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perspectives have been comparatively less explored. Our research explored this side of the carbohydrate network by using a cytokinin (CK), boron (B)–molybdenum-based product that aims to strengthen the plant’s source-to-sink relationship and assess whether

Open Access

Abstract

Seeds of table beet (Beta vulgaris L.) were soaked in either water or a 1% (v/v) solution of a seaweed extract prepared from members of species within the families Laminariaceae and Fucaceae (Cytex) prior to germination at 10°, 15°, 20°, 25°, and 30°C. Germination of the seaweed extract-treated seeds was superior to that of the water controls at all temperatures except 25°. Promotion of germination was attributed to the known cytokinin-like properties of the extract.

Open Access

The role of sucrose alone and in combination with different cytokinin-like compounds on the microtuberization of potato, Solanum tuberosum `Atlantic', was investigated. Single nodal segments were placed in Magenta boxes containing Murashige & Skoog medium supplemented with one of 15 treatments in a 3 × 5 factorial. Treatment factors were sucrose at 3%, 6%, or 9%, and cytokinin-like compounds at five levels [cytokinin-free; 2 mg kinetin/L; 0.1 mg thidiazuron (TDZ)/L; 1.0 mg AC 243,654/L; 0.1 mg AC 239,604/L]. Except in a few cases in kinetin and TDZ treatments, nearly all cytokinin treatments failed to induce tuberization at the 3% sucrose, noninductive level. However, all cytokinin treatments induced tuberization in the presence of 6% sucrose. By raising the sucrose level from 6% to 9%, more and larger microtubers were obtained in the cytokinin-free medium. At the 9% sucrose level, even though more tubers per box were produced by TDZ and AC 243,654 treatments, less total fresh weight of tubers per box resulted from kinetin, TDZ and AC 243,654 treatments because tubers formed were smaller. Higher sucrose concentrations (9%) favored tuberization in the cytokinin-free medium, whereas 6% sucrose was optimum for the medium containing cytokinins. Sucrose might produce a strong tuberization signal that might either change endogenous hormone levels affecting tuberization or activate a number of genes coding tuber proteins and enzymes related to starch synthesis.

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Abstract

Paper chromatography of coleus exudate extracts showed 2 regions of cytokinin activity detected by the radish cotyledon bioassay, one at Rf 0.1-0.3 and the other at Rf 0.6-0.8. Cytokinin activity was reduced (especially in Rf 0.1-0.3 region) by stress from low pH, low nutrition, low temperature, and by ethephon and chlormequat.

Open Access

Abstract

(2-chlorethyl)trimethylammonium Chloride (chlormequat) sprayed on tipped Clusters of girdled ‘Cardinal’ grape (Vitis vinifera L.) at 250 to 1000 ppm during bloom increased the number of seeded berries per Cluster but reduced berry weight Heavy Cluster thinning increased berry weight on chlormequat treated Clusters. Succinic acid-2,2-dimethylhydrazide (SADH) did not increase seeded berry set or affect any of the other fruit characteristics measured at the concentrations tested. The synthetic cytokinin, 6-(benzylamino)-9-(2-tetrahydropyranyl)-9H purine (PBA), resulted in a marked increase in seeded berries at 300 ppm, but the number of shot-berries was also increased.

Open Access

Abstract

A single preharvest spray of gibberellic acid (GA3), alone or with the cytokinin, isopentenyladenine (IPA), retarded leaf yellowing, and, to a lesser extent, leaf rot of romaine lettuce (Lactuca sativa L. ‘Hazera Yellow’). The most effective spray was 10 ppm GA3 plus 0.1 ppm IPA. Effects of 1 ppm GA3 together with 0.1 ppm IPA were similar to those of 25 ppm GA3 and were always superior to the controls (water-sprayed). Lettuce sprayed by the hormones and packed in polyethylene (PE) liners remained green and sound longer than that either sprayed or packaged.

