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Rooting and growth of Verbena cuttings (Verbena × hybrids Voss) were measured to determine response to foliar-applied benzylaminopurine (BA). There was no rooting response to BA application when visible nodal roots were present at the base of the cutting. There was no response to 30, 100, or 300 mg BA/liter applied to the foliage 48 or 96 hours after excision from the stock plant. Rooting-zone dry mass, total cutting dry mass, and number of roots were increased by 30 mg BA/liter applied immediately after excision when there were no visible nodal roots at the base of the cuttings. Foliar application of BA at 10 or 30 mg·liter-1 increased lateral bud elongation of subsequently rooted shoots by 20% and 49%, respectively. Application of BA during cutting propagation to enhance subsequent lateral bud elongation does not appear to inhibit rooting in Verbena stem cuttings. Chemical name used: 6-benzylaminopurine (BA).

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The difference between night and day temperature (DIF = day - night temperature) has been shown to affect plant height. A positive DIF (+DIF), cooler night than day temperature, increases stem elongation while a negative DIF (- DIF), warmer night than day temperature, decreases stem elongation. The physiological mechanism underlying the growth response to DIF is not understood, however, and the effects of day/night temperature differentials on root permeability to water and root elongation rate have not been studied. The objective of this study was to describe how +DIF and -DIF temperature regimes affect leaf water relations, root water flux (Jv ), root hydraulic conductivity (Lp ), and root elongation rates of `Boaldi' chrysanthemum [Dendranthema ×grandiflora Kitam. `Boaldi' (syn. Chrysanthemum ×morifolium Ramat.)] plants over time. Leaf turgor pressure (ψp) was 0.1 to 0.2 MPa higher in plants grown in a +6 °C DIF environment throughout both the light and dark periods, relative to those in a -6 °C DIF environment. Jv differed markedly in roots of plants grown in +DIF vs. -DIF environments. Rhythmic diurnal patterns of Jv were observed in all DIF treatments, but the relative timing of flux minima and maxima differed among treatments. Plants grown in positive DIF regimes exhibited maximum root flux at the beginning of the light period, while those in negative DIF environments had maximum root flux during the first few hours of the dark period. Plants grown in +DIF had significantly higher Lp than -DIF plants. Plants grown in +DIF and -DIF environments showed differences in the diurnal rhythm of root elongation. During the dark period, +DIF plants exhibited minimal root elongation rates, while -DIF plants exhibited maximal rates. During the light period, the converse was observed. In -DIF temperature regimes, periods of rapid root elongation coincided with periods of high Jv . Results of this study suggest that negative DIF environments lead to leaf turgor reductions and markedly alter diurnal patterns of root elongation. These changes may, in turn, act to reduce stem elongation.

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Abstract

Root promotion and root inhibition were measured for geranium and poinsettia cuttings during and after treatment at medium temp of 5 to 35°C at 5°C increments for 1 to 5 days. Optimum root initiation and elongation temp from 1 day of treatment were 15 to 30°C with reduced root initiation after 5 and 35°C and inhibition of root elongation after 5, 10 and 35°C treatments. Medium treatments for 3 or 5 days at 25 and 30°C increased root initiation and elongation which continued at accelerated rates during a 5 day period following treatment. Medium temp 5, 10, 15, and 35°C for 3 or 5 days reduced root initiation and elongation during treatment, and inhibition continued after treatments of 5, 10, and 35°C. Roots became brown for both species during 35°C treatment, while roots at 25°C and below remained white. After treatment root tip vascular and cortical cells varied in size but were anatomically similar. Distances from the root tips to the 1st xylem element were largest at 25°C allowing more cortical cells in the meristematic region.

