of four independent samples are presented

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Xuan Liu and Catherine Grieve

family, Plumbaginaceae, includes more than 50 halophytic Limonium species, many of which are known to complete their life cycles under hypersaline conditions [i.e., 56 dS·m −1 ( Aronson, 1989 )]. Osmotic adjustment is achieved in the cytoplasm of these

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Robert M. Augé, Xiangrong Duan, Jennifer L. Croker, Craig D. Green, and Will T. Witte

We compared the potential for foliar dehydration tolerance and maximum capacity for osmotic adjustment in twelve temperate, deciduous tree species, under standardized soil and atmospheric conditions. Dehydration tolerance was operationally defined as lethal leaf water potential (Ψ): the Ψ of the last remaining leaves surviving a continuous, lethal soil drying episode. Nyssa sylvatica and Liriodendron tulipifera were most sensitive to dehydration, having lethal leaf Ψ of –2.04 and –2.38 MPa, respectively. Chionanthus virginiana, Quercus prinus, Acer saccharum, and Quercus acutissima withstood the most dehydration, with leaves not dying until leaf psi dropped to –5.63 MPa or below. Lethal leaf Ψ (in MPa) of other, intermediate species were: Quercus rubra (–3.34), Oxydendrum arboreum (–3.98), Halesia carolina (–4.11), Acer rubrum (–4.43), Quercus alba (–4.60), and Cornus florida (–4.88). Decreasing lethal leaf Ψ was significantly correlated with increasing capacity for osmotic adjustment. Chionanthus virginiana and Q. acutissima showed the most osmotic adjustment during the lethal soil drying episode, with osmotic potential at full turgor declining by 1.73 and 1.44 MPa, respectively. Other species having declines in osmotic potential at full turgor exceeding 0.50 MPa were Q. prinus (0.89), A. saccharum (0.71), Q. alba (0.68), H. carolina (0.67), Q. rubra (0.60), and C. florida (0.52). Lethal leaf Ψ was loosely correlated with lethal soil water contents and not correlated with lethal leaf relative water content.