Search Results

You are looking at 1 - 10 of 26 items for :

  • Author or Editor: Dennis P. Stimart x
  • Journal of the American Society for Horticultural Science x
Clear All Modify Search

Abstract

Axillary shoot growth on scions of poinsettia (Euphorbia pulcherrima Wild, ex Klotz) was regulated by grafting nonbranching (‘C-1’) and self-branching (‘Amy’, ‘Glory’, ‘Super Rochford’) cultivars on each other. Branching of ‘C-1’ was increased when scions were grafted onto self-branching rootstocks and branching was decreased on self-branching cultivars grafted onto ‘C-1’ rootstocks. Initiation of axillary bud growth was promoted on younger nodes of ‘C-1’ when grafted onto self-branching rootstocks. Increased branching propensity of ‘C-1’ scions grafted onto rootstocks of self-branching types continued even after vegetative cuttings were rooted. Axillary bud activity was unaffected by leaf removal. Results suggest that axillary bud activity is governed by shoot and root interactions of the plant and that axillary shoot growth is governed by some endogenous factors translocated from the roots across the graft union to the shoot.

Open Access

Involvement of pH and IBA on adventitious root initiation was investigated with Malus domestica Borkh. microcuttings. The pH of unbuffered root initiation medium (RIM) increased from 5.6 to 7 within 2 days. Buffering with 2[N-morpholino] ethanesulfonic acid (MES) adjusted to specific pHs with potassium hydroxide prevented pH changes and resulted in a 2-fold higher root count at pH 5.5 compared to pH 7 or unbuffered medium. As pH decreased, lower concentrations of IBA were required to increase root counts. Colorimetric measurement of IBA in buffered RIM showed greater IBA loss and higher root count were associated with lower pH levels in all cultivars. This suggests that IBA loss from RIM depends on medium pH, which affects root count. Root count differences between easy-to-root through difficult-to-root cultivars were not consistent with amount of IBA loss from RIM. Cultivar differences in root count could not be explained solely by IBA loss from RIM.

Free access

We investigated the role of ethylene on adventitious rooting of `Gala' (easy-to-root) and `Triple Red Delicious' (difficult-to-root) apple (Malus domestica Borkh.) microcuttings. Root count increased significantly as IBA level increased, with highest root counts on `Gala'. Ethylene evolution increased significantly with IBA level without significant differences between cultivars. Basal section removal of microcuttings in the area of root origin reduced root count without changing ethylene evolution. Ethylene treatment of proliferated shoots before microcutting excision failed to enhance rooting. IBA-induced ethylene evolution was eliminated nearly by AVG, but root count remained IBA dependent. ACC reversed IBA plus AVG rooting inhibition, but ACC alone failed to influence root count. Polar auxin transport inhibitors NPA and TIBA stimulated ethylene evolution without increasing root count. Adventitious rooting of apple microcuttings was not associated with ethylene. Chemical names used: 1-H-indole-3-butyric acid (IBA); aminoethoxyvinylglycine (AVG); 1-aminocyclopropane-1-carboxylic acid (ACC); 2,3,5-triiodobenzoic acid (TIBA); N-1-naphthylphthalamic acid (NPA).

Free access

Evaluation of leaf stomatal numbers and postharvest water loss indicate these are important factors in Antirrhinum majus (snapdragon) cut flower postharvest longevity (PHL). Cut flowers with 9 days longer PHL had 53% fewer leaf stomata. Long PHL is associated with an early reduction in transpiration followed by low steady transpiration. Short-lived genotypes had a linear transpiration pattern over the period of PHL indicating poor stomatal control of water loss. Short-lived genotypes had 22% to 33% reductions in fourth quarter transpiration while long-lived genotypes had 2% to 8% reductions. In addition, short-lived genotypes had higher average fourth quarter cut flower weight losses compared to long-lived genotypes. Further investigation of stomatal numbers and functioning relative to PHL may provide breeders a rapid and nondestructive indirect selection method for PHL.

Free access

Lilium longiflorum Thunb. `Ace' bulblets generated in vitro at 25 or 30C were stored at 4C for O, 1, 2, 4, or 6 weeks after removal from culture and before planting to ascertain the effects of in vitro generation temperature and post-in vitro cold storage duration on bulblet growth responses during 36 weeks of greenhouse growth. Increasing post-in vitro storage duration decreased the number of days to first leaf emergence and percentage of plants producing shoots within 36 weeks, but increased the number of days to shoot emergence and anthesis, leaf number, and flower bud number. The length of time required for bulblet development from planting to shoot emergence was affected by storage duration more than periods from shoot emergence to visible bud and anthesis. It is feasible to produce high-quality L. longiflorum pot plants from in vitro-produced bulblets.

