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Abraham H. Halevy, Eitan Shlomo, and Ofra Ziv

Experiments aiming to adapt the perennial balloon flower (Platycodon grandiflorus) as a commercial cut flower crop were conducted for 4 years under various growing conditions: four controlled-temperature rooms at two photoperiods in a phytotron, heated and unheated greenhouses, and a saran net-house (15% shade). Best flower yield was obtained following crown cooling for 12 weeks at 2 to 4 °C. Platycodon is a day-neutral plant, but produce more flowering stems under long days. Flower initiation and development is enhanced with increased growing temperature from 17/12 °C (day/night) to 27/22 °C. At very high temperatures (32/24 °C), however, only a few flowers are formed. Best quality stems were produced at 12 to 14 °C night temperature. At higher night temperatures, flowering stems were thin and weak. Gibberellin treatments to the crowns and the plants did not affect flowering time. Chemical name used: gibberellin (GA3).

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Susan S. Han, Abraham H. Halevy, and Michael S. Reid

Vase life of individual flowers of cut brodiaea (Triteleia laxa Benth.) inflorescences ended 4 days after opening. Best vase life was achieved by harvesting inflorescences 1 to 2 days before anthesis of the first flower and holding them in a vase solution containing 2% sucrose and 200 ppm 8-hydroxyquinoline citrate (HQC). Such inflorescences had a display life of 12 days. Decreasing the pH of the vase solution or pulsing inflorescences with 10% sucrose for 16 hours did not increase their longevity. T. laxa flowers pretreated with 10% sucrose overnight could be stored for up to 2 weeks without significant reduction in vase life.

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Abraham H. Halevy, Menashe Levi, Menashe Cohen, and Vered Naor

Experiments to advance early production of herbaceous peony (Paeonia lactiflora Pall.) flowers were conducted over 8 years in the higher elevation, cooler regions of Israel. Anatomical studies during the summer revealed that flower bud initiation of apical buds in the crowns began at the end of July and continued also in lateral buds from mid-August until the plants became dormant in mid-November. Container-grown plants of various cultivars were moved to cold rooms maintained for 10 to 13 weeks at 2 °C, from mid-August to mid-October, then drenched with 250 mL of various concentrations of GA3 and transferred to a greenhouse. The optimal GA3 concentration for flower production was 100 mg·L-1. Plants treated in this way flowered 2-3 months before the natural flowering period. Field-grown plants in uncovered greenhouse structures were exposed to natural winter cold temperatures (0-10 °C), until they had received various chill units according to a “dynamic model” (for details see Erez et al., 1988). The crowns were then drenched with various amounts and concentrations of GA3, and the greenhouses were covered with plastic sheets. The optimal chill units for most cultivars was 40 and the optimal GA3 drench treatment was 250 mL of 100 mg·L-1. Covered and GA3-treated field-grown plants flowered ≈1 month earlier than untreated plants grown in the open field. The GA3 treatment also greatly increased the number of produced flowers.

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Susan S. Han, Abraham H. Halevy, and Michael S. Reid

Unpollinated brodiaea (Triteleia laxa Benth.; syn. Brodiaea laxa) flowers produced no measurable C2 H4 during their entire lives. Treatment with C2 H4 (0.03 μl·liter -1) induced senescence of open flowers, completely inhibited opening of buds and petal growth, and promoted ovary growth. Silver thiosulfate had no effect on flowers kept in air but counteracted the effects of applied C, H.. The effect of C2 H4 on ovary growth seems to be indirect, via promotion of petal senescence and mobilization of the petal's metabolites to the ovary. Brodiaea flowers are protandrous; the stigma appears to be receptive (as judged by a pollination-induced burst of ethylene synthesis) only when the petals start to senesce. At this stage, papillae on the stigma surface elongated and separated.

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Susan S. Han, Abraham H. Halevy, Roy M. Sachs, and Michael S. Reid

Exposure of dormant corms of Triteleia laxa `Queen Fabiola' to 20 ppm C2H4 for 7 days promoted flowering of small corms and resulted in increased apical meristem size, early sprouting, early flowering, more flowers per Inflorescence, and increased fresh weight of daughter corms and cormels. The respiration rate of the C&treated corms increased to four to five times that of the controls during the 7-day treatment, declined markedly after termination of the C2H4 treatment, but remained higher than that of the controls. The C2H4 effects were associated with increased growth rate and consequently a greater final size of the apical meristem (determined by scanning electron microscopy). Leaves produced by C2H4-treated corms were wider, longer, and weighed more than those of the controls.

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Susan S. Han, Abraham H. Halevy, Roy M. Sachs, and Michael S. Reid

Flowering of brodiaea (Triteleia laxa syn. Brodiaea laxa `Queen Fabiola') did not have an obligate requirement for manipulation of temperature or photoperiod. Vernalization of corms reduced the greenhouse forcing phase but did not alter the number of flowers per inflorescence or scape length. Long photoperiods hastened flowering but decreased flower quality and flowering percentage. Scape length, which was not affected by photoperiod or mother corm size, was increased when plants were grown at night temperatures < 10C. Diameter of the apical meristem in the dormant corm, flowering percentage, and flower quality were not affected by a 10-fold increase in corm size above a critical weight (0.6 g). In contrast, the weight and number of daughter corms were closely correlated with mother corm size. The optimum planting depth for brodiaea corms was 10 cm below the soil surface.