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- Author or Editor: Julian C. Crane x
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.
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.
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.
Abstract
Production of blank nuts in ‘Kerman’ pistachio was the result of both parthenocarpy and seed abortion, the latter being responsible for the major portion. The degree of parthenocarpy was relatively uniform throughout the entire tree population, but seed abortion varied according to the history of blank production of the individual trees. Production of blanks, therefore, appeared to be governed by the seedling rootstocks.
Abstract
Kernel dry weight and crude fat accumulation, as well as shell dehiscence and change in shell color, all indicated that the nut of pistachio (Pistacia vera L.) is physiologically mature at the time the hull separates easily from the shell. Harvesting prior to or after that critical point resulted in undeveloped kernels or in stained and unattractive shells, respectively. The data indicate that nuts of highest quality may be obtained by harvesting within a period of about one week.
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.
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.
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.
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.
Abstract
Neither abscisic acid (ABA) levels in developing kernels nor in the developing inflorescence buds themselves were found to be related to abscission of inflorescence buds and consequent alternate bearing in pistachio (Pistacia vera L.).