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Abstract

Extended long days or interrupted night photoperiods increased leaf number and top fresh weight, and decreased tuber formation compared with short days with 2 cultivars of the “NonStop” series of tuberous begonia (Begonia X tuberhybrida Voss). Short days increased tuber size and fresh weight and reduced top fresh weight of both cultivars. ‘Double Red’ showed greater leaf number, top fresh weight, tuber fresh weight, and tuber size at 22°C than at 26°, while ‘Double Orange’ showed only greater top fresh weight at 22°. Flowering was enhanced in both cultivars under long days.

Open Access

Abstract

Abstract. Astilbe X arendsii Arends ‘Avalanche’, ‘Deutschland’, ‘Fanal’, and ‘Red Sentinel’ were chilled for 0, 3, 6, 9, or 12 weeks at 5°C. Maximum flower number, height, and fresh weight occurred when plants were chilled for 12 weeks. No flowering occurred when ‘Avalanche’ or ‘Deutschland’ were chilled for less than 9 weeks or when ‘Fanal’ and ‘Red Sentinel’ were chilled for less than 6 weeks. ‘Fanal’ and ‘Red Sentinel’ grew significantly taller when forced under a 14-hour than under a 9-hour photoperiod.

Open Access

Abstract

West Indian mahogany [Swietenia mahagoni (L.) Jacq.] grown outdoors under 63% shade in southern Florida exhibited 3 distinct growth phases during the autumn and winter months. During the first phase (September through November), long-day conditions enhanced growth beyond that of natural daylength plants. In the 2nd phase (December through February), plants were essentially quiescent under both photoperiodic regimes in response to cool temperatures. In the 3rd phase (beginning in March), both long-day and natural daylength plants resumed growth at comparable rates. Thus, extending the photoperiod increases the growth rate in the autumn, but has little effect thereafter.

Open Access
Author:

Stratification by chilling is the primary factor controlling germination of brodiaea (Triteleia laxa Benth.) seeds. A minimum of 8 weeks of low temperature (3C) was required for maximum germination. Soaking seeds in a solution of 1000 mg ethepho/liter for 20 h reduced the number of weeks at low temperature required for germination. Cormel size was affected by the photoperiod during seedling growth. Long days induced early leaf senescence, and cormels harvested from seedlings grown under long days weighed only half as much as those grown under short days. Chemical name used: 2-chloroethyl phosphoric acid (ethephon).

Free access

Abstract

Cold temperature treatments stimulated inflorescence formation of Aguilegia × hybrida at the 12-leaf stage. Long photoperiods slightly advanced flowering further, but caused petiole elongation. Sprays of butanedioic acid mono-2,2-dimethylhydrazide (daminozide) at 2,000 mg/liter effectively prevented petiole elongation.

Open Access

Abstract

Bird-of-paradise plants of 2 clones were grown for 3 years under various environmental conditions. Flower production was 30–50% higher in plants grown at minimum night temperature of 13° than at 21°C. Shading (50%) reduced flowering in 1 clone. Photoperiod had no effect on flowering.

Open Access

Floral induction of 10 Hydrangea macrophylla (Thunb.) Ser. cultivars (`All Summer Beauty', `Dooley', `Endless Summer', `Générale Vicomtesse de Vibraye', `Lilacina', `Mariesii Variegata', `Mme. Emile Mouillère', `Nikko Blue', `Penny Mac', and `Veitchii') was evaluated to determine the remontant flowering potential. Cultivars exhibiting superior flowering potential could facilitate year-round production of florist s hydrangea and expand the geographic adaptation of hydrangeas in the landscape. Plants were tested under either 8-hour inductive short-day (SD) or 24-hour noninductive extended-day (ED) photoperiods at 24 ± 2 °C. Floral induction of H. macrophylla occurred under both SD and ED but was more rapid under SD than under ED. Shoot length and total number of nodes were significantly different for cultivars, photoperiods, and harvest dates. Significant differences in the floral initiation and development were observed among cultivars. `Penny Mac', `Endless Summer', `Lilacina', `Mme. Emile Mouillère', and `Nikko Blue' displayed significantly greater floral meristem development under SD than all other cultivars. Over the nine-week period, only `Dooley', `Endless Summer', and `Penny Mac' floral development was affected significantly greater by SD photoperiods than ED photoperiods. All others cultivars showed similar floral development under SD and ED. Stage of meristem development was highly correlated with number of nodes, but not with shoot length.

