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James A. Wolpert and Louise Ferguson

Alternate bearing in pistachio (Pistacia vera L.) is correlated with crop load; a heavy crop on l-year-old wood appears to cause abscission of inflorescence buds on current wood. Defruiting heavily bearing trees before or during the period of nut growth stopped inflorescence bud loss. This relationship between crop and bud loss was affected by the fruiting status of neighboring shoots. Large defruited branches (> 5.5cm diameter). in fruiting trees had bud retention values (50% to 65%) equivalent to fully defruited control trees, but smaller branches showed reduced bud retention levels. Bud retention was increased 2- to 6-fold in small branches when neighboring branches were defruited. Nitrogen concentration of leaves in late August was positively correlated with the final bud retention percentage and inversely correlated with defruiting date.

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Hurriah H. Al-Juboory

Three node stem cuttings of Chrysanthemum `Fortune' were sprayed with Atrinal, 500, 1000, 1500 and 2000 ppm, to incipient runoff under greenhouse conditions. The results demonstrated that with higher levels of Atrinal, branch number, branch length, plant height, and flower number decreased in both unpinched and pinched plants. At the same time, the dry weight of both pinched and unpinched plants increased. Applications of Atrinal, 1000, 1500, and 2000 ppm, lengthened the number of days to flower by 40 days.

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E. Costes and Y. Guédon

The structure of 1-year-old trunks resulting from sylleptic branching are compared among apple (Malus domestica Borkh) cultivars with diverse branching and fruiting habits. The 1-year-old trunks developing from a graft are described as a succession of metamers whose structure refers to location, distribution, and length of sylleptic axillary shoots. We used a stochastic process called hidden semi-Markov chain to capture the embedded structure resulting from mixing of different types of axillary shoots developing along the trunks. The models, corresponding to the different cultivars, are composed of a first transient nonbranched state, a succession of transient states that cover the median sylleptic branching zone, and a final absorbing nonbranched state. They are interpreted with regard to complexity, extent, and branching distribution of the median sylleptic zone. Main results deal with the balance between long and short sylleptic shoots and the distribution of long sylleptic shoots along the trunks. Results suggest that sylleptic branching could be used as an early characteristic to evaluate the later branching behavior of cultivars.

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J. Phillip McKnight and G. L. Klingaman

Eighteen New Guinea impatiens cultivars were evaluated for performance as bedding plants and for suitability as hanging basket plants. The cultivars were treated with three growth retarding chemicals (B-9, Sumagic and Cutless) to determine their effect on plant growth, branching and overall flower development. Two applications of 2500 ppm B-9 produced the most commercially acceptable plants. Height and spread were reduced by approximately 30 percent with no reduction in the number of flowers produced or the number of days to bloom. Cutless and Sumagic applications reduced growth approximately 50 percent and delayed blooming as much as 2 weeks when compared to the untreated control. Growth regulator treatment had no effect on the number of branches produced except with Sumagic which resulted in an overall reduction in branching.

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Mark J. Bassett

The inheritance of two new induced mutations for spindly branch was investigated in common bean (Phaseolus vulgaris L.). Each mutant was found to be controlled by a recessive gene. Allelism tests were performed beween a previously reported spindly branch mutant (sb) and the two new spindly branch mutants; the new mutants were found to be nonallelic to sb and to each other. The gene symbols sb-2 and sb-3 are proposed for the new mutants. Repulsion phase F2 linkage tests were made for all nine combinations of reclining foliage (rf) and sb among the two mimic mutant series rf, rf-2, rf-3 and sb, sb-2, sb-3. No linkages were detected.

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Karim H. Al-Juboory and David J. Williams

Three node stem cuttings of Algerian Ivy Hedera canariensis were sprayed with growth regulators to incipient runoff under greenhouse conditions. The results demonstrated that the combination of BA + GA4+7, (Promalin) promoted branching of Algerian Ivy better than applications of BA or GA4+7 alone. Plants treated with Atrinal developed more shoots per node than those treated with GA4+7, BA, or Promalin. Increasing concentration of Atrinal from 0 to 3000 ppm, also reduced branch length and leaf number for both pinched and unpinched plants. 2,3,5—triodobenzoic acid (TIBA) significantly increased the branching of Algerian Ivy, although plant shape was not commercially acceptable due to epinasity of the foliage.

