Controlling seedling height by treating seeds with plant growth regulators

Treating seeds with growth regulators may be a suitable method for controlling plug height of selected ornamental and horticultural plants. Soaking seeds in 50--1000 mg·L-1 paclobutrazol solutions reduced plug growth in verbena (Verbena x hybrida Voss., cv. Quartz White), pansy (Viola wittrockiana , cv. Bingo Yellow Blotch), salvia (Salvia splendens, cv. Vista Red), marigold (Tagetes patula L., cv. Bonanza Gold), dill (Anathemum graveolens, cv. Fernleaf), and cucumber (Cucumis sativus, cv. Poinsett 76SR). When treating seeds with growth regulators, seedling emergence was delayed and reduced in verbena, pansy, salvia, dill, but not cucumber or marigold. Osmopriming or coating verbena seeds with 10--500 mg·L-1 paclobutrazol were associated with 30--93% or 86--100% reduction in seedling emergence, respectively. Soaking marigold seeds during 0.15--45 min in 1--5 mg·L-1 uniconazole solutions resulted in plants which were shorter up to 23%, while similar application of 10--60 mg·L -1 ancymidol solutions resulted in plants which were shorter up to 6%. Soaking marigold seeds in 1--5 mg·L-1 uniconazole or 10-60 mg·L-1 ancymidol solutions did not reduce seedling emergence. Storing paclobutrazol-soaked seeds in a cold chamber for 22 months did not affect marigold growth reduction rates and seedling emergence. Soaking celosia (Celosia cristata, cv. New Look) seeds in 50--1000 mg·L-1 paclobutrazol solutions was associated with negligible reduction in seedling growth, while similar application of ancymidol or chlormequat did not reduce seedling growth.; Soaking verbena or marigold seeds in 10--500 mg·L -1 paclobutrazol solutions for 5--180 min did not reduce seed viability (tetrazolium test), but did reduce respiration and heat production rates in seeds. Reductions in seedling emergence and reduced respiration rates in paclobutrazol-treated seeds indicate that paclobutrazol imposed dormancy in verbena seeds. Washing restored rates of respiration and heat production in verbena and marigold seeds.; Seed coat morphology or hilum size in verbena, celosia, marigold, or cucumber could not be associated with seedling growth response to treating seeds with growth regulators. Scanning electron microscopy found deposits of Bonzi(TM) formulation on the surface of celosia seeds that were soaked in 500 mg·L-1 paclobutrazol solution for 180 min. Energy disperse x-ray spectroscopy detected increased aluminum concentration on the surface of seeds soaked in 500 (celosia and marigold) or 1000 (cucumber) mg·L-1 paclobutrazol solution for 180 min. (Abstract shortened by UMI.)...