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  • Author or Editor: Dennis P. Stimart x
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The influence of root initiation medium pH on root formation was investigated in relation to uptake and metabolism of applied IBA in microcuttings of Malus ×domestica Borkh. `Gala' and `Triple Red Delicious'. Root formation and uptake of H 3-IBA were related inversely to root initiation medium pH. Maximum root count (10.3 roots) and IBA uptake were observed at pH 4.0. Regardless of pH, overall root count of `Gala' was higher (13.5 roots) than `Triple Red Delicious' (4 roots). Uptake of IBA was highest at pH 4.0 for `Gala' (1.7% uptake) and at pH 4 and 5 for `Triple Red Delicious' (0.75% uptake). Metabolism of IBA was the same regardless of root initiation medium pH or cultivar examined. One-half of the IBA taken up was converted to a compound that coeluted with IBAsp during high-performance liquid chromatography. Apparently, pH regulates root formation by affecting IBA uptake but not metabolism. The level of auxin in tissue appeared unrelated to root formation between genotypes. Chemical names used: 1H-indole-3-butyric acid (IBA); 5-H 3-indole-3-butyric acid (H 3-IBA); indole-3-butrylaspartic acid (IBAsp).

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Anatomical analysis was performed using a double-flowered mutant of Nicotiana alata Link & Otto. Flower doubleness resulted from petaloid modification of the androecium. Vascularized petal-like outgrowths arose from the anther, connective, and filament of the stamen. The vasculature in petaloid outgrowths from the anther and upper part of the filament originated from and was continuous with the vascular bundle of the filament. In contrast, the vascular bundles formed in the outgrowths from the lower part of the filament developed independently of the vascular bundle of the filament and were not connected to it at any time. Emergences consisting of epidermal and ground parenchyma tissue and lacking vascularization arose from the filament.

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Progeny of 158 F5 × F5 crosses of Antirrhinum majus (snapdragon) selected within and among cut flower postharvest longevity (PHL) categories (long = 12.6-16.8 days, middle = 9.3-12.1 days, and short = 4.8-8.9 days) were evaluated for PHL and quality traits. Results were compared with previous studies involving F2 × F2 progeny, and F3, F4, and F5 inbred lines. Heritability of PHL in F5 × F5 progeny (0.77 ± 0.11) agrees with that of inbred lines (0.79 to 0.81) but is higher than in F2 × F2 progeny (0.41). Therefore, selection for increased PHL should progress more rapidly and predictably through application of inbred lines rather than F2 individuals. Significant differences between F5 × F5 progeny PHL categories confirm PHL is heritable with a significant additive component. Heritabilities of quality traits in A. majus are high, suggesting selection for quality traits should progress without difficulty. Phenotypic and genotypic correlations of PHL with quality traits are not consistently significant across PHL studies in A. majus. Discrepancies between studies suggest most traits may not be correlated to PHL or are subject to strong environmental influence.

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Abstract

Seeds of 29 terrestrial orchid species representing 15 genera were surface sterilized by immersion in 0.5% sodium hypochlorite containing a wetting agent, washed, sown on a completely defined, semisolid embryo culture medium containing macro- and microelements, sucrose, amino acids, and vitamins, and incubated in the dark at 25°C. Six months after sowing, 16 species from 9 genera germinated and continued development while 13 species from 10 genera failed to germinate. Species of Cypripedium, Goodyera, Platanthera and Spiranthes differed in response in that one or more of each germinated and one or more did not. Seedling development was similar for most germinating species and progressed to the formation of a shoot or shoot initial in all but one. Apparently the mycorrhizal association thought to be required for terrestrial orchid seed germination and early seedling development can be replaced with aseptic culture on a completely defined medium for many terrestrial orchids.

Open Access

Abstract

Up to 50% of bulblets generated in vitro at 30°C from bulbscale explants of Lilium longiflorum ‘Ace’ produced an elongated axis in the 14 weeks after removal from tissue culture and potting in vermiculite. None of the ‘Ace’ bulblets produced in vitro at 25° and none of the ‘Nellie White’ bulblets produced in vitro at either 25° or 30° formed an elongated axis. Increased length of time that ‘Ace’ bulbs were stored at 4° before explanting as well as immersing bulblets generated in vitro at 30° in water at 45° for 1 hour before potting increased the percentage of bulblets with an elongated axis. Axis elongation was not related to bulblet size or to position of scale used for explanting (inner vs. outer bulb scale). Exposing ‘Ace’ bulblets generated at 30° to 3 or more weeks at 4° reduced the percentage of bulblets with an elongated axis to zero. Treatment of chilled bulblets for 2 hours in water at 45° did not reverse the effect of cold.

Open Access

Abstract

Changes in primary root number (RN), root dry weight (RDW), and shoot dry weight (SDW) on newly rooted stem cuttings of 7 woody ornamental plants were evaluated over 18 or 24 weeks after either no root removal or root removal where remaining RN equalled 25%, 50%, or 100% of the average RN at transplanting. Regardless of root removal treatment or season (February, June, or July), increases in primary RN occurred after transplanting and preceded increases in RDW and SDW. RDW and SDW increased progressively and together after primary RN ceased increasing. Cuttings started in February attained maximum RN in 12 to 18 weeks after transplanting, whereas those started in June and July required 6 weeks. Results suggest that stem cuttings of woody plants have a minimum, species dependent, primary RN which must be attained before measurable shoot growth is initiated.

