Genotype, Temperature, and Fall-applied Ethephon Affect Plum Flower Bud Development and Ovule Longevity

Abstract

<jats:p>Flower bud growth and ovule longevity of plum <jats:italic>(Prunus domestics</jats:italic> L.) cultivars Italian and Brooks and the effects of fall-applied ethephon and of temperature were studied. Fresh and dry weights of terminal flower buds were measured at l-week intervals from 50 days to 1 day before bloom in 1988. Buds were also analyzed for N, P, K, Ca, and B. After bloom, ovule longevity was determined using a fluorescence method after staining with aniline blue. Ovule longevity was determined in 1990 using shoots excised at full bloom from untreated and ethephon-treated trees of both cultivars and held in growth chambers for 18 days at 5, 10, 15, or 20C. `Brooks' flower buds showed a higher accumulation of fresh and dry weight than `Italian', and ethephon reduced bud weights in both cultivars. Ethephon did not affect mineral content of flower buds of `Brooks', but `Italian' flower buds contained a higher concentration of Ca and a lower concentration of P when treated with ethephon. Boron content was higher in the ethephon-treated buds of `Italian' trees on some sampling dates. Ovule longevity was higher for `Brooks' than for `Italian' in both years. Ethephon treatment delayed ovule senescence in `Italian' flowers, but had little or no effect on `Brooks' flowers. Increasing temperatures induced faster ovule senescence in both cultivars. Chemical name used. 2-chloroethylphosphonic acid (ethephon).</jats:p>

Multiple Regression Models for the Analysis of Potential Cultivation Areas for Japanese Plums

“…High temperatures at bloom clearly reduced potential yield. This finding agrees with that of Moreno et al (1992), who found that increasing temperatures induced faster ovule senescence and consequently reduced fruit set. These two cultivars are considered to have a high chilling requirement because of their late bloom dates (Fig.…”

“…In those years when temperatures during bloom were lower and higher than a PC value of 0.4, yields were reduced, suggesting that it is an optimum temperature for fruit set. High temperatures reduce ovule longevity (Moreno et al, 1992) and low temperatures retard pollen tube growth (Williams, 1970); therefore, fruit set can be diminished by a failure in fertilization derived from inappropriate temperatures at bloom. This cultivar group had the lowest chilling requirement, 700 chill units (Richardson et al, 1974), which can be supported by the fact that these trees bloomed earlier than cultivars in the other groups ( Fig.…”

“…Plum yield instability has been reported. For example, 'Brooks' has a more consistent annual production than 'Italian' (Moreno et al, 1992). Yields varied significantly among years in a Japanese plum germplasm collection in Zacatecas without any apparent cause, such as frost damage, alternate bearing, or tree age (Rumayor-Rodríguez et al, 1991).…”

“…Temperatures during and after full bloom also may affect yield by reducing fruit set of deciduous fruit trees. The effects of temperatures on pollination (Williams, 1970), pollen tube growth (Keulemans, 1984), ovule longevity (Moreno et al, 1992), and stigma receptivity (Pimienta et al, 1983) have been reported.…”

Lack of Fruit Set Caused by Ovule Degeneration in Japanese Plum

“…When pollen arrives on the stigma, it induces ethylene production (Johnson and Polito, 2007), which has been reported to induce the arrest of ovule development (Zhang and O'Neill, 1993). Female sterility in Prunus can be also induced by the application of different external chemical treatments (Beppu et al, 2001;Herrero et al, 2000;Morenol et al, 1992;Stösser and Anvari, 1982). Regardless of the factor causing ovule degeneration, it seems that different genotypes have a different response, because in one of the orchards analyzed, other cultivars had normal fruit sets (data not shown).…”