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Susan L. Steinberg, Jayne M. Zajicek, and Marshall J. McFarland

Growth of potted Ligustrum was controlled by uniconazole at 3.0 mg a.i./pot. Uniconazole inhibited growth by inducing shorter internodes with smaller diameter and by reducing secondary branching and new leaf production. As a result, the total leaf area of the treated plants was 6396 less than the control plants. The chlorophyll content of recently expanded leaves was 27% lower in treated than in control plants, even though there were no visual differences in leaf color. Leaves of treated plants also had a 28% higher stomatal density than the control. The liquid flow conductance of Ligustrum was 3.7 × 10-14 m·s-1·Pa-1 and was similar for plants in both treatments. Differences in daily water, use between the two treatments began to appear at the same time as differences in growth. Total water use of treated plants was 13% less than that of the control. When daily water use was normalized on a-leaf-area basis, water use between treatments was similar, suggesting that differences in total water use were primarily due to differences in leaf area. For plants in both treatments, peak sap flow rates in the main trunk ranged between 60 and 100 g·h-1·m-2. Leaf conductance, transpiration rates, and water potential were also similar for treated and control plants. Chemical name used: (E)-1-(4-chlorophenyll) -4,4, -dimethyl-2-(l,2,4-triazo1-l-y1)-l-penten-3-ol (uniconazole).

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Renate Karle, Constance A. Parks, Maureen C. O'Leary, and Thomas H. Boyle

Spontaneous chromosome doubling occurred in shoot apices of two diploid (2n = 22) Hatiora ×graeseri Barthlott ex D. Hunt (Easter cactus) clones and yielded stable periclinal cytochimeras with a diploid epidermis and tetraploid subepidermis. The cytochimeras produced disomic gametes (n = 22) and displayed tetrasomic inheritance at polymorphic isozyme loci. Diploid clones were highly self-incompatible (SI) but both cytochimeras were self-compatible (SC). Analysis of pollen tube growth in selfed or outcrossed styles revealed that polyploidy altered the incompatibility phenotype of pollen without affecting the incompatibility phenotype of the pistil. Morphological data (guard cell length, stomatal density, and pollen diameter), segregation ratios at isozyme loci, and fruit/seed yields indicate that S1 progeny are SC, nonchimeral, and tetraploid. Breakdown of the SI system in the cytochimeras was attributed to formation of compatible heteroallelic pollen. These results provide a rational explanation for the correlation between ploidy level and breeding behavior in cacti. Production of SC autotetraploid clones from SI diploids by chromosome doubling may be useful in development of cacti as fruit crops.

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Susan M. Stieve and Dennis P. Stimart

Eighteen commercially used white Antirrhinum majus (snapdragon) inbreds, a hybrid of Inbred 1 × Inbred 18 (Hybrid 1) and an F2 population (F2) of Hybrid 1 were evaluated for stomatal size and density and transpiration rate to determine their affect on postharvest longevity. Stems of each genotype were cut to 40 cm, placed in distilled water and discarded when 50% of florets wilted or browned. Postharvest longevity of inbreds ranged from 3.7 to 12.9 days; Hybrid 1 and the F2 averaged 3.0 and 9.1 days postharvest, respectively. Leaf impressions showed less than 3% of stomata were found on the adaxial leaf surface. Inbred abaxial stomatal densities ranged from 128.2 to 300.7 stomata mm-2; Hybrid 1 and the F2 averaged 155 and 197 stomata mm-2, respectively. Transpiration measurments on leaves of stems 24 hr after cutting were made with a LI-COR 1600 Steady State Porometer. Statistical analysis showed inbreds were significantly different based on postharvest longevity, stomatal size and density and transpiration of cut stems.

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Nihal C. Rajapakse and John W. Kelly

Transpiration rates of chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] plants grown under spectral filters were evaluated as part of an investigation on using light quality to regulate plant growth. The 6% CuSO4·5H2O spectral filter reduced photosynthetic photon flux density in red (R) and far red (FR) wavelengths and increased the R: FR and blue (B): R ratios (B = 400 to 500 nm; R = 600 to 700 nm; FR = 700 to 800 nm) of transmitted light relative to the water (control) filter. After 28 days, cumulative water use of plants grown under CuSO4 filters was ≈37% less than that of control plants. Transpiration rates were similar among plants grown under CuSO4 and control filters when expressed as leaf area, a result suggesting that the reduced cumulative water loss was a result of smaller plant size. Plants grown under CuSO4 filters had slightly lower (10%) stomatal density than control plants. Light transmitted through CuSO4 filters did not alter the size of individual stomata; however, total number of stomata and total stomatal pore area per plant was ≈50% less in plants grown under CuSO4 filters than in those grown under control filters due to less leaf area. The results suggest that altering light quality may help reduce water use and fertilizer demands while controlling growth during greenhouse production.

