Petunia Hybrida Vilm Research Articles

The Incorporation of Herbicides into Organic Mulches for Weed Control in Ornamental Plantings1

Abstract N, N-dimethyl-2, 2-diphenylacetamide (diphenamid) and α, α, α,- trifluoro-2, 6-dinitro-N, N-dipropyl-p-toluidine (trifluralin) caused no injury to transplanted petunias (Petunia hybrida Vilm.) or marigolds (Tagetes patula L.) when incorporated in a mulch. Satisfactory broadleaf and grass weed control as denoted by indicator crops was achieved with both of these herbicides. Dichlobenil, 2,6-dichlorobenzonitrile, caused severe injury to both petunia and marigold transplants when applied in the herbicide-mulch combination. Control of broadleaf and grass indicator weeds with dichlobenil was excellent at all rates. Dimethyl tetrachloro terephthalate (DCPA) resulted in no visible injury to the marigold or petunia transplants when used in the herbicide-mulch combination, but control of grass and broadleaf indicator weeds was poor. When diphenamid and dichlobenil at the same rates were incorporated on peat moss, licorice root, pine bark or sugar cane mulches, no differences were observed among the mulches in regard to their ability to control weed growth. On established nursery stock, 2-chloro-4, 6-bis (ethylamino)-s-triazine (simazine) plus DCPA, simazine plus diphenamid, and 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (diuron), applied directly to the soil surface performed better than the herbicide-mulch combination at the lower rates. At higher rates, both the direct spray on the soil surface and the herbicide-mulch combination performed satisfactorily.

THE DEPENDENCE OF FLOWERING IN SEVERAL LONG‐DAY PLANTS ON THE SPECTRAL COMPOSITION OF LIGHT EXTENDING THE PHOTOPERIOD

The results of experiments in which the length, time, and spectral composition of photoperiod extensions and light breaks were varied are presented. The plants used included Hyoscyamus niger L. (annual henbane); Beta vulgaris L. (annual sugar beet); Hordeum vulgare L. (barley); Anethum graveolens L. (dill); Lolium temulentum L. (darnel); and Petunia hybrida Vilm. (petunia). Brief light breaks in the middle of each night failed to cause flower induction. Extended breaks and 8‐hr extensions of the photoperiod were effective, particularly those with light from BCJ, rubyred, or incandescent lamps. For all lamp types and species, 8‐hr extensions prior to each daylight period were more effective than those given at the end of each day. Four‐hour light breaks were most effective when given in the middle of each night. The flowering caused by 4‐hr breaks with BCJ light from 8 pm to 12 pm was suppressed when the BCJ light was preceded by 4 hr of fluorescent light. When light from BCJ or fluorescent lamps was interpolated for 2 hr at various times during 8‐hr extensions with light from the other type of lamp, BCJ light stimulated flowering the most, and fluorescent light inhibited it the most, when interpolated at the end of the daylight period. These results are discussed, and a model of how phytochrome participates in the flowering of long‐day plants is presented.

Further studies on the host range and properties of Trinidad cowpea mosaic virus

SUMMARYAdditional to previously recorded host reactions, Trinidad cowpea mosaic caused local lesions in French bean (Phaseolus vulgaris L.), Bengal bean (Mucuna aterrima, Holland), Petunia hybrida Vilm. and Chenopodium amaranticolor Coste & Reyn; the last two are the only known non‐leguminous hosts. C. amaranticolor and French bean were used to study some properties of the virus. Infectivity was not affected by exposure to pH values between 5 and 9.1, to a 50% saturated solution of ammonium sulphate or a 50% solution of acetone or ethyl alcohol. The virus has polyhedral particles with a mean diameter of 25 mμ (approx.).

Transmission of arabis mosaic virus by the nematode Xiphinema diversicaudatum (Micol.)

After dagger nematodes Xiphinema diversicaudatum (Micol.), were shown to transmit arabis mosaic virus to strawberry plants, the mode of transmission was studied using Petunia hybrida Vilm. seedlings as test plants. Approximately 30% of the nematodes reared on roots of infected strawberry plants transmitted the virus, and batches of ten nematodes caused infection in 90% of the test plants. Three days was the minimum test-feeding period in which transmission occurred, but longer periods resulted in a higher proportion of plants becoming infected. The vector retained the virus for long periods; some nematodes transmitted the virus to test plants in a second series without infecting those in the first on which presumably they fed for periods of 5, 10, and 20 days. Nematodes were still infective after fasting periods of up to 30 days in autoclaved sand. Noninfective nematodes acquired the virus in 24 hours, the minimum acquisition period tested, but a higher proportion were infective after 3 days on the source plants.

