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Khalil R. Jahed and Peter M. Hirst

seed set), and the other fuses with the two polar nuclei to produce the endosperm. Pollen source and temperature have a tremendous influence on the rate of pollen tube growth. Jackson (2003) and Petropoulou and Alston (1998) proposed that the

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Chao Gao, Deyi Yuan, Ya Yang, Bifang Wang, Dongming Liu, and Feng Zou

= 400 μm. CC = canal cell; Co = cortex; En = endodermis; Ep = epidermis; Ov = ovule; Pa = papilla; PT = pollen tube; TT = transmitting tissue; VB = vascular bundle. Therefore, in this study, we explored the processes of pollen tube growth and

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Candace N. DeLong, Keith S. Yoder, Leon Combs, Richard E. Veilleux, and Gregory M. Peck

Apple pollination occurs when pollen is transferred, often by an insect vector, from the anthers of one blossom to the stigma of another. After pollen grains are deposited, they are rehydrated by stigmatic secretions, and pollen tube growth begins

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Thomas M. Kon, James R. Schupp, Keith S. Yoder, Leon D. Combs, and Melanie A. Schupp

( Byers, 2003 ). An inherent challenge with blossom thinning is the short period of time that growers have to apply treatments over large acreage ( Moran and Southwick, 2000 ). Models have been developed to estimate the rate of pollen tube growth in apple

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Keith Yoder, Rongcai Yuan, Leon Combs, Ross Byers, Jim McFerson, and Tory Schmidt

and fertilization through damaging the anthers, stigma, and style of flowers or inhibiting pollen tube growth in the style of flowers and are applied when some, but not all, flowers are fertilized ( Fallahi and Willemsen, 2002 ; Greene, 2002

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Nachida Ben-Njima

Group-author : R. Socias i Company

Pollen tube growth was studied in 10 almond [Prunus amygdalus Batsch, syn. P. dulcis (Mill.) D.A. Webb] selections of the Zaragoza breeding program, whose main objective is the development of self-compatible cultivars. Self-compatibility was evident in eight of the selections, as indicated by the fact that pollen tube growth was similar following self- and cross-pollination. In the other two selections, pollen tube growth differed following self- and cross-pollination, one showing self-incompatibility and the other an irregular progression of crossed pollen tubes. The importance of the style in sustaining pollen tube growth was evident, and pollen tube growth was influenced by style type.

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Thomas M. Kon, Melanie A. Schupp, Hans E. Winzeler, and James R. Schupp

interaction of the intensity, duration, and rate of temperature change ( Wahid et al., 2007 ). As demonstrated with an ornamental lily, pollen tube growth in vivo was temporarily arrested with 10-s exposure to 45 °C ( Pierson et al., 1993 ). Unlike leaves and

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Levava Roiz, Uzi Ozeri, Raphael Goren, and Oded Shoseyov

Aspergillus niger B-1 (CMI CC 324626) extracellular RNase (RNase B1) was purified to homogeneity. It was found to contain two isoforms of 32- and 40-kDa glycoproteins, sharing a 29-kDa protein moiety. Optimal RNase activity was observed at 60 °C and pH 3.5. In `Almog' peach [Prunus persica (L.) Batsch (Peach Group) `Almog'] and `Murcott' tangerine (Citrus reticulata Blanco `Murcott') the enzyme inhibited pollen germination and pollen tube growth in vitro as well as in vivo. In field experiments, spray application of the RNase caused a reduction in `Fantasia' nectarine [Prunus persica (L.) Batsch (Nectarine Group) `Fantasia'] fruit set and interfered with embryo development. The biological effect of the RNase may be of horticultural value, due to its potential to control fertilization.

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Thomas M. Kon, Melanie A. Schupp, Hans E. Winzeler, and James R. Schupp

strategy, the effects of TS temperature and treatment duration on pollen tube growth in vivo and visible spur leaf injury were evaluated. Materials and Methods Trials were conducted in 2014 and 2015 at the Pennsylvania State University’s Fruit Research and

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Anson E. Thompson, David A. Dierig, and Jon P. Rebman

Vernonia galamensis (Cass.) Less. (Asteraceae) constitutes a species complex of six subspecies, one of which contains four varieties. Crossing barriers between the subspecies and varieties are being examined. In the analysis of microspore mother cells, no differences in chromosome number (n=9) were found, and meiosis appeared to be normal within and between subspecies. However, an extended delay in time was observed in all subspecies in which chromosomes remained condensed during the post-meiotic tetrad stage. No apparent effect on pollen formation or pollen tube growth was observed from this unusual phenomenon. Self and reciprocal intraspecific crosses are being made, and pollen tube growth into the ovules assessed by fluorescent microscopy. These techniques are being used to characterize self-incompatibility within subspecies and varieties, and to determine the possible barriers to pollen tube growth and autofertility.