Effects of Plant Growth Regulators on the Growth and Flowering of Bougainvillea spp. and Passiflora spp.
Date Issued
2010
Date
2010
Author(s)
Liu, Fang-Yin
Abstract
Bougainvillea (Bougainvillea spp.) is an economically important ornamental flower in sub-tropical and tropical regions. Therefore, the ability to control the timing of flower production is of great importance commercially. After flowering, the flower bracts regularly abscise, and this process increases when bougainvilleas are subjected to indoor low-light conditions. Therefore, the aim of this research is to elucidate how plant growth regulators affect the growth and flowering of bougainvillea.
Most of the bougainvillea flowering shoots are inclining and vertical shoots are not flowering shoots, thus confirming the above observations in the natural environment. However, no direct or other studies have been performed to determine why inclined shoots have more flowers