Free access

On-plant floret longevity and cutflower postharvest longevity (PHL) of Antirrhinum majus L., snapdragon, were evaluated using inbreds P1 (16 day PHL) and P2 (6 day PHL), F1 (P1 × P2), F2 (F1 self-pollinated), F2 × F2 (among and within PHL categories: long, 17 to 25 days; middle, 9 days; and short, 2 to 3 days), and F3 families (F2 self-pollinated). F2 on-plant floret longevity and PHL correlated to later generation PHL. Prediction of progeny PHL from F2 × F2 matings appears feasible if genotypic value for PHL of F2 is known. Selection for PHL is best based on evaluation of multiple cutflowers per genotype. Significant additive and dominant genetic variance components contribute to PHL.

Free access

Genetics of Antirrhinum majus L. (snapdragon) cut flower postharvest longevity (PHL) was investigated by generation means analysis using a white short-lived inbred (WS) and white long-lived inbred (WL) to determine mode of inheritance and heritability. Broad and narrow sense PHL heritability was estimated at 78% and 30%, respectively. Scaling tests for adequacy of an additive-dominance model in explaining PHL inheritance suggested absence of epistasis. However, joint scaling indicated digenic or higher order epistatic interactions. Fitting of a digenic epistatic model revealed significant additive effects and nonsignificant dominance and epistatic interactions. Additionally, based on sequential model fittings all six parameters [mean, additive (a), dominance (d), a×a, d×d, and a×d] proved necessary to explain observed PHL variation. Continuous variation for PHL observed in the F2 and backcross generations suggests PHL is quantitative. Assessment of associated traits revealed a positive relationship between number of flowers opening postharvest on a cut flower and PHL. In addition, floret wilting led to short PHL while floret browning was associated with long PHL.

Free access

Narrow-sense heritabilities and genetic correlations of ornamental quality traits of Antirrhinum majus (snapdragon) were evaluated with special reference to cut flower postharvest longevity (PHL). Inbreds P1 (16 days PHL) and P2 (3 days PHL) were hybridized to produce an F1 (P1 × P2) that was self-pollinated to produce an F2 population. The F2 were self-pollinated to produce F3 families and advanced through single-seed descent by self-pollination to the F5 generation. P1, P2, F1, F3, F4, and F5 were evaluated for ornamental quality traits. Quality traits were found to be quantitative and normally distributed. Narrow-sense heritability (h2) estimates were high and consistent across generations examined; PHL h2 ranged from 0.79 to 0.81 ± 0.06. Phenotypic and genotypic correlations revealed underlying physiological and pleiotropic interactions relevant to breeding programs aimed at simultaneous improvement of ornamental quality traits. PHL is inversely related to cut flower strength and days to flower, -0.44 ± 0.04 and -0.43 ± 0.44. Buds at discard is positively correlated to cut flower and plant diameter, cut flower weight and days to flower, 0.77 ± 0.05, 0.58 ± 0.06, 0.71 ± 0.06, and 0.77 ± 0.07, respectively. Gain from selection for quality traits of interest can be rapid.

Free access

Abstract

Zinnia elegans Jacq. ‘Carved Ivory’, ‘Cherry Ruffles’, and ‘Rosy Future’ were grown under short days (SD) or long days (LD) to determine the effect of photoperiod on flower initiation and morphological development. Plants grown under LD (14, 16, 18, or 24 hours) were greater in height, leaf size, flower diameter, and node number and flowered later compared to plants grown under SD (8, 10, or 12 hours). The greatest increases in plant responses occurred between 12- and 14-hour treatments. Supplemental irradiation (day continuation, night break, and predawn lighting) resulted in LD responses but did not equally affect days to flowering, stem diameter, or node number. Height and ray petal number were greatest for all cultivars under day continuation and flower diameter was largest under day continuation and predawn lighting. More LD before SD resulted in increases in height, stem and flower diameter, node number, ray petal number, and days to flowering, indicating a cumulative effect of LD on morphological development. Results demonstrate that Z. elegans is a facultative SD plant for floral initiation and development and that photoperiodic responses vary between genotypes.

Open Access

Abstract

Bulblets of Lilium longiflorum generated in vitro in the dark at 30°C produced leaves more rapidly and more completely after transplanting to vermiculite than those generated in vitro at 25°. The product of temperature × time (days) was equalized by varying the number of days at the 2 temperatures to make treatments comparable. Therefore, the effect of temperature in vitro was not due to a linear relationship between bulblet development and the product of temperature × time. Bulblets formed at 30°C for half of the temperature × time product of the tissue culture period produced leaves after transplanting at rates similar to those of bulblets generated at a constant 30°C. Exposure of bulblets generated in vitro at 25°C to 4° for 2 weeks before planting in vermiculite resulted in leaf production not significantly different from that of chilled or non-chilled bulblets generated in vitro at 30°C. However, chilling significantly increased fresh weight of bulblets produced in vitro at either temperature. The data suggest that temperature during in vitro development affects Easter lily bulblet dormancy as measured by leaf production.

Open Access