Open Access

Anatomical events of adventitious root formation in response to root induction medium, observing changes during induction and post-induction stages, were made with microcuttings of `Gala' apples. Shoot explants on root induction medium containing water, 1.5 μm IBA, 44 mm sucrose, or 1.5 μm IBA + 44 mm sucrose after 4 days of treatment averaged 0, 0.2, 2.2, and 11.9 meristemoids per microcutting, respectively. Meristemoids formed in response to sucrose were confined to leaf gaps and traces. Time-course analysis of root induction with 1.5 μm IBA + 44 mm sucrose over 4 days revealed that some phloem parenchyma cells became densely cytoplasmic, having nuclei with prominent nucleoli within 1 day; meristematic activity in the phloem was widespread by 2 days; continued division of phloem parenchyma cells advanced into the cortex by 3 days; and that identifiable root primordia were present by 4 days. Cell division of pith, vascular cambium, and cortex did not lead to primordia formation. Meristematic activity was confined to the basal 1 mm of microcuttings. Time-course analysis of post-induction treatment revealed differentiation of distinct cell layers at the distal end of primordia by 1 day; primordia with a conical shape and several cell layers at the distal end by 2 to 3 days; roots with organized tissue systems emerging from the stem by 4 days; and numerous emerged roots by 6 days. Root initiation was detectable within 24 hours and completed by day 4 of the root induction treatment and involved only phloem parenchyma cells. Chemical names used: 1 H -indole3-butryic acid (IBA).

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Abstract

Plants of Rhipsalidopsis gaertneri [Regel] Moran ‘Crimson Giant’ were given continuous 14-hr long-days (LD), provided by 8-hr daylight plus 6-hr incandescent (Inc) irradiation; continuous 8-hr short-days (SD), provided by daylight; 2, 4, 6, or 8 weeks SD, then LD; or 2, 4, 6, 8 weeks LD, then SD. All plants receiving continuous LD or 2, 4, 6, or 8 weeks SD then LD flowered, whereas some or all plants in other photoperiod regimes failed to flower. Earliest and most prolific flowering occurred in response to 4, 6, or 8 weeks SD then LD. In a second experiment, plants previously given 8 weeks of 8-hr daylight (SD) were transferred to one of the following photoperiods: 12-, 14-, 16-, or 20-hr (8 hr daylight plus = to 12-hr Inc irradiation); 8-hr daylight plus 4-hr Inc night interruption (NI); or 8-hr daylight (SD). All plants receiving photoperiods of 12 to 20 hr or 4-hr NI flowered. Days from start of photoperiod treatments to visible flower buds was inversely related to duration of the Inc irradiation period, with a 4-hr NI comparable to 16-hr day. Days required for visible flower buds to complete development (flower expansion) were largely unaffected by duration or timing of Inc irradiation. Application of BA delayed flowering but more than doubled the number of flower buds per flowering apical phylloclade. Flower bud abortion was increased and both flower fresh weight and flower diameter were diminished by BA. Application of STS did not reduce flower bud abortion on BA-treated plants, but increased the percentage of apical phylloclades flowering. Chemical name used: N-(phenylmethyl)-lH-purin-6-amine (BA), silver thiosulfate (STS).

Open Access

Abstract

Cultivars of Zinnia elegans Jacq. were grown under long day (LD) photoperiods in the greenhouse in spring (Sp), summer (Su), fall (F), and winter (W) over 2 years to determine days from seed sowing to flowering (DTF), flower diameter (FD), height (H), node number below first inflorescence (NN), and the role of irradiance and temperature on DTF. All cultivars flowered earliest in Su, and latest in W. Cactus-flowered (cactus) cultivars (‘Carved Ivory’, ‘Rosy Future’, ‘Torch’) flowered later and were greater in H, FD, and NN compared to pompon cultivars (‘Cherry Ruffles’, ‘Pink Ruffles’, ‘Scarlet Ruffles’, ‘Yellow Ruffles’). The principal factor affecting DTF and NN was the season, whereas H and FD variation were due mainly to cultivar differences. Year X season interactions were significant for DTF, H, FD, and NN, but seasonal trends each year were similar. Mean daily temperature (MDT) from transplanting until flowering (DTFT) was lowest in W, highest in Su, and showed a linear correlation with DTFT for cactus (r = −0.89) and pompon (r = −0.92) cultivars. Mean daily photosynthetic photon flux (PPF) for DTFT was highest in Sp, followed by Su, F, and W due to greenhouse shading during Su and part of F; the relation between PPF and DTFT was described by a 2nd degree polynomial for cactus (r = −0.96) and pompon (r = −0.98) cultivars. DTFT was more a function of MDT than PPF for Sp, Su, and F crops, whereas late flowering of the W crop was due to lower MDT and PPF. Results demonstrate that Z. elegans can be accurately scheduled as a greenhouse crop on a year-round basis.

Open Access

Abstract

Leaf emergence from bulblets of Lilium longiflorum Thunb. generated in vitro from bulb-scale explants incubated in the dark at either 25 or 30°C was enhanced by 3 stimuli: incubation at 4°C for 1 or more weeks after removal from culture; immersion in water at 45° for 30 minutes to 8 hours after removal from culture; or in vitro red-light irradiation. For maximum response, bulblets generated at 25° required longer treatments at either 45° or under red-light irradiation. On the other hand, bulblets generated in vitro at 30° responded least to incubation at 4°. Although all 3 environmental factors ended dormancy, variation in rates of leaf emergence and total percentage of bulblets with leaves at the end of the experiments suggested differences in the state of bulblet dormancy due to in vitro temperature and differences in the physiological action of the environmental stimuli promoting leaf emergence.

Open Access