Foliar Application of Boron to Almond Trees Affects Pollen Quality
By A. Nyomora, P. Brown, K. Pinney, V. Polito. 2000
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The effect of boron (B) on in vivo and in vitro development of almond ( Prunus dulcis (Mill.) D.A. Webb (syn. P. amygdalus Batsch)) pollen and pollen tubes and the resultant effect on fruit set was studied in mature trees. The cultivars Mono (pistil donor) and Butte (pollinizer) in an orchard with low soil B in Fresno, California were sprayed with B at 0, 0.8, 1.7, or 2.5 kg·ha -1 during Fall 1993. Pollen viability as indicated by the fluorescein diacetate method (FDA) was >85% and was not affected by field-applied B, however, in vivo pollen germination and tube growth were enhanced by foliar-applied B. More effect of applied B on in vivo growth appeared as pollen tubes progressed toward the ovary. For in vitro germination, foliar-applied B reduced bursting of tubes, and addition of B to the culture media significantly increased pollen germination and pollen tube growth. Most commercial almond (Prunus dulcis (syn. P. amygdalus)) cultivars are self-unfruitful (Griggs 1953) and therefore need to be interplanted with cross-compatible, pollinizer cultivars to produce an appreciable crop (Hill et al., 1985). Important factors that a grower must consider when selecting cultivar and pollinizer combinations include bloom overlap and the capacity to produce pollen in sufficient quantity and quality. While genetic factors determine the ultimate potential of the pollinizer (Hill et al., 1985), environmental variables, including mineral nutrition of the plant, can influence the quantity and quality of the pollen produced and its subsequent performance. In some Prunus sp., including almond, the presence of pollen tubes in the transmitting tissue activates the final phases of ovule and megagametophyte development that lead to ovule receptivity (Herrero and Arbeloa, 1989; Pimienta and Polito, 1983). In almond, pollen tubes arrive at the obturator and there is a temporary cessation of their growth at this point. While pollen tube growth is arrested at the obturator, megagametophyte devel- opment is completed. Pollen tube growth resumes after megaga- metophyte differentiation is complete (Pimienta and Polito, 1983). Williams (1965) introduced the term effective pollination period (EPP) to describe the window of time during which pollination may result in fertilization. EPP incorporates stigma receptivity, ovule longevity and the time needed for pollen tubes to reach the ovule, i.e., the rate of pollen tube growth. Research leading to yield models by Brain and Landsberg (1981) in apple (Malus sylvestris (L.) Mill. var domestica (Borkh.) Mansf.), and DeGrandi-Hoffman (1989) in almond shows that fruit set is determined by the number of flowers per tree and EPP. In these models, the time taken by pollen tubes to reach the ovule is a primary attribute used to calculate predicted yields. In view of these relationships, optimal orchard management practices in a species such as almond, where maximum fruit set is desired, should aim at extending EPP to maximize fertilization success.
Subfields: Molecular Biology, Plant Science
View Paper: https://www.semanticscholar.org/paper/a93a96e8b962af4ef0263b2db0113071ae11e6c0
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Citations in the corpus
- Uptake of Hydrophilic Solutes Through Plant Leaves: Current State of Knowledge and Perspectives of Foliar Fertilization (2009, background): “, 2008), and effect on yield and quality parameters (Brown et al., 1996; Nyomora et al., 2000; Pestana et al., 2001; Wojcik and Szwonek, 2002; AlcarazLópez et al., 2004; Dong et al., 2005; Lester et al., 2006; Singh et al., 2007; Amiri et al., 2008).”