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J.M. Quintana, H.C. Harrison, J.P. Palta, J. Nienhuis, K. Kmiecik, and E. Miglioranza

Stomatal density of pods and leaves were determined for six commercial snap bean cultivars (Phaseolus vulgaris L. `Evergreen', `Hystyle', Labrador', `Tenderlake', `Top Crop', and `Venture') grown at three planting dates, in an attempt to find morphological traits that could be related to cultivar differences in pod Ca concentration. Snap beans were planted three times at ≈1-week intervals beginning 15 June 1995, and harvested 59 to 62 days after planting. Stomatal counts were performed using a microscope linked to a video camera, and Ca concentration determinations were made using atomic absorption spectrophotometry. Calcium concentration and stomatal density of leaf tissue was higher than that of pods. Cultivar differences for pod Ca concentration (P = 0.001) and stomatal density (P = 0.001) were observed although cultivars with higher pod stomatal density did not necessarily result in higher pod Ca concentration. Calcium concentration and stomatal density for leaves did not differ among cultivars. Stomatal density and Ca concentration of pods were positively correlated (R 2 = 0.37), while pod maturity was negatively associated to both pod Ca concentration (R 2 = 0.93), and pod stomatal density (R 2 = 0.99). The effect of planting dates was absent in pod Ca concentration and significant in pod stomatal density.

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William J. Martin and Dennis P. Stimart

Stomatal density during plant development and inheritance of the trait were investigated with the goal of utilizing stomatal density as a correlated trait to cutflower postharvest longevity in Antirrhinum majus L. Inbred P1 (stomatal index = 0.2) was hybridized to inbred P2 (stomatal index = 0.3) to produce F1 (P1 × P2), which was backcrossed to each parent producing BCP1 (F1 × P1) and BCP2 (F1 × P2). P1, P2, F1, BCP1, and BCP2 were used to examine changes in stomatal density with plant development and early generation inheritance. An F2 (F1 self-pollinated), and F3, F4, and F5 families, derived by self-pollination and single seed descent, were used to obtain information on advanced generation inheritance. Stomatal density was stable over time and with development of leaves at individual nodes after seedlings reached two weeks of age. Therefore, stomatal density can be evaluated after two weeks of plant development from a leaf at any node. Stomatal density is quantitatively inherited with narrow sense heritabilities of h2 F2:F3 = 0.47 to 0.49, h2 F3:F4 = 0.37 ± 0.06 to 0.60 ± 0.07, and h2 F4:F5 = 0.47 ± 0.07 to 0.50 ± 0.07.

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Michael A. Grusak and Kirk W. Pomper

Understanding the mechanisms that regulate xylem transport of calcium (Ca) to snap bean (Phaseolus vulgaris L.) pods could allow approaches to enhance pod Ca levels, and thereby improve the value of this food source for humans. Pods of greenhouse-grown plants of `Hystyle', `Labrador', `Tendergreen', `Green Crop', `BBL94', and `Gold Crop' were examined for stomatal density and rates of pod transpiration throughout pod development. Among pods ranging from 6 to 14 mm in diameter, Ca concentration and pod stomatal density varied inversely with increasing diameter in all cultivars; Ca concentration for pods of a given diameter also varied among cultivars. To assess the influence of pod stomatal density on pod transpiration, water loss was measured from detached pods of `Hystyle' and `Labrador', which have high and low pod stomatal densities, respectively. Pod transpiration rates were similar for the two cultivars, being ≈15% the rate measured in leaves under equivalent conditions, and comparable to rates of cuticular transpiration measured in leaves with closed stomates. These results suggest that pod stomates have no role, or have only a limited role, in pod transpiration. Pods of `Hystyle' and `Labrador' were placed in enclosures that maintained constant high- or low-humidity environments throughout pod development. For each cultivar, the high-humidity environment led to lower pod Ca concentrations, demonstrating that pod transpiration does have a significant impact on pod Ca accretion. However, `Hystyle' consistently exhibited higher pod Ca concentrations, relative to `Labrador', suggesting that differences in xylem sap Ca concentration may have been responsible for cultivar differences in pod Ca concentration.

