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Huan-Keng Lin, Tzu-Yao Wei, Chin-Mu Chen and Der-Ming Yeh

. and Clematis maritima L., primary phloem fiber and collenchyma are displaced outward by plant development, which led to disrupting the mechanical integrity, but not in semiself-supporting Clematis recta L. ( Rowe et al., 2004 ). Modulus of

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Michele R. Warmund, Billy G. Cumbie and Mark V. Coggeshall

seedlings ranged from 6% to 93%. For intraspecific grafts of Chinese chestnut, few unions were formed and 6% to 10% of the trees survived after 6 months when side veneer graft cuts were made through phloem fibers in rootstock stems. Because grafting success

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Gary L. McDaniel, Effin T. Graham and Kathleen R. Maleug

The effects of growth-retarding chemicals on stem anatomy were compared on poinsettia (Euphorbia pulcherrima Wind. `Annette Hegg Dark Red'). Micrographic examinations revealed that secondary walls of nonsclerotic phloem fiber cells were either completely or greatly reduced by retardant treatment. Wall thickening of phloem fiber cells was eliminated by paclobutrazol foliar sprays at 25 mg·liter-1. Fiber cell development was reduced, but not eliminated, by sprays of chlormequat and ancymidol at standard rates, while the triazole uniconazole at 10 mg·liter-1 permitted only limited fiber wall thickening. Chemical names used: (2-chloroethyl)-trimethyl ammonium chloride (chlormequat); α -cyclopropylα- (4-methoxyphenyl) -5-pyrimidine methanol (ancymidol); (E)-(p -chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl-1-penten-3-ol (uniconazole): and (R*,R*)- β -[(4-chlorophenyl)methyl]- α -(1,1-dimethylethyl)- 1 H-1,2,4,triazole-1-ethanol (paclobutrazol).

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Mack Thetford, Stuart L. Warren', Frank A. Blazich and Judith F. Thomas

Uniconazole was applied as a foliar spray at 0, 90, 130, 170, or 210 ppm to rooted stem cuttings of `Spectabilis' forsythia (Forsythia xintermedia Zab.) potted in calcined clay. Uniconazole resulted in higher total leaf chlorophyll (chlorophyll + chlorophyll,) concentration and a decreased ratio of chlorophyll a: b. Stomata1 density of the most recently matured leaves increased linearly with increasing uniconazole concentration 40, 60, and 100 days after treatment (DAT). The number of stomata per leaf (stomata1 index) increased linearly with increasing concentration of uniconazole throughout the initial 100 DAT. Uniconazole suppressed stomata1 length at all sampling dates and the level of suppression increased with increasing concentration of uniconazole from 20 to 100 DAT. Stomata1 width was suppressed by uniconazole at 40 DAT. Leaves developed after uniconazole application had higher levels of net photosynthesis when measured 55, 77, and 365 DAT. Stomata1 conductance for uniconazole-treated plants was higher compared to nontreated control (0 mg·liter-1) plants when measured 49, 55, 77, and 365 DAT. Initiation of secondary xylem for stem tissues of uniconazole-treated plants was suppressed and expansion of xylem vessel length and width was less. Secondary phloem tissues of stems from uniconazole-treated plants contained larger numbers of phloem fibers having smaller cross sectional areas than phloem fibers of controls. Chemical name used: (E)-1-(p-Chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-01 (uniconazole).

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Hongwen Huang, J.D. Norton, G.E. Boyhan and B.R. Abrahams

Graft compatibility was investigated for 15 Chinese chestnut (Castanea mollissima Bl.) cultivars, nine American chestnut [C. dentata (Marsh.) Borkh.] selections, six Japanese chestnut (C. crenata Sieb.) cultivars, and two putative Japanese hybrids on two known rootstocks of Chinese chestnut. Intraspecific grafting of Chinese chestnut resulted in 80% success after two growing seasons. An unusual anatomical structure of the chestnut stem had a significant effect on graft success. The phloem fiber bundles related to graft failure are described in the study. Interspecific grafts of seven American and five Japanese chestnut selections resulted in ≥70% success. The putative Japanese hybrids had a significantly lower success rate (<50%) regardless of rootstocks. A marked graft incompatibility was found in one Japanese/Chinese and two American/Chinese combinations. Graft incompatibility related to morphological abnormalities at the graft union was also observed in interspecific grafts. Comparisons of cambial isoperoxidase isozymes between successful and unsuccessful grafts did not support the hypothesis that peroxidase isozymes are indicators of rootstock-scion compatibility. The results suggest that genetic incompatibility is not a major cause of graft failure in Chinese chestnut.

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Mary Jean Welser and Martin C. Goffinet

Grapevine yellows is a destructive, worldwide disease of grapevines that is caused by a phytoplasma, a bacterium-like organism that infects and disrupts the vascular system of shoots. The North American form of grapevine yellows (NAGY) has been observed in New York State since the mid-1970s and in Virginia since the mid-1990s. Symptoms duplicate those of vines suffering from an Australian disease complex known as Australian grapevine yellows (AGY). We sought to determine if infected `Chardonnay' vines have common anatomical characteristics across the three regions. At each geographic site in late summer, 2003–04, leaf and internode samples were taken from younger green regions of shoots and from mature basal regions in the fruiting zone. These were processed for histology. The anatomy of each organ type was compared between locations on the shoot, between geographic locations, and between affected and normal shoots. The phloem was the only tissue universally affected in vines with NAGY or AGY symptoms. In stem internodes, both primary phloem and secondary phloem showed many senescent cells, abnormally proliferated giant cells, and hyperplasia. In affected secondary phloem there was disruption of the radial files of cells that normally differentiate from the cambium into mature phloem cell types. Normal bands of secondary phloem fibers (“hard phloem”) in internodes were weak or absent in affected vines. Leaves also had disrupted phloem organization but near-normal xylem organization in vines with symptoms. Leaves of infected vines frequently showed a disruption of sugar transport out of the leaf blades, manifested by a heavy buildup of starch in chloroplasts of mesophyll cells and bundle-sheath cells.

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J. Naalamle Amissah, Dominick J. Paolillo Jr and Nina Bassuk

sclerenchyma sheath. For each age at time of cutting, a significantly lower percentage of parenchymatous gaps (thus, a greater proportion of phloem fibers) was found in the perivascular region of Q. macrocarpa compared with that of Q. bicolor ( Table 1

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Bhaskar Bondada

of the cluster framework, it mostly accumulated and distributed uniformly in the hypodermal cells; however, patchy intense clumps occurred in the cortical layers adjoining the epidermis and the primary phloem fiber cap, although with less intensity

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Fan Cao, Xinwang Wang, Zhuangzhuang Liu, Yongrong Li and Fangren Peng

discontinuity is absent. According to the primary phloem fiber cell group structure from pecan stem crosscuts of the anatomic structure, it is known that phloem fiber cells have little effect on the inhibition of pecan adventitious root primordia formation, and

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Shuguang Wang, Yongpeng Ma, Chengbin Wan, Chungyun Hse, Todd F. Shupe, Yujun Wang and Changming Wang

elongation. Moreover, IAA was also involved in secondary cell wall deposition in both parenchymal and fiber cells. Literature Cited Aloni, R. 1979 Role of auxin and gibberellin in differentiation of primary phloem fibers Plant Physiol. 63 609 614 Aloni, R