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  • Author or Editor: Ben T. Iwakiri x
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Abstract

A 4-year study of the bloom periods of pear trees with different types of rootstocks indicates that, under the range of chilling conditions characteristic of California’s major pear districts, rootstock has little or no influence on scion chilling requirements.

Open Access

Abstract

Pollen from 5 different sources did not alter fruit size or time of maturity of ‘Kerman’ pistachio (Pistacia vera L.). Degree of shell (endocarp) dehiscence was modified with some pollen sources but was found to be related directly to kernel development rather than to type of pollen. Thus, there were no manifestations of metaxenia. Xenia, as exhibited by reduced kernel length and dry weight, did occur, however, following the use of P. atlantica and hybrid pollen.

Open Access

Abstract

Shell dehiscence in pistachio (Pistacia vera L.) is dependent upon seed growth and development, as blank nuts fail to dehisce. Evidence is presented indicating that dehiscence is not the result of the seed exerting physical force on the surrounding shell, as has been suggested, but is a manifestation of abscission that is triggered by a substance(s) emanating from the seed.

Open Access

Abstract

Pronounced vegetative apical dominance in pistachio was exhibited by sparse lateral branching and by response to conventional pruning. This dominance necessitates a pruning procedure different from other deciduous fruit and nut species. Marked apical dominance also occurred both in the patterns of fruit set in the inflorescence as a whole and in the individual branches composing it. The percentage of fruit set was highest in the apical portion of the inflorescence and generally decreased to the proximal portion. Similarly, although only 8% of the flowers on the branches of the inflorescence occupied a terminal position, 60% of the total fruit produced were terminal.

Open Access

Abstract

Trunk cross-sectional area of ‘Kerman’ pistachio trees on Pistacia atlantica Desf. seedling rootstocks varied widely after 24 years. Average annual nut yield was positively related to trunk cross-sectional area. Degree of shell splitting and blank nut production also were influenced by rootstock. Two trees were identified that were the most vigorous, had the greatest yields, and produced excellent crops annually in contrast to the others that exhibited severe biennial bearing.

Open Access

Abstract

Data collected 2 consecutive years revealed that 30% to 38% of the inflorescence buds of ‘Kerman’ pistachio (Pistacia vera L.) abscised mainly during an initial 5- to 6-week period from trees devoid of fruit. Bearing trees, by contrast, progressively dropped 99% of their buds during a 10- to 12-week period. Abscission during the initial 5- to 6-week period in bearing and nonbearing trees is apparently the result of a stimulus originating in the roots. Continued abscission during the subsequent 5- to 6- week period coincided with the initiation and growth and development of the kernel. It appears, therefore, that a stimulus originating in the fruit (kernel) is responsible for the second phase of a two-phased abscission process.

Open Access

Abstract

‘Bartlett’ spurs carrying seedless or seeded fruits produced relatively high percentages of flower buds. Spurs carrying seedless pears for 31 days after bloom produced more flower buds than did spurs carrying seeded pears. Also, the exudate from seedless pears had more growth-promoting activity. Beyond 31 days there were no consistent differences in flower bud formation in spurs carrying seedless vs. seeded pears. Carrying seeded pears 31 days largely inhibited flower bud initiation in ‘Winter Nelis’. There was an inverse relationship between flower buds and seeds in fruits on spurs of both varieties defruited 61 days after bloom. The relationship was not distinct for spurs carrying fruits longer. Fluctuations in the growth-promoting activity of the fruit exudate indicate that the hormonal status, at the time the spur was defruited, influenced flower bud formation more than did number of fruits, seeds, or length of fruit-carrying period.

Open Access

Abstract

Ethephon did not increase shell dehiscence in pistachio, Pistacia vera L., and caused excessive gum exudation from the trunk and framework branches and severe flower bud abscission.

Open Access

Abstract

Viability of walnut, Juglans regia L., pollen was not diminished by storage at subfreezing temperature, as previously indicated. Pollen stored 20 days at −19°C effected high percentages of fruit set in the orchard in 1969. Fruit set of the bagged flowers was relatively low in 1970, but the set effected by pollen stored a year at −19°C was not significantly different from that effected by fresh pollen. Laboratory tests indicated less than 1% germination for both freshly dehisced and stored pollen, and were unreliable for indicating the ability of walnut pollen to effect fertilization.

Open Access

Abstract

Branch units of 20 ‘Bartlett’ pear trees were sprayed with 2-chloroethylphosphonic acid (Ethrel) at 250, 500, or 1000 ppm or with cycloheximide (beta-[2-(3,5-dimethyl-2-oxocyclohexyl)-2-hydroxyethyl] glutarimide) at 3, 5, or 20 ppm a wk before the beginning of normal harvest to weaken the abscission layer to facilitate mechanical harvest. Half the trees had been sprayed with naphthaleneacetic acid (NAA) to prevent preharvest drop. Nine days after application, Ethrel at 1000 ppm had significantly reduced the fruit removal force (FRF) on trees that had received no NAA. In contrast, the presence of NAA evidently nullified the abscission-promoting effect of Ethrel. All other treatments failed to reduce FRF significantly. None of the sprays caused discernible phytotoxic effects or hastened fruit maturity. However, after storage for 50 days at 0°C, 17% to 50% of the fruits that received Ethrel at 500 or 1000 ppm, broke down during ripening. Cycloheximide caused no breakdown, but 20% to 80% of the fruits aprayed with 5 or 20 ppm had necrotic spots at the calyx end.

Open Access