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  • Author or Editor: Julian C. Crane x
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Abstract

This subject has been reviewed periodically by Nitsch (60) in 1953, Luckwill (53) in 1959, Leopold (47) in 1962, and lastly by Crane (19) in 1964. It has been pointed out repeatedly that the seeds in fruits are rich sources particularly of auxins, but also of gibberellins and cytokinins as well. Various types of evidence would indicate that these hormones emanating from the seeds stimulate growth of the fruit tissues surrounding them and also control fruit abscission. For example, in many fruits marked correlations exist between seed number and ultimate fruit size and also between seed distribution and fruit shape. Fruits that absciss prematurely are usually multi-seeded ones with a lower seed content than normal, or are single or multi-seeded fruits in which the seeds abort.

Open Access
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Abstract

During a 4-year period, ‘Kerman’ pistachio trees (Pistacia vera) produced an average of 26% blank nuts. Production of blanks by individual trees remained relatively constant from year to year and was not associated with yield or position of the trees in relation to pollinators. Blank production was also found to be a characteristic of P. atlantica Desf. and P. chinensis Bunge. Results demonstrated that production of blanks, at least in ‘Kerman’, is partly the result of parthenocarpy.

Open Access
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Abstract

The phenomenon of abscission in plants is influenced by several environmental factors (1). Leaf abscission in deciduous trees, for example, is associated with short photoperiods. Also, temperature, moisture, and mineral supply have all been noted to influence the abscission process. Environmental factors appear to act through their effects on the synthesis, utilization and/or depletion of nutrient substrates and hormones within the plant. Addicott (2) recently reviewed the evidence pointing to the fact that, in addition to hormones, soluble nutrients are important regulatory factors of abscission. They serve as substrates for synthesis of the hormones and are involved in the maintenance of chemical equilibria within the plant.

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

‘Kerman’ pistachio trees produced incompletely developed leaflets and leaves with a reduced number of leaflets following the mildest winter in 48 years in California. Nuts were produced both laterally and terminally on current season’s shoots in addition to their normal production laterally on 1-year-old wood.

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

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

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

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

In contrast to other fruit tree species that produce flower buds in limited quantity at the same time a heavy crop is being produced, the pistachio (Pistacia vera L.) produces abundant inflorescence buds which, for the most part, abscise during the summer. Thus, alternate bearing in the pistachio is effected by a unique mechanism. Evidence is presented which suggests that the abscission of the inflorescence buds is the result of assimilate depletion when a heavy crop is produced.

Open Access