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Brian E. Corr and Richard E. Widmer

The influences of irradiance level, day length, temperature, and leaf area on growth and flowering of Zantedeschia elliottiana Engl. W. Wats (yellow calla lily) and Z. rehmannii (pink calla lily) were determined. Plants grown with 45% or 15% of natural irradiance were taller than those grown under full natural irradiance but flowered at the same time and produced a similar number of flowers. Leaf removal treatments had no effect on any characteristic measured. Plants grown with a night interruption (NI; 2200 hr to 0200 hr) were taller than those under short days (SD = 8 hours), but flowered at the same time and produced a similar number of flowers. Plants were grown with air at 15 or 20C in combination with medium temperatures at ambient level (1C less than air temperature) or a constant 20 or 25C. Z. rehmannii grown with the medium at 20 or 25C and air at 1.5 or 20C flowered faster and were taller than plants grown with air at 15C and with the medium at ambient temperature, but plants from all temperatures produced the same number of flowers over a 120-day cycle. When plants grown with a NI in the first cycle were replanted and grown through a second cycle, they were taller than plants grown from SD treatment first-cycle plants. No first growth-cycle treatment influenced flowering in the second growth cycle.

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Brian E. Corr and Richard E. Widmer

Growth and flowering of Zantedeschia elliottiana W. Wats. and Z. rehmannii Engl. were studied. Rhizomes of both species were produced either in a glasshouse or outdoors in California. Plants grown from glasshouse-produced rhizomes flowered within 90 days only when a preplant rhizome soak of 500 ppm GA, was applied. Control plants of both species flowered when grown from field-produced rhizomes, but a GA3 preplant rhizome soak significantly increased the number of flowers (spathe and spadix) produced. Paclobutrazol, applied as a preplant rhizome soak or as a soil drench when shoots were 2 to 3 cm long, significantly limited plant height of Z. rehmannii from either source if not treated with GA,. Paclobutrazol and GA, treatments interacted significantly to affect height and number of flowers of Z. rehmannii grown from field-produced rhizomes. Treatment with GA3 overcame the dwarfing effect of paclobutrazol, while paclobutrazol treatment limited flower production. Z. rehmannii rhizomes >6.5 cm in diameter produced more shoots and leaves than smaller rhizomes, regardless of GA3 treatment. Emergence, number of shoots, and number of leaves from Z. elliottiana were not significantly affected by the rhizome size-GA3 variable combination. Production of normal flowers was increased by GA3 treatment of all sizes of Z. rehmannii rhizomes except the smallest, with the most flowers being produced by plants from the largest rhizomes. Production of deformed flowers was greatest from rhizomes treated with 500 ppm GA3, with no deformed flowers on control plants.

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Neil O. Anderson, Peter D. Ascher, Richard E. Widmer and James J. Luby

The generation time (0.75 to 1.5 years) in perennial, hexaploid chrysanthemums [Dendranthema grandiflora Tzvelv. (Chrysanthemum morifolium Ramat.)] impedes the rate of progress for sexual breeding programs in creating new clonal cultivars, inbred lines for hybrid seed production, and genetic studies. Modifications to the crossing environment and embryo rescue were evaluated to minimize the chrysanthemum generation cycle. One greenhouse chrysanthemum clone was outcross-pollinated using a bulk pollen source. Following emasculation, inflorescences were either left in situ or the peduncle bases were placed in styrofoam boards floating on a solution of 1% sucrose and 200 ppm 8-HQC under laboratory conditions. Embryogenesis occurred at a faster rate under laboratory conditions as tested with histological techniques; the heart stage appeared as early as the second day after pollination, compared with 11 days using in situ methods. Total embryogenic development time ranged from 25 (laboratory seed development) to 52+ days (in situ ripening). In a second test, embryo rescue (ER) significantly improved percent seed set, percent germination, and percent of progeny reaching anthesis relative to normal development. ER progeny from both garden parents were significantly earlier in total generation time than corresponding non-ER siblings. Laboratory seed development and ER were then used sequentially to obtain an average progeny generation time of =100 days, thus allowing for three generations per year. The potential impact of these two techniques on breeding chrysanthemums and other perennial crops with long generation times is discussed.