Free access

Abstract

Plants of 4 azalea cultivars which remained in a greenhouse with 18°C minimum temperature from last pinch through flowering and received 18-hour photoperiods (LD) following 6, 8, or 10 weeks of 9-hour photoperiods (SD) flowered 2 to 7 weeks earlier than plants cold-stored at 3°C for 5 weeks following 12 weeks of SD. Flowering of cvs. Red Wing, Alaska, and Gloria was hastened more by LD treatment than by 5 weekly applications of 1000 ppm gibberellic acid (GA3), whereas flowering of ‘Chimes’ was affected about equally by these 2 factors. Flowering was most uniform with cold-storage, but plants of all cultivars except ‘Chimes’ were well covered with flowers following all treatments. Percentage of flowers open at one time increased as SD exposure increased from 6 to 10 weeks and that of ‘Chimes’ was increased by GA3 treatment. Vegetative bypassing varied more among cultivars than among treatments. Pedicels of ‘Alaska’ and ‘Chimes’ flowers on plants with LD treatment without GA3 were shorter than those on cold-treated plants, whereas those with LD plus GA3 were longer. Succinic acid-2, 2-dimethylhydrazide (SADH) at 3000 ppm delayed flowering of non-cold-treated plants of ‘Red Wing’, ‘Alaska’, and ‘Gloria’.

Open Access

Abstract

Trifoliate orange [Poncirus trifoliata (L.) Raf.] and various other commonly-used rootstocks, submitted to long-day (LD) of 16 hours, (normal day + 4 hr incandescent light break), normal day (ND) of 12 hours ± 1 hr 10 min and short-day (SD) of 8 hour photoperiods fell into 2 groups—those which responded to LD tratment and those which did not. Rootstocks in the first group, Christianson, Beneke, Pomeroy, Rubidoux and Yamaguchi, trifoliate orange cultivars; Carrizo and Savage citranges [P. trifoliata × C. sinensis (L.) Osbeck.]; Sacaton citrumelo [P. trifoliata × C. paradisi Macf.]. Hawaiian sweet orange (C. sinensis) and Milam lemon (C. jambhiri Lush.), responded strongly to LD treatments in shoot growth and stem diameter. Rootstocks less responsive to photoperiod include Cleopatra mandarin (C. reshi Hort. ex Tan.), Estes lemon, (C. jambhiri), Troyer citrange, Swingle citrumelo, C. macrophylla Webster, C. taiwanica Tan. and Shin and C. volkameriana Pasq. This second group was considered better adapted to tropical conditions because they made better growth under SD conditions.

Open Access

The potential photoperiodic effects and interactions with temperature were identified for flowering of german primrose (Primula obconica). The german primrose `Libre Light Salmon' was grown at long days (LD, 16 hours) or short days (SD, 8 hours) and 61 or 68 °F (16 or 20 °C). Visible bud (VB, 2-mm flower buds) averaged 90 days from seeding for plants grown at 61 °F independent of photoperiod or at 68 °F under LD. At 68 °F and SD, VB was delayed and flowering (horizontal petals) had not been observed at termination of the study (146 days from seeding). Flowering averaged 111 days at LD and 68 °F, 122 days at LD and 61 °F, and 133 days at SD and 61 °F. When plants within each temperature were shifted at weekly intervals from one photoperiod to the other, increasing duration of initial SD resulted in slower VB and at 68 °F more than 8 weeks resulted in no flowering. Changing to SD from initial LD did not affect VB or flowering at either 61 °F or 68°F. These results suggest flowering of german primrose is faster under LD than SD at the recommended production temperatures of 65 to 68 °F (18 to 20 °C).

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