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Allen D. Owings and Steven E. Newman

Four rates of seven plant growth regulators were foliar-applied to 11.4 liter containers of Photinia × fraseri after initial root establishment. Growth regulators studied were uniconazole, paclobutrazol, dikegulac-sodium, ancymidol, 6-BA, GA4+7 and, 6-BA + GA4+7. Six months after application, plant height, plant width, growth index, and number of lateral and terminal branches were recorded.

Applications of uniconazole (30 mg a.i./liter), 6-BA alone or in combination with GA4+7, and dikegulacsodium stimulated lateral branching. The number of lateral branches increased linearly as paclobutrazol rates increased from 60 to 180 mg a.i./liter. Growth index decreased with increasing application rates of uniconazole and paclobutrazol, while the growth index of photinia treated with other growth regulators wasn't affected by application rate. Plant height was increased in GA4+7 treated plants.

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Tadeusz Jacyna

Branched (B) and unbranched (UB) one-year-old `Bradford'/`OHFx97' trees were examined at intervals between preparation for bare root harvest and long term storage to determine the extent of mechanical bud damage caused by the various handling steps.

After hand stripping of leaves, digging, transportation to the storage facility, and grading, and tying of bundles, there was a marked difference in the percentage of damaged buds between branched (26%) and unbranched (53%) trees. The B/UB live bud ratio before and after harvest was 1:0.45 and 1:0.26, respectively. This difference may have been due to a various morphological growth pattern which both types of trees had produced.

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Mogens Nicolaisen

Phytoplasma PoiBI is responsible for free branching in poinsettia (Euphorbia pulcherrima Wild. ex. Klotzsch). In this study, PoiBI was transmitted by dodder from poinsettia to crown-of-thorns (E. milii Des Moulins) in one out of ≈100 attempts, whereas grafting transmission was unsuccessful. PoiBI was shown to be viable in E. milii, as it was detected in the recipient plant and in its cuttings over 1.5 years by polymerase chain reaction. It was shown that PoiBI induces free branching in E. milii as well as in poinsettia. Smaller leaves, reduced growth rates, and delayed flowering were other effects of PoiBI infection.

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Muntubani D.S. Nzima, George C. Martin, and Chic Nishijima

We investigated the development of leaf area (LA) and the distribution of dry matter within branches of 25-year-old, alternate-bearing `Kerman' pistachio (Pistacia vera L.) trees that were in their natural “on” (heavy) or “off” (light) bearing cycles to determine the immediate and delayed effects of fruiting on shoot growth. Compared to “off” trees, individual leaves of “on” trees were greater in number and expanded twice as fast during the first 30 days after full bloom (FB) (FB + 30). Mature, fully expanded leaves of “on” trees were smaller (124.1±3.26 cm2) than those from “off” tree (163.3±3.40 cm2), indicating delayed demands of fruiting on initial leaf growth. Total LA per current shoot was greater in “on” than “off” trees because shoots of “on” trees averaged eight leaves, compared with six for “off” trees. More inflorescence buds per shoot (seven vs. three buds) abscised from “on” than from “off” trees. About 60% of the young developing nuts had abscised by FB + 30 when they weighed <250 mg each and another 25% abscised between FB + 30 and FB + 60 when individual nuts weighed ≈400 mg. The average total dry mass (DM) of individual branches of “on” trees increased 1322% (5·9 to 83·9 g) compared to 598% (4·2 to 29·3 g) in “off” trees. Besides nuts, leaves accumulated the greatest amount of dry matter within individual branches followed in decreasing order by current wood, 1-year-old wood, and inflorescence buds. DMs of individual leaves of “on” trees averaged between 15% and 48% greater than leaves of “off” trees. “Off” trees invested 4.6 g of dry matter into individual 1-year-old wood and 2.1 g into current wood. “On” trees, however, invested 1.3 g of dry matter into 1-year-old wood and 4.3 g of dry matter into current wood. One-year-old wood was an important major source of carbohydrates for developing leaves, current wood, rachises, and nuts. The immediate demands of fruiting on individual components of a branch were measured as losses in DMs. Individual leaves, current wood, 1-year wood, and rachises lost 1.1%, 0.3%, 1.1%, and 1.0%, respectively, of the average total DMs of individual branches of “on” trees. This loss was equivalent to 5.7%, 5.9%, 26.7%, and 16.4%, respectively, of the seasonal average peak DMs of the respective individual components of the branch.