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William J. Martin and Dennis P. Stimart

Stomatal density is being investigated as a highly correlated trait to postharvest longevity (PHL) and subsequently may be used for selection in early generations of breeding germplasm. To this end, leaf imprints were created from Antirrhinum majus L. (snapdragon) P1, P2, F1, BC1 (F1×P1), BC2 (F1×P2), F2, and F3 plants and evaluated for stomatal densities. Cut flowers of P1, P2, F1, BC1 (F1×P1), BC2 (F1×P2), and F3 were harvested after the first five flowers opened and evaluated for PHL. Additionally, cut flowers from these lines were evaluated for leaf surface area. Populations for evaluation were grown in the greenhouse in winter and spring 1999-2000 in a randomized complete-block design according to standard forcing procedures. Twenty-five cut flowering stems of each genotype were held in the laboratory in deionized water under continuous fluorescent lighting at 22 °C for PHL assessment. The end of PHL was defined as 50% of the flowers drying, browning, or wilting. Data will be presented on the correlation between stomatal density and PHL.

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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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N.C. Yorio, C.L. Mackowiak, R.M. Wheeler, and G.W. Stutte

The effects of elevated CO2 on stomatal density and index were investigated for five crop species currently being studied for NASA's Advanced Life Support program. Lettuce (cv. Waldmann's Green) and radish (cv. Giant White Globe) were grown at 400, 1000, 5000, or 10,000 μmol·mol–1 CO2, tomato (cvs. Red Robin and Reimann Philip 75/59) were grown at 400, 1200, 5000, or 10,000 μmol·mol–1 CO2, and wheat (cv. Yecora Rojo) and potato (cv. Denali) were grown at 400, 1000, or 10,000 μmol·mol–1 CO2 within controlled-environment growth chambers using nutrient film technique hydroponics. Leaf impressions were made by applying clear silicone-based RTV coating to the adaxial and abaxial leaf surfaces of three canopy leaves of each crop at each CO2 treatment. Impressions were examined using a light microscope, whereby the number of stomatal complexes and epidermal cells were counted to calculate stomatal density and stomatal index. Results indicate that stomatal density increased for lettuce and radish at 10,000 μmol·mol–1 CO2, whereas tomato density was highest at 1200 μmol·mol–1 CO2. Potato had the lowest density at 1000 μmol·mol–1 CO2, and there was no effect of CO2 on density for wheat. Stomatal index correlated with density for lettuce and tomato; however, stomatal index for radish, potato, and wheat was not influenced by CO2. This suggests that there may be a species-specific CO2 response to epidermal cell size that influences stomatal density and stomatal index.

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Maurus V. Brown, James N. Moore, and Patrick Fenn

Plasmopara viticola infects and sporulates through stomata of susceptible grape leaves. Sporulation, chlorosis, and necrosis ratings were made in 1994 and 1995 on grape selections and cultivars and Vitis species grown in a fungicide-free vineyard. Cellulose-acetate impressions were made of the abaxial leaf surfaces and stomata were carefully counted within a circle 100 μm in diameter under a light microscope. Leaves were rated as either pubescent or glabrous. There were significant differences among genotypes for sporulation, chlorosis, and necrosis for 1994 and 1995, with highly significant correlations over both years. Stomatal densities were significantly different, but there were no correlations among levels of downy mildew and stomata! densities. Pubescent leaves had significantly higher sporulation, chlorosis, and necrosis ratings for downy mildew than glabrous leaves over both years.

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Madhulika Sagaram, Leonardo Lombardini, and L.J. Grauke

differences in the lengths of growing season at their origins ( Wood et al., 1998 ). Studies conducted on ponderosa pine ( Pinus ponderosa Dougl. ex Laws) reported intraspecific variation for anatomical and physiological traits such as stomatal density [SD

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Juan M. Quintana, Helen C. Harrison, James Nienhuis, and Jiwan Palta

Pod stomatal density and Ca concentration levels were analyzed for six commercial snap bean cultivars harvested at four planting dates in an attempt to find morphological traits that are related to cultivar differences in pod Ca concentration. The experimental layout was a randomized complete-block design with two replications per planting date, all grown in one location. Snap beans were planted at 1 week intervals beginning 9 June 9 1995 and were harvested in August. Sampling consisted of five pod sizes (1, 2, 3, 4, and 5 according to commercial standards) from each genotype. Stomatal countings were performed using a microscope linked to a television camera. Determinations for pod Ca concentration were made using an atomic absorption spectrophotometer. No differences were detected for pod Ca concentration among planting dates, although there were differences for pod Ca concentration and stomata density among cultivars. Pod stomatal density was positively correlated to pod Ca concentration (R 2 = 0.60), while pod maturity appeared to be negatively correlated to pod Ca concentration (R 2 = 0.37) and pod stomatal density (R 2 = 0.49).

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Madhulika Sagaram, Leonardo Lombardini, and L.J. Grauke

. This study was undertaken to characterize the leaf anatomic features of three pecan cultivars at various geographical locations and to investigate the influence of cultivar and environment on stomatal density and epidermal cell density. Materials