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  • Author or Editor: A. N. Roberts x
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Abstract

We determined origin and time required for development of callus and root initials in Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stem cuttings from stained sections. Callus originated principally from the vascular cambium, but phloem and xylem parenchyma also contributed. Continuous cell division, elongation, and differentiation within callus gave rise to root primordia. Once formed, root primordia elongated within 15–30 days.

There was no apparent difference in tissue origin of adventitious roots in stem cuttings collected from sheared juvenile or sheared or non-sheared adult trees during pre-, true, and post-dormancy. Time required for callus formation and root initiation varied with degree of bud dormancy. Rooting was low during pre-, almost none during true, and highest during post-dormancy.

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Abstract

Yearling ‘Nellie White’ Easter lily plants were subjected to various air and soil temperature combinations to determine temperature requirements for 6 growth phases, each of one-month duration. An air and soil temperature of 24°C favored rapid leaf unfolding, stem elongation, and flower expansion with concomitant depletion of primary scales. After flower buds were visible, soil temperature had no appreciable effect on their rate of expansion; air temperature was the controlling factor. Leaf unfolding rate, stem length, and flower bud size were of equal value in monitoring crop development. Secondary scale initiation and development during the prebloom period was positively related to soil temperature rather than air temperature and was maximum at 24°. The rate of scale initiation progressively decreased from first appearance of the secondary meristem until anthesis of the primary axis. High soil temperature decreased the diameter of the secondary (daughter) axis apical meristem at any time prior to appearance of flower buds on primary axis (buds visible).

Open Access

Abstract

An 18-hr photoperiod (LD) significantly increased cambial activity, rooting, bud respiration, and also hastened bud break of stem cuttings as compared with similar cuttings propagated under a 9-hr photoperiod (SD). Rooting response was modified by sampling date and temperature of the rooting medium. Rooting was least from August through November and greatest in December and January. Rooting temperatures of 18 and 26°C enhanced rooting without affecting bud activity.

Open Access
Authors: and

Abstract

Recent interest in the production of Rhododendrons as potted plants has raised many questions concerning propagation, dormancy, flower initiation, and general patterns of growth and development. Cathey (1) has shown that general growth habit may be altered to give a more compact plant through the use of Phosphon or by B-nine. He found further that flower initiation could be stimulated after the production of 4-5 flushes of growth instead of the normal 8-9 flushes required under natural conditions, thus making this plant useful as a potted plant. Myhre (3) showed that large applications of phosphate fertilizer increased the number of terminal apices initiating flowers in ‘Cynthia’. In 1920, work in the Netherlands by Luyten and Versluys (2) indicated that leaf and flower initiation occurred early in the growth cycle, May 31 to June 8.

Open Access

Abstract

The Nitrate Compensation Points (NCP) of 4 plum clones, Marianna 2624 (Prunus cerasifera Ehrh. × P. munsoniana Wight & Hedr.?), M-17 (P. cerasifera × P. munsoniana?), Myrobalan 3-J (P. cerasifera) and Myrobalan B. (P. cerasifera) were determined following NO 3 depletion from aerated nutrient solutions. Differences among NCP's were statistically significant; however, since the NCP's were low (ca. 5 μm NO 3 ) relative to the [ NO 3 ] of typical agricultural soils, the relevance to NO 3 uptake effectiveness under field conditions remains unresolved. Maximum NO 3 influx took place above 20 μm NO 3 , but 15 hour exposures to higher ambient [ NO 3 ] resulted in higher NCP's. Both decreased influx and increased efflux of NO 3 may have contributed to higher NCP.

Open Access

For about 30 years, the Univ. of California has used advanced laboratory techniques in addition to traditional methods to produce pathogen-free and true-to-type sweetpotato seedstock. The effort continues with the varieties important in the marketplace today. This program serves as a model for the use of meristem culture by foundation sweetpotato programs in other states.

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Abstract

Harvest date, bulb weight, and the number of scale and leaf primordia of the daughter axis of July-to-October-harvested bulbs of Lilium longiflorum Thunb. cvs. Croft, Ace and Nellie White were harvest maturity indices (HMI) evaluated as predictors of subsequent bulb responses to dormancy-removing and flower-forcing treatments. Higher HMI ratings associated with late harvest, e.g., increased bulb size and increased numbers of daughter leaf primordia, favored early shoot emergence and flowering with standard forcing programs. However, early-harvested bulbs with lower HMI ratings could be forced with equal or superior quality when given modified forcing regimes. Early-harvested bulbs without cold treatment were more responsive to long day (LD) flower induction than late-harvested bulbs. The optimum dormancy-removing temperature was always 15°C, but the flower-inducing optimum tended to shift from 10° to 5° with progressively later harvest. However, 10° storage favored earlier emergence, greater leaf and flower numbers, while total days to flower from potting remained the same at the 2 inductive temperatures. The interaction of bulb maturity at harvest and forcing regime emphasize the necessity of tailoring the forcing regime to the HMI of the bulb.

Open Access

Abstract

Succulent branch terminal cuttings of Douglas-fir [Pseudotsuga menziesii (Mirb) Franco] placed horizontally (adaxial side up) curved slightly. Cuttings placed vertically, horizontally (adaxial side down), or on a horizontal clinostat exhibited significant adaxial-convex curvature. The response is regulated, in part, by substances exported from the needles and terminal bud. Gibberellic acid (GA3), (2-chloro-ethyl)phosphoric acid (ethephon), amino-ethoxyvinylglycine (AVG), indolebutyric acid (IBA), triiodobenzoic acid (TIBA), and 6-benzylamino purine (BA) failed to affect the curvature of vertically placed shoots.

Open Access

Abstract

A study of shoot apex size and initiatory activity in August-harvested ‘Ace’ bulbs following 0, 6, and 18 weeks vernalization at 40°F showed negetative correlations between leaf and flower number and length of vernalization treatment, and between apex size and this cold treatment. Growth acceleration as reflected in earlier shoot emergence, internode elongation and rapid leaf unfolding was evident following 6 weeks’ 40°F storage, but prolonged (18 weeks) treatment drastically reduced subsequently initiatory activity and rate of leaf unfolding.

Open Access

Abstract

Inflorescence slices of tall bearded iris (Iris sp.) regenerated callus in vitro on a modified Murashige-Skoog high salt medium supplemented with 2.5 mg/liter napthaleneacetic acid (NAA) and 0.5 mg/liter kinetin. Callus pieces transferred to light initiated plantlets at their periphery and produced fuU-sized, true-to-type flowering plants when transplanted to soil.

Open Access