Effects of gibberellin on the growth and the flowering of several flower crops (The second report)

Following our previous work, successive experi-ments were performed to study the effects of gib-berellin on several flower crops, mainly on flower hastening, from the end of 1957 to the beginning of 1958. Gibberellin was applied to the plants as an aqueous solution and the concentrations of spray-ed solution were 25, 50 and 100 ppm. Potted plants in glasshouses were used for this experiment. 1. Gibberellin effects on flower hastening and flower-stalk elongation of cyclamen (Cyclamen Persicum MILL.) and that on vegetative growth stimu-lation of petunia (Petunia hybrida VILM.) were all apparent. These effects were already found in our previous experiment. As it seems that flowering of treated cyclamen was about 20_??_25 days earlier than control plant in this experiment, the effect of flower hastening on cyclamen was more remark-able than in the previous case, probably because of the applications of earlier spraying and more con-centrated solution. In petunia, its vegetative growth was not only stimulated, but flowering was also hastened. 2. Concerning the experiments with the mono-cotyledonous and bulbous plants, there were seen also flower hastening effects on freesia (Freesia refracta KLATT.), trumpet narcissus (Narcissus Pseudo-Narcissus L.) and Dutch iris(Iris hollandica HORT.), and the greatest extent of flower hastening on each plant was about 3 to 7 days. But there were hardly any effects on Easter lily (Lilium longi florum THUNB. var. giganteum HORT). As a matter of fact, flower hastening effect in the early spray-ing was more remarkable than that in the later spraying in case of freesia (Fujinomine) and Dutch iris. In regard to the plant height increase or flower-stem elongation of these plants, gibberellin had little or no effect. 3. Flowering of pansy (Viola tricolor L.) was hastened. Furthermore, plant height and peduncle length were markedly increased. 4. Flowering of Primula malacoides FRANCH. was also hastened. In addition to this effect, length of main Sower-stalk was remarkably increased and petiole length was also increased slightly, but these influences did not seem to cause an unfavour-able result to the market value of potted plants. 5. Young plant growth of calceolarria (Calceolarria rugosa RUIZ et PAV.) was stimulated by the application of gibberellin. Flowering of Amuradonis (Adonis amurensis REGEL et RADDE.) was hastened and vegetative growth was strikingly increased afterward. When the pruned branches of hydrangea (Hydrangea macrophylla SER.) were dipped into glass bottles containing gibberellin solution, bud, sprouting and leaf expansion were hastened by such gibberellin treatment. 6. There were no effects of injury or damage on the germination of pollen grains taken from treated plants of cyclamen and Primula malacoides FRANCH.

Effects of gibberellin on the growth and the flowering of several ornamental plants

This experiment was conducted for the purpose of studying the effects of gibberellin on growth and flowering of several ornamental plants. Gib-berellin was applied to the plants with spraying as aqueous solution and single or repeated applica-tions were made. Concentrations of sprayed solution were 20, 40 and 50ppm. Comparison was made between treat-ed plants and non-treated control plants. In many cases, potted plants were treated in glasshouse. 1. Flowering of cyclamen (Cyclamen persicum MILL.) was hastend and this influnce was more remarkable in 40ppm than in 20ppm. Further-more, flower size and length of flower stalk were significantly increased. 2. Flowering of freesia (Freesia refracta KLATT.) was also hastened, but this influence was likely to be limited only to the plants possessing flower buds of fairly advanced stage. No damage or injury caused by the application of gibberellin was found among pollen grains of treated flowers. 3. Plant height and shoot length of petunia (Petunia hybrida VILM.) were both remarkably in-creased. 4. The effect of flower hastening upon winter daphne (Daphne odora THUNB.) became manifest within a week after single application of gibbere-llin. 5. Flower size and length of flower stem of sweet pea (Lathyrus odoratus L.) were increased, but the effect of flower hastening was indistinct. 6. Concerning the experiments with Japanese cherry (Prunus yedoensis MATSUM.) and thunberg spires (Spiraea Thunbergii SIEB.) from which flower budded twigs were pruned and dipped into glass bottles containing water or gibberellin solution, bud sprouting was remarkably hastened and length of flower stem was strikingly increased, but flowering was never hastened by the appli-cation (spraying only or both spraying and dipping) of gibberellin. 7. There were hardly any effects on flowering of potted Kurume azalea (Rhododendron obtusum PLANCH.) in glasshouse, or of Japanese apricot (Prunus Mume SIEB. et ZUCC.), peach (Prunus Persica SIEB. et ZUCC.) and Japanese cherry (Prunus yedoensis MATSUM.) which were planted in the field.