Open Access

Six cultivars of potted rose (Rosa ×hybrida L.) plants were evaluated for shipping stress-induced leaf chlorosis during holding at 8, 16, or 28C for 2, 4, or 6 days. `Meijikatar' showed more leaf chlorosis than the similar `Meirutral' at the higher simulated shipping temperatures and longer durations. Plants of `Meijikatar' were treated before simulated shipping with BA, TZ, or Promalin at 0, 25, 50, or 100 mg cytokinin/liter each, then paper-sleeved and stored in the dark in fiberboard boxes at 16C for 5 days. Plant quality 5 days after removal from storage was better with BA at 50 or 100 than at 0 mg·liter–1. All cytokinin-treated plants showed less leaf chlorosis than controls. Benzyladenine at 50 or 100 mg·liter–1 reduced leaf chlorosis when compared to all TZ treatments. There were no differences among treatments in the number of etiolated shoots per plant. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (benzyladenine, BA); trans-zeatin (TZ); gibberellic acid (GA4+7) + BA (Promalin).

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Microshoots of `McIntosh' apple (Malus domestica Borkh.) were grown on Murashige-Skoog (MS) nutrient medium supplemented with either sucrose or sorbitol or with sucrose and an elevated level of cytokinin. Shoot growth was recorded and concentrations of fructose, glucose, sorbitol, and sucrose were analyzed in nutrient media and shoots during a 6-week subculture period. Axillary branching was stimulated by high cytokinin and sorbitol media, with increased biomass production and carbohydrate use on the high-BA medium only. The sucrose in the nutrient medium was hydrolyzed to fructose and glucose, which were equally taken up by shoots. Sorbitol was taken up somewhat less effectively. The elevated level of BA decreased sucrose hydrolysis in the nutrient medium. There were high concentrations of sorbitol in shoots grown on the sorbitol medium, and sorbitol also accumulated at the end of the culture period in shoots grown on sucrose. The amount of sucrose was low, and glucose was more abundant than fructose in microshoots. The starch content of leaves was not affected by treatments or sampling time. Chemical names used: N6-benzyladenine (BA).

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Abstract

The in vitro shoot proliferation responses of 4 Vitis genotypes in the presence of 3 cytokinins was examined. All genotypes grew best in media containing 6-benzyladenine (BA), but the concentration response was variable. Kinetin had no effect upon the 2 interspecific hybrid cultivars but evoked a slight response with 2 genotypes of V. labrusca and V. labruscana. Adenine sulfate had no effect alone; however, when combined with BA, it decreased the rate of shoot proliferation. Addition of the auxin picloram (PIC; 0.1–2.5 μm) to BA-containing (5.0–10.0 μm) medium reduced the rate of shoot proliferation. Using low concentrations of PIC combined with 0.0 or 1.0 μm BA, there was a small increase in shoot tip multiplication. Callus growth was rapid in the presence of 5–10 μm BA and 1–2.5 μm PIC. In summation, the rate of shoot proliferation in grape shoot tip cultures is governed to a large extent by the interaction of cytokinins and genotypes.

Open Access

Abstract

The formation of green islands in response to BA and zeatin application suggested that cytokinins were involved in the natural green island phenomenon of senescing apple leaves. The accelerated loss of chlorophyll and abscission of apple leaves following treatment with BA at 300 mg·liter–1 in both 1984 and 1985 resembled the symptoms of spotted tentiform leafminer (STLM) (Phyllonorycter blancardella F.) damage. The zeatin content of STLM-damaged leaves determined by HPLC was greater than that of undamaged leaves during the development of the third generation pre-adult STLM. The first generation STLM induced no change in zeatin levels of infested leaves. Chemical names used: N-(phenylmethyI)-1H-purine-6-amine (BA); (±-2-methyl-4-(1H-purine-6-ylamino)-2-buten-1-ol (zeatin).

Open Access