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Plants, which move directly from the wild into commercial propagation, without the benefit of extensive breeding and selection, often pose production-oriented problems for growers. Vigorous plant growth, especially during the propagation phase of production is a common problem. The purpose of this work was to determine the degree of efficacy offered by chemical control of stem elongation in propagation of Porter Weed [Stachytarpheta mutabilis, S. mutabilis var. violacea, and S. urticifolia]. Tip cuttings of three Stachytarpheta species were given a 10-s dip in the following treatment solutions: daminozide (2500 and 5000 mg·L-1), daminozide and chlormequat chloride tank mix (2000 mg·L-1 ea.), paclobutrazol (2 and 4 mg·L-1), uniconazole (2 and 4 mg·L-1), distilled water, and undipped controls. Cuttings were then treated with a 0.1% IBA rooting powder and placed under intermittent mist on the propagation bench. After 2 weeks in propagation, cuttings were harvested and shoot elongation, root development, and dry weights were evaluated. The interaction of chemical and species was significant for stem elongation and dry weight; chemical effect on root development was also significant. Paclobutrazol and uniconazole offered greater control of stem elongation than daminozide, daminozide-chlormequat chloride, water, or control treatments.

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Tap roots of two coarse rooted species, Nyssa sylvatica and Quercus acutissima, were subjected to six treatment materials which were cut to fit or placed on the bottom of a 7.61 container. Each treatment material (paint only, Styrofoam plug tray, 3M floor buffer mat, peat fiber sheet, stone and weed barrier fabric) was either painted with Spin Out™ of impregnated with Spin Out™ WP. Treatments that allowed the tap root to penetrate the material, i.e. weed barrier fabric, stone and 3M floor buffing mat, were more effective in controlling tap root elongation. The weed barrier fabric significantly reduced tap root length of Quercus acutissima and Nyssa sylvatica by 80% and 67% respectively compared to controls and by 65% and 53% respectively compared to the paint only treatment. In some cases the 3M and stone treatments were more effective than the weed barrier fabric but were impractical because of weight or expense.

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Rapid and timely production of kiwi (Actinidia deliciosa) seedlings is often hampered by poor and erratic seed germination. This investigation was conducted to assess the effect of gibberellic acid, cold stratification (5° C), and their combinations on seed germination and subsequent radicle elongation. Germination counts and radicle elongation measurements were made two weeks after incubation at 25.4° C under continuous light and approximately 100% RH. GA treatments broke dormancy and increased germination and radicle elongation with increasing concentration up to 2500 ppm. At 5000 ppm, germination and radicle elongation were reduced. Cold stratification (1 and 2 week durations) alone did not affect germination nor break dormancy. Combined cold stratification and GA treatments significantly enhanced seed germination and radicle elongation with the best response at the highest GA concentration (5000 ppm) and longest stratification (2 weeks), regardless of whether the seeds were stratified prior to or after GA treatments.

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Attempts to improve somatic embryogenesis of five pecan (Carya illinoinensis L.) cultivars using different levels of blue-green aIgal extract added to the media proved effective. WPM4-pecan media, containing 1.0 g malic hydrozide/liter and 30 g sucrose/liter, for embryo enlargement showed that the higher the extract concentration the longer the embryo harvested after 7 to 8 weeks of incubation at 22 to 25C. `Desirable' responded the best to the algal extract, where the percent elongation recorded was 129.1, 177.3, 174.2, and 200.6 for 0%, 1%, 2%, and 4%, respectively. Dessicating the embryos at 5C for 5 days enhanced the conversion on WPM4 conversion media containing silver nitrate and GA3. The number of normal shoots and roots was higher at 1% extract in cultivars Muhan, Elliot, and S-17, while the 4% algal extract was more effective for `Desirable' and `Shawnee'. Algal extract had no effect on media pH. Survival of converted embryos in the greenhouse was promising.

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. Measurements. In an effort to gauge the extent and impact of tissue desiccation and root-ball damage on first-year twig elongation of transplanted nursery stock, plant water status, mechanical shock, and elongation were measured. Water stress for each tree was

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al., 2006 ). In addition, solution culture could remove border cells and mucilages that possibly protect root tips from Al toxicity ( Miyasaka and Hawes, 2001 ). Relative root growth, which is a measure of root elongation inhibition, can be used as an

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