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Open access

R. D. Heins and H. F. Wilkins

Abstract

Irradiating the all-green Chlorophytum comosum Thunb. with incandescent or red cellophane wrapped fluorescent lamps during the night increased the mean number of stolons formed per plant. A night interruption was more effective in stimulating stolon formation than irradiating the plants prior to sunrise or at sunset. There were no significant differences in stolon numbers formed between the two light sources within an irradiation treatment. Less and less time was required between the advent of subsequent stolons under all treatments during the 25 week experiment. Photoperiod treatments had no effect on time from visible stolons to anthesis. Plants in all treatments formed stolons and flowered.

Open access

S. M. Roh and H. F. Wilkins

Abstract

‘Ace’ lilies were placed in growth chambers at the visible flower bud stage under a 12-hour photoperiod with all possible day and night temperature combinations of 15.6°, 21.1°, 26.7°, and 32.2°C. At a constant day and night temperature of 15.6°, 21.1°, 26.7°, and 32.2° the time to flowering was 50, 28, 25, and 24 days, respectively. At a day temperature of 21.1°, night temperatures above 21.1° had little effect on flowering, but 15.6° greatly retarded flowering.

Open access

W. E. Healy and H. F. Wilkins

Abstract

When Alstroemeria ‘Regina’ plants were programmed to flower after 6 or 8 weeks at 5°C treatments, flowering was hastened by forcing plants at 18° vs. 13° greenhouse night air temperature. However, the 18° forcing temperature reduced flower production, flowers per shoot and shoot grade when compared to 13° forcing temperatures. Due to the decrease in flower production observed at 18° forcing temperature, a 13° temperature is recommended. When plants were grown for 16 weeks at 13°, an inductive temperature, or for 16 weeks at 21°, a non-inductive temperature, prior to the 5° inductive treatments, the 13° pretreatment without a 5° treatment was as effective as 8 weeks at 5° following the initial 21° pretreatment when forced at 18°. Thus, the cold requirement can be fulfilled either at 5° for a short period of time (6 to 8 weeks) or at 13° over an extended time span (16 weeks). Total shoot production during the flowering span decreased as the duration of the 5° treatment increased.

Open access

W. C. Lin and H. F. Wilkins

Abstract

Lilium longiflorum Thunb. cv. Nellie White bulbs were shipped in 1969, 1970, and 1971 from the west coast to St. Paul by air freight from July to October at 15 day intervals. Bulbs were given 0 or 2 weeks of 10°C, 15.5°C or 21 °C followed by 0 or 6 weeks of 4.5°C. Two weeks exposure to 10°C enhanced shoot emergence and flowering of late-harvested non-cooled bulbs and enhanced flowering of cooled bulbs. Treatments of 15.5°C or 21°C had little influence on shoot emergence and flowering of non-cooled bulbs and delayed flowering of early harvested cooled bulbs. With time and with increased bulb growth the degree of dormancy (delay of emergence) decreased and degree of maturity (enhancement of early flowering by 4.5°) increased.

Free access

H.F. Wilkins, W.E. Healy, and K.L. Grueber

For chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura], the hypothesis that a 12-hr 5C or 13C dark treatment could be used in conjunction with a 12-hr 27, 21, 17, or 13C light treatment for rapid flowering when applied during certain developmental stages was valid. Flowering of `Bright Golden Anne', planted on 23 Sept., was not delayed by 12-hr light/12-hr dark growth chamber treatments of 21/5C or 27/13C (day/night) if treated from planting (P) of the rooted cutting to the start of short days (SD), 3 weeks after start of SD to visible bud (VB) (SD + 3 to VB), or from VB to flower (F) when compared to the glasshouse control plants grown at 21/18C. Plants responded similarly if grown at 13/13C or 21/21C, but flowering was delayed compared to the 17/17C glass house control. Delays were absent, however, when 13/13C was used from P to SD, SD + 3 to VB, or when 17/13 or 21/13C was used from VB to F.

Open access

Terry L. Gilbertson-Ferriss and H. F. Wilkins

Abstract

Flowering dates of freesias (Freesia hybrida Bailey) sown at monthly intervals varied according to monthly temperature fluctuations over a 2-year period. Seeds germinated from April to June reached anthesis from December to March. April through June seeding dates were acceptable for obtaining optimal flower production and quality in Minnesota, but these plants were slower to flower than those seeded from July through November. Night interruptions by incandescent light hastened flowering, but flower quality was poorer than from plants grown under natural days. Short days and night interruptions using BCJ-Ruby incandescent lamps had no influence on flowering date.