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Cheryl R. Hampson, Anita N. Azarenko, and John R. Potter

In hazelnut (Corylus avellana L.), vigorous vegetative growth and traditional orchard practices that include little or no pruning combine to produce a dense, shady canopy. A study designed to quantify the effect of shade on reproduction and photosynthetic rate in this shade-tolerant species was undertaken to assess whether some degree of pruning might improve productivity. Shade cloth was used to exclude 30%, 47%, 63%, 73%, or 92% of ambient sunlight from whole `Ennis' and `Barcelona' trees from mid-May until harvest. Photosynthetic light response curves were obtained for leaves that had developed in full sunlight, deep inside the canopy of unshaded trees, or in 92% shade. Light-saturated net photosynthetic rates were 12.0, 6.1, and 9.3 μmol·m-2·s-1 of CO2 and dark respiration rates were 2.0, 1.1, and 0.7 μmol·m-2·s-1 of CO2, respectively, for the three light regimes. Light-saturated photosynthetic rates of leaves from 30% or 63% shade differed little from the control (0% shade). Area per leaf increased by 49% and chlorophyll concentration (dry weight basis) by 157% as shading increased from 0% to 92%. Shading to 92% reduced specific leaf weight (68%), stomatal density (30%), light compensation point (69%), and dark respiration rate (63%) compared to controls. Female inflorescence density declined by about one-third and male inflorescence density by 64% to 74% in the most heavily shaded trees of both cultivars compared to controls. Shade was more detrimental to yield than flowering: yield per tree dropped by >80%, from 2.9 to 3.4 kg in full sun to 0.6 to 0.9 kg in 92% shade. Shade reduced yield primarily by decreasing nut number and secondarily by decreasing nut size. The incidence of several kernel defects increased as shade increased. Therefore, hazelnut leaves showed considerable capacity to adapt structurally and functionally to shade, but improving light penetration into the canopy would probably increase orchard productivity.

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Marco Beyer and Moritz Knoche

Rain-induced cracking of sweet cherry (Prunus avium L.) fruit is thought to be related to water absorption through the fruit surface. Conductance for water uptake (gtot. uptake) through the fruit surface of `Sam' sweet cherry was studied gravimetrically by monitoring water penetration from a donor solution of deionized water through segments of the outer pericarp into a polyethyleneglycol (PEG) containing receiver solution. Segments consisting of cuticle plus five to eight cell layers of epidermal and hypodermal tissue were mounted in stainless steel diffusion cells. Conductance was calculated from flow rates of water across the segment and the difference in osmotic potential between donor and receiver solution. Flow rates were constant up to 12 hours and decreased thereafter. A log normal distribution of gtot. uptake was observed with a median of 0.97 × 10-7 m·s-1. Further, gtot. uptake was not affected by storage duration (up to 71 days) of fruit used as a source of segments, thickness of segments (range 0.1 to 4.8 mm), or segment area exposed in the diffusion cell. Osmolality of the receiver solution in the range from 1140 to 3400 mmol·kg-1 had no effect on gtot. uptake (1.45 ± 0.42 × 10-7 m·s-1), but gtot. uptake increased by 301% (4.37 ± 0.46 × 10-7 m·s-1) at 300 mmol·kg-1. gtot. uptake was highest in the stylar scar region of the fruit (1.44 ± 0.16 × 10-7 m·s-1) followed by cheek (1.02 ±0.21 × 10-7 m·s-1), suture (0.57 ±0.17 × 10-7 m·s-1) and pedicel cavity regions (0.22 ±0.09 × 10-7 m·s-1). Across regions, gtot. uptake was related positively to stomatal density. Extracting total cuticular wax by dipping fruit in chloroform/methanol increased gtot. uptake from 1.18 ± 0.23 × 10-7 m·s-1 to 2.58 ± 0.41 × 10-7 m·s-1, but removing epicuticular wax by cellulose acetate stripping had no effect (1.59 ± 0.28 × 10-7 m·s-1). Water flux increased with increasing temperature (range 20 to 45 °C). Conductance differed between cultivars with `Hedelfinger' sweet cherry having the highest gtot. uptake (2.81 ± 0.26 × 10-7 m·s-1), followed by `Namare' (2.68 ± 0.26 × 10-7 m·s-1), `Kordia' (0.96 ± 0.14 × 10-7 m·s-1), `Sam' (0.87 ± 0.15 × 10-7 m·s-1), and `Adriana' (0.33 ± 0.02 × 10-7 m·s-1). The diffusion cell system described herein may be useful in analyzing conductance in water uptake through the fruit surface of sweet cherry and its potential relevance for fruit cracking.

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Yayan Feng, Leifeng Xu, Panpan Yang, Hua Xu, Yuwei Cao, Yuchao Tang, Suxia Yuan, and Jun Ming

genetic differences from their diploid counterparts ( Lokker et al., 2004 ), including morphological and cytological changes, reflected in parameters such as the leaf shape index, stomatal density, and guard cell size, which can directly affect metabolism

Open access

Fan-Hsuan Yang, Lisa W. DeVetter, Bernadine C. Strik, and David R. Bryla

. Each measurement required 5 to 10 min to obtain a stable reading. Stomatal density and distribution. The number of stomata on the berries was counted using a light microscope (model DM 2500; Leica, Wetzlar, Germany). To prepare the samples, six berries

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Yong Ha Rhie, Seonghwan Kang, and Jongyun Kim

= 4). Stomatal density responds to environmental factors, such as drought and elevated CO 2 concentration ( Xu and Zhou, 2008 ). In general, plants subjected to severe drought stress have low stomatal density as compared with plants grown in well

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Guilherme Locatelli, Rafael Pio, Rayane Barcelos Bisi, Filipe Bittencourt Machado de Souza, Mariana Thereza Rodrigues Viana, Daniela da Hora Farias, Evaristo Mauro de Castro, and Carolina Ruiz Zambon

cultivars exhibited similar equatorial diameters in the stomata. Table 3. Polar diameter of the stomata (POD), equatorial diameter of the stomata (EQD), stomatal functionality (FUN) (POD/EQD ratio), and stomatal density (DEN) of apple cultivars as estimated