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  • Author or Editor: R. L. Stebbins x
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Abstract

The difficulty of photographing a large tree in an orchard so that its limb structure can be clearly seen without the distraction of a confusing background is familiar to many pomologists (Fig. 1). Even more frustrating is the problem of taking good slides of large trees for use in talks on pruning. Trees have a way of outgrowing whatever we stretch behind them in our attempts to simplify the background (Fig. 2). The use of flash photography at night enables one to photograph a large tree in a row of trees with little or no confusing background. The resulting negative can be used to make positive prints (Fig. 3) or can be projected as a slide (Fig. 4). Use of highly sensitive black-and-white film such as Kodak's Tri X, ASA 400, with which the accompanying photographs were taken, eliminates the need for an unusually powerful flash gun. Whether successfully photographed a whole tree with a 10 m spread from a distance of more than 10 m (Fig. 5). Fig. 4 is from a negative made from the original negative used to make Fig. 3. Fig. 4 shows how the original negative looks when projected as a slide for use with lectures on pruning.

Open Access

Abstract

Apple (Pyrus malus L.) seedlings or rooted layers growing in nutrient solution in the greenhouse were used to determine the role of xylem and phloem in the accumulation of Ca in the leaves. 45calcium accumulation increased with increasing rates of transpiration as measured by water losses. Girdling experiments demonstrated that the phloem was the primary route of translocation. Young leaves accumulated more 45ca than old leaves even though the water losses for plants bearing only young leaves or only old leaves were similar. 45calcium accumulation in mature leaves was decreased when the shoot tips were removed. Apparently, in young apple trees Ca moves primarily in the phloem, but leaks into the xylem at increasing reates in the younger stem and near the growing apex.

Open Access

Abstract

Boron sprays applied in the fall to ‘Italian’ prune trees (Prunus domestica L.) not deficient in boron resulted in a significant increase in fruit set and yield the following year. Analysis of midshoot leaf tissue the August following treatment showed no differences in boron content. These data indicate a possible transitory need for boron during the floral development and fruit set processes in ‘Italian’ prune which cannot be diagnosed by traditional leaf analysis.

Open Access

Abstract

Vesicular-arbuscular (VA) fungi from roots of apple (Malus domestica Borkh.) and soil from apple orchards in Oregon included Gigaspora margarita Becker & Hall, Glomus fasciculatum (Thaxter sensu Gerdemann) Gerd. & Trappe, and Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe. G. mosseae was the most competitive species in colonizing apple roots in certain Oregon orchards, based on spore identification. Other mycorrhizal fungi were identified in soils in which apples were growing.

Open Access

Abstract

Single crystals and clusters of crystals or druses found by polarized light microscopy in tissues of Pyrus malus L. cv. Jonathan were found to contain Ca using the electron microprobe. Crystals insoluble in 20% acetic acid occurred in cells adjacent to the vascular tissues near the pedicel in mature fruit and in dormant flower buds, stems, petioles, shoot apex, roots and callus tissue. Because of deposition of calcium as crystals, calcium supplies to cortical cells of apple fruit may be limited and may result in an increased incidence of internal breakdown due to low Ca levels in those cells.

Open Access

Abstract

Mycorrhizal fungal inoculation of seedlings of apple (Malus domestica Borkh.) substituted for P application in soils deficient in P. Of 3 mycorrhizal species, Gigaspora margarita Becker & Hall was the least effective in promoting plant growth, Glomus fasciculatum (Thaxter sensu Gerdemann) Gerd. & Trappe was the most effective, and Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe was intermediate. Combining the 3 species was no more effective than G. fasciculatum alone. VA mycorrhizae increased leaf P concentration in apple leaves from 0.04% to 0.19% on Parkdale soil which had an exchangeable P content of 13 ppm.

Open Access

Abstract

A pre- or postharvest foliar B application was found to increase fruit set of ‘Italian’ prune (Prunus domestica L.). A prebloom B spray failed to increase set. Neither fall nor spring applications influenced the amount of fruit lost in the midsummer or “blue” drop. All trees involved in the experiment had adequate B by the standard index of tree nutrition, August mid-shoot leaf analysis. Incipient B deficiency did not appear to be involved.

Fall foliar B increased B levels in dormant bud and spur tissues and in flower buds and flowers. A prebloom B spray increased B levels of floral tissues to a lesser degree. The highest B concentration was found in the ovary. Boron concentration in flower buds in April following a fall B spray was as much as five times the amount found in mid-shoot leaves in August. August mid-shoot leaf analysis revealed higher levels in leaves from trees treated the previous fall in only one of the 2 years.

Several morphological and physiological effects of the fall B spray were observed. Among these were a slight delay in the time of bud break, a decrease in the size of flower buds and mature flowers accompanied by reduction of style and pedicel length, and a decrease in pollen germinability. B level of pistil and pollen had no effect on in vivo pollen tube growth rate.

Open Access