Open access

T. Gilbertson-Ferriss, H. F. Wilkins, and Randy Hoberg

Abstract

Plants of Freesia hybrida Bailey ‘Moya’, grown from corms and ‘Royal Crown’ from seed flowered when the temperature was 13°C continuously or with 13° during an 8 hour light span or with 13° during a 16 hour dark span both of which were alternated with 24°. Flower quality was poor but marketable on plants treated a 13° light or dark temperature alternated with 24°. Results suggest that the commercial production season could be extended into warm seasons by maintaining 8 hours of inductive temperature (13°) in greenhouses or coolers. Flowering or corm filling did not occur at continuous 24°.

Open access

P. Gavinlertvatana, P. E. Read, and H. F. Wilkins

Abstract

Pretreatment of excised leaves of Petunia hybrida L. with AgNO3 permitted shoot formation equal to the control, when explants were cultured on a medium containing 6-benzylamino purine (BA), but increased callus formation, chlorophyll content, and ethylene production. When explants were cultured on a medium containing α-naphthaleneacetic acid (NAA), pretreatment with AgNO3 promoted callus growth, root formation and extension, and ethylene production, but inhibited root hair formation. Pretreatment of explants with CuSO4 suppressed ethylene production and chlorophyll content. Inclusion of AgNO3 partially overcame the effects of CuSO4 alone. When the rhizobitoxine analog, L-2-amino-4-(2-aminoethoxy)-trans-3-butenoic acid (Rh), was used for pretreatment, ethylene emanation was inhibited for 2 or 3 weeks. Number of shoots and roots, root length, root hair and callus formation were not affected by Rh except that callus growth was reduced on a medium containing NAA. NAA (1.0 mg/liter) promoted callus and root formation and induced high levels of ethylene, while kinetin (0.2 mg/liter) stimulated shoot formation but simultaneously induced much lower levels of ethylene.

Open access

H. Brent Pemberton and Harold F. Wilkins

Abstract

Florida-produced ‘Prize’ azalea plants were shipped to Minnesota with apical floral buds whose individual flowers had styles which had commenced elongating. These plants were ready for rapid forcing if given the traditional 6 weeks at 9°C. However, a single 2000 ppm GA (Pro Gibb3) spray treatment resulted in plants which flowered more rapidly without a traditional cold treatment when forced in a glasshouse under natural daylength (ND) in Minnesota during the spring and summer. Length of the ND in these experiments was considered critical, as plants forced in the spring and summer under an 8-hr short day (SD) treatment did not flower in a uniform manner, or floral abortion occurred in GA treated, uncooled plants forced during the autumn. Under ND conditions, extended to 20-hr by high pressure sodium, cool-white fluorescent or incandescent lamps, plants flowered more rapidly than those plants cooled at 9° for 6 weeks and forced under ND. Uniformity of flowering was enhanced and GA treatment had no effect when 3 weeks of 9° cooling preceded supplemental lighting treatments during autumn forcing. During winter, 20-hr of high pressure sodium + GA treatment or a SD treatment of noncooled plants resulted in more rapid, but similarly uniform flowering, when compared to plants with 6 weeks of cold treatment. These data provide evidence indicating that ‘Prize’ azalea floral buds may not exhibit a physiological dormancy.

Open access

W. E. Healy and H. F. Wilkins

Abstract

When Alstroemeria ‘Regina’ shoots were grown in a continuous 13°C air temperature, and the underground structures (rhizomes and roots) were placed in a 5°, 10°, 15°, 20°, or 25° water bath, plants produced 22%, 33%, 13%, 14%, or 5% generative shoots, respectively (Expt. 1). When the underground structures were grown at 13°, there were no differences in percentages of generative shoots, regardless if shoots were in a 13° or 21° air temperature, and regardless if shoots were under short or long photoperiods. When soil temperature was 21° and air temperature was 13°, 12% generative shoots were produced only with a night interruption photoperiod (Expt. 2). Data from these 2 experiments led us to conclude that floral induction was controlled primarily by temperatures to which the underground structures were subjected, regardless of the air temperature or photoperiod. Storage root and rhizome dry weights were promoted by 13° air, 13° soil temperatures and night interruptions with incandescent light. Treatments which had a high percentage of generative shoots also had high root and rhizome dry weights.