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Kenneth R. Schroeder and Dennis P. Stimart

Evaluation of leaf stomatal numbers and postharvest water loss indicate these are important factors in Antirrhinum majus (snapdragon) cut flower postharvest longevity (PHL). Cut flowers with 9 days longer PHL had 53% fewer leaf stomata. Long PHL is associated with an early reduction in transpiration followed by low steady transpiration. Short-lived genotypes had a linear transpiration pattern over the period of PHL indicating poor stomatal control of water loss. Short-lived genotypes had 22% to 33% reductions in fourth quarter transpiration while long-lived genotypes had 2% to 8% reductions. In addition, short-lived genotypes had higher average fourth quarter cut flower weight losses compared to long-lived genotypes. Further investigation of stomatal numbers and functioning relative to PHL may provide breeders a rapid and nondestructive indirect selection method for PHL.

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William L. Bauerle* and Joe E. Toler

A multiplicative model of stomatal conductance was developed and tested in two functionally distinct ecotypes of Acer rubrum L. (red maple). The model overcomes the main limitation of the commonly used Ball-Berry model by accounting for stomatal behavior under soil drying conditions. It combined the Ball-Berry model with an integrated expression of abscisic acid-based control mechanisms (gfac). The factor gfac = exp(-β[ABA]L) incorporated the stomatal response to abscisic acid (ABA) concentration in the bulk leaf tissue [ABA]L into the Ball-Berry model by down-regulating the slope and coupled physiological changes at the leaf level with those of the root. The stomatal conductance (gs) down regulation is pertinent in situations where soil drying may modify the delivery of chemical signals to leaf stomates. Model testing results indicated that the multiplicative model was capable of predicting stomatal conductance under wide ranges of soil and atmospheric conditions in a woody perennial. Concordance correlation coefficients (rc) were high (between 0.59 and 0.94) for the tested ecotypes under three different environmental conditions (aerial, distal, and minimal stress). The study supported the use of the gfac factor as a gas exchange function that controlled water stress effects on gs and aided in the prediction of gs responses.

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

). These authors found that green kiwifruit ( A. deliciosa var. deliciosa ‘Hayward’) has a high transpiration rate with poor stomatal control. Green et al. (1989) reported that A. deliciosa transpires at night and this could account for up to 30% of

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Juan C Díaz, Kenneth Shackel, and Ellen Sutter

Apple plantlets were cultured in a MS medium with agar and transplanted to a soilless mix. Before transplanting, plantlets were acclimatized in a chamber where humidity was linearly decreased from 99% to 75% (21 C) over a period of four days. Gas exchange measurements were made at 95% RH (21 C) and at an irradiance of 350 μmol m-2 s-1. Leaf conductance (g1) was measured with a porometer and net photosynthesis (Pn) with an IRGA. At the end of the gas exchange measurements, shoot relative water content (RWC) was determined. The results showed that plant water status was an important factor for plant survival and growth after transplanting. Acclimatization before transplanting allowed the plant to maintain a higher RWC, probably because of a better stomatal control of transpiration. Such higher water status was associated with higher growth rates in acclimatized than in non-acclimatized plants. There was a positive correlation of RWC with both a and Pn. Transplanted plants had higher values of g1 and Pn compared to in vitro plantlets. Photosynthesis of in vitro plantlets was limited by both stomatal and nonstomatal factors.

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Andres A. Estrada-Luna, Fred T. Davies Jr., and Jonathan N. Egilla

Micropropagated chile ancho pepper (Capsicum annuum L. cv. San Luis) plants were transferred to ex vitro conditions to study plantlet performance and selected physiological changes that occur during acclimatization and post-acclimatization. The physiology of the plantlets was characterized by measuring leaf gas exchange and water status. Plant growth was determined by assessing plant height, leaf number, total leaf area, relative growth rate (RGR), and leaf, root, and stem dry mass. Measurements were taken at 0, 1, 2, 3, 6, 12, and 24 days after transplanting. After initial transplanting ex vitro to liner pots with soilless media, plantlet wilting was observed that correlated with reduced leaf relative water content (RWC). Water stress was partially alleviated by a reduction in stomatal conductance (gs), confirming that the in vitro formed stomata were functional and able to regulate transpiration (E) to minimize desiccation losses. Because of this stomatal control, plantlets had minimal transplant shock, recovered, and survived. Prior to transplanting, micropropagated plantlets showed heterotrophic/mixotrophic characteristics as indicated by low photosynthesis [(A) 4.74 μmol·m2·s-1]. During acclimatization, RWC, gs, E, and A were significantly lower 2 days after transplanting. However, within 6 days after transplanting, plantlets recovered and became autotrophic, attaining high A (16.3 μmol·m-2·s-1), gs, and E. The stabilization and improvement of plantlet water status and gas exchange during acclimatization and post-acclimatization closely correlated with dramatic increases in plantlet growth.

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Krista Shellie and D. Michael Glenn

distinguished by differences in hydraulic conductance ( Schultz, 2003 ) or by the degree to which Ψ L influences stomatal control at a given level of chemical signal ( Tardieu and Simonneau, 1998 ). The Ψ L of anisohydric plants is thought to be an artifact of

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Nauja Lisa Jensen, Christian R. Jensen, Fulai Liu, and Karen K. Petersen

.N. Jacobsen, S.E. Jensen, C.R. 2005a Stomatal control and water use efficiency of soybean ( Glycine max L. Merr.) during progressive soil drying Environ. Exp. Bot. 54 33 40 Liu, F. Jensen, C

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Anish Malladi and Jacqueline K. Burns

Stomatal control in tomato with ABA-deficient roots: Response of grafted plants to soil drying J. Expt. Bot. 53 1503 1514 Jackson, M.B. 2002 Long distance signaling from roots to shoots assesses: The flooding story J. Expt

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Nisa Leksungnoen, Paul G. Johnson, and Roger K. Kjelgren

before rewatering and timed by the depth (10 cm) in each depth over the total from all depths (100 cm). The same letters are not significantly different ( P < 0.05) in water use. Discussion Turfgrass has limited stomatal control over transpiration as a

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Michelle DaCosta and Bingru Huang

, suggesting that a low accumulation rate of ABA in leaves would be beneficial for the maintenance of photosynthesis during short-term drought. Cytokinins generally have antagonistic physiological effects with ABA, especially in stomatal control. Cytokinins