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Abstract
Mobilization of carbohydrates to fruits of 2 genotypes of tomato (Lycopersicon esculentum Mill.) differing in total fruit solids content, LA 1563 (1563) and ‘VF145B-7879’ (‘7879’), was investigated. On the basis of 2 separate studies, fruits of 1563, the higher solids genotype, appeared to be stronger sinks for assimilates than fruits of ‘7879’. LA 1563 partitioned a significantly larger percentage of 14C to the fruits than ‘7879’. Fruits of 1563 took up more 14C-sucrose from agar medium than ‘7879’ fruits, both on the basis of total uptake and specific activity. Starch was found at higher levels in fruits of 1563 than in those of ‘7879’ from 10–30 days after anthesis. No starch was detectable in either genotype 50 days after anthesis. Fruit sucrose levels tended to be lower in 1563 than in ‘7879’ throughout fruit development. The possible physiological relationships between carbon metabolism and the rate of import of assimilates by fruits are discussed.
In a simple, yet elegant experiment conducted 30 years ago, Chan and Cain (1967) using 'Spencer Seedless', a facultatively parthenocarpic apple (Malus×domestica Borkh.) cultivar, proposed that seeds inhibited flowering and accentuated biennial bearing in apple. Their conclusions have been extrapolated widely to include apple and other species. We have tested the universality of their conclusions using 'Bartlett' pear (Pyrus communis L.), a commercially important, facultatively parthenocarpic cultivar. Unlike 'Spencer Seedless' apples and seedless 'Bartlett' pear grown in France, California-grown seedless 'Bartlett' pear fruit strongly inhibited flowering the following year. However, the presence of seeds increased 'Bartlett' pear fruit size relative to seedless fruit by 13% and 20% in nonthinned and heavily-thinned pear trees, respectively, indicating that seeds increased fruit sink strength.
Spurs are the primary bearing unit in mature `Nonpareil' almond (Prunus dulcis (Mill.) D.A. Webb) trees. Our objective was to determine whether almond spurs behave autonomously with respect to various biological activities throughout the season. If autonomous, a spur's carbohydrate demands are met primarily by its own leaves and, therefore, the sink to source ratio of the spur itself is expected to be closely linked to its growth and development. In these experiments almond spurs differing in leaf area and/or fruit number were monitored for leaf development, fruit set, floral initiation, spur survival and carbohydrate storage. Previous-season spur leaf area had no relation to the number of leaves preformed within the dormant vegetative bud or final spur leaf area in the current season, but spurs which fruited in the previous season began spring leaf expansion later and current-season spur fruiting was associated with lower spur leaf area. There was little or no relationship between final percentage fruit set at the spur level and spur leaf area in either the current or previous seasons. Current-season spur leaf area was positively related to both spur flower bud number and spur winter survival. Carbohydrate storage in dormant spurs increased with increasing previous-season spur leaf area. These data are consistent with the concept of spur autonomy especially with regards to spur activities late in the season. The relationships of some of these same spur parameters to spur light exposure are currently being investigated.
The effects of low and high crop loads in 2002 on floral development (Summer 2002), pistil size at anthesis (Spring 2003), and subsequent season fruit size at maturity (Summer 2003) were studied. Trees were all thinned to the same crop load in 2003. Three peach cultivars (Elegant Lady, O'Henry and Fairtime) with different ripening times (mid-July, mid-August, and early-September, respectively) were used to assess the effects of current season crop on floral development for the subsequent season. Based on previous literature, we reasoned that the maximum competition for carbohydrates between maturing fruit and developing buds is likely to occur at fruit maturity, especially under heavy crop loads. In 2003, individual fruit were harvested and weighed at maturity. In all three cultivars, a heavy crop load reduced the percentage of floral buds initiated and delayed floral differentiation. A heavy crop load also reduced pistil size at anthesis and fruit size at maturity in the subsequent season. These data support the practice of vigorous pruning to annually renew fruiting wood in peach to minimize the influence of crop in the previous season on the subsequent season's fruit and maintain large fruit sizes.
Abstract
Walnuts (Juglans regia L.) with and without (2-chloroethyl)phosphonic acid (ethephon) treatment were harvested at the earliest practical time and 3, 7, and 10 days later. With both treatments a delay in harvest resulted in kernels of lower quality and subsequent value. Furthermore, lower quality was found in earlier maturing than in later maturing walnuts when harvested from the same tree on the same day. In all comparisons kernels from ethephon-treated nuts were of higher value than controls. Walnuts left in the drier beyond the time necessary to remove excess moisture lost negligible quality and value.
Abstract
Major leaf alkanes (C29-C33) of 2 scions on 10 rootstocks of citrus were examined by gas chromatography. A small but definite effect of the rootstock on the alkane profiles of the scions was observed. The effect of rootstock on alkane patterns in juice sacs was very small. Rootstock affected the fatty acid patterns of total and neutral lipids as well as of triglycerides and sterol esters.
Abstract
Long-chain alkanes present in epicuticular wax of citrus leaves changed in composition as the leaves matured. From 89 to 95% of the hydrocarbons in the mature leaves were linear, saturated, and C29 to C33 compounds. Alkane profiles changed during the year but were not influenced by the period of leaf flush (spring or fall). The alkane profiles for 67 citrus cultivars, representing 11 citrus biotypes, were determined by gas liquid chromatography (GLC). The mean alkane profile of 9 of the bio types were distinct from the others as determined by Duncan's multiple range test, Twelve other citrus and related taxa were examined, and the profile of each showed possible inheritance patterns.
The commercially successful apple (Malus pumila Mill.) cultivar Honeycrisp is known for its high degrees of crispness and juiciness. This cultivar has been incorporated into numerous breeding programs in an effort to duplicate its desirable texture traits in conjunction with such other traits as reduced postharvest disorders, disease resistance, and improved tree vigor. This study characterizes variability and estimates heritability for several apple fruit texture traits within a large breeding population over several years. Five full-sib families, all sharing ‘Honeycrisp’ as a common parent, were assayed with respect to crispness, firmness, and juiciness using sensory evaluation panels and total work required to fracture tissue using instrumental methods. The incomplete block design of the sensory panels, coupled with best linear unbiased prediction, facilitated the evaluation of a large number of genotypes with small numbers of fruit per genotype while accounting for individual sensory panelist effects. Broad-sense heritability estimates exceeded 0.70 for all four traits. Principal component analysis, applied to the phenotypic data, characterized ‘Honeycrisp’ as having average crispness and low firmness (53rd percentile relative to its offspring) but also as being a relatively extreme example of high juiciness and low work to fracture (first percentile). The improved characterization of desired fruit texture phenotypes and the high levels of broad-sense heritability provide valuable tools for the further development of new, high-quality apple cultivars.
Although microwave-powered systems have been used for nearly two decades as UV sources for annealing and other industrial processes, recent discoveries indicate that these systems may also have application in providing a source of high intensity lighting. The spectral characteristics of newly developed microwave-powered lamps will be described in comparison to sunlight and a mixture of high pressure sodium and metal halide lamps. The responses of plants grown under these sources will be compared.
Abstract
The Nitrate Compensation Points (NCP) of 4 plum clones, Marianna 2624 (Prunus cerasifera Ehrh. × P. munsoniana Wight & Hedr.?), M-17 (P. cerasifera × P. munsoniana?), Myrobalan 3-J (P. cerasifera) and Myrobalan B. (P. cerasifera) were determined following