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The effects of several shading materials on the response of Gardenia jasminoides Ellis to paclobutrazol were investigated under greenhouse conditions. The three main plot treatments were shading (0%, 67%, 98%), and paclobutrazol (0.0, 0.5, 1.0, and 2 mg/pot) was applied as a soil drench in each main plot after pinching the plants. Both plant size and the number of flower buds per plant decreased as the rate of paclobutrazol increased at all levels of shading. The efficacy of paclobutrazol, however, was generally less under heavy shade, as both translocation of the growth retardant and photosynthesis were reduced. Moderate shading (67%) did not affect the size of plants receiving 0.0 or 0.5 mg of paclobutrazol per pot, but plants grown under heavy shade (98%) were 74% as large as similarly treated nonshaded plants. Medium shade reduced the size of plants receiving 1 and 2 mg paclobutrazol 4% and 6%, respectively, relative to that of similarly treated nonshaded plants, whereas heavy shade reduced plant size 11%. The number of flower buds per plant was reduced 30% by moderate shading, 90% by heavy shading. Significant quadratic relationships were observed between the rate of paclobutrazol applied and (1) plant size, and (2) the number of flower buds per plant. Chemical name used: ±-(R*,R*)-β–[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)-1H-(1,2,4-triazol)-1-ethanol (paclobutrazol).

Kamoutsis, A., Chronopoulou-Sereli, A. and Holevas, C. 1998. Interaction of triapenthenol and environmental factors on the growth and flower bud formation of Gardenia jasminoides Ellis. Can. J. Plant Sci. 78: 635-640. The interaction effects between total solar radiation, air temperature and relative humidity with different concentrations of the plant growth regulator triapenthenol (Baronet) on the vegetative growth and the formation of flower buds of potted gardenia (Gardenia jasminoides Ellis) plants were studied in glasshouse experiments.Triapenthenol was applied as a soil drench at concentrations of 0, 70, 140 and 280 mg L -1 to plants under each of three radiation levels of about 250 (P1), 90 (P2) and 25 (P3) Wm -2 . It was established that the maximum temperature was the most critical environmental factor to plant development at all radiation levels. Lengths of new lateral shoots after pinching and the number of flower buds/plant were significantly reduced when radiation was reduced and triapenthenol concentrations increased. The interaction between total radiation and triapenthenol concentration significantly affected the number of flower buds/plant. An increase in triapenthenol concentration and a reduction of total radiation caused increased wrinkling of the leaves.In the unshaded plot (P1), the 140 mg L -1 triapenthenol concentration produced high-quality plants that were shorter than the untreated ones with more flower buds/plant during the growth period. In the moderately shaded plot (P2), the best market-quality plants were those treated with 70 mg L -1 triapenthenol.Key words: Gardenia jasminoides, temperature, total solar radiation, triapenthenol, relative humidity Kamoutsis, A., Chronopoulou-Sereli, A. et Holevas, C. 1998. Interaction de triapenthenol et des facteurs environmentales sur la croissance et la formation des boutons florales de Gardenia jasminoides Ellis. Can. J. Plant Sci. 78: 635-640. Les effets de l'interaction entre la radiation solaire totale, la température ambiente et l'humidité relative et les concentrations différentes du régulateur de la croissance du triapenthenol (Baronet) sur la croissance végétative et la formation des boutons florales des plantes de gardenia (Gardenia jasminoides Ellis) mises en pots a été étudiée au cours des experiences en serre.Le triapenthenol a été appliqué en arrosage du sol aux concentrations de 0, 70, 140, et 280 mg L -1 aux plantes sous trois niveaux d'intensité de radiation totale d'environ 250 (P1), 90 (P2) et 25 (P3) Wm -2 respectivement. Il était établi que la temperature maximale etait le facteur environmental le plus important pour le développement des plantes sous tous les trois niveaux de radiation. Les longueurs de nouveaux pousses laterales après le pincage et le nombre de boutons florales/plante été réduits significativement quand la radiation est réduite et les concentrations du triapenthenol sont augmentées. L'interaction entre le niveau de la radiation et la concentration du triapenthenol ont affecté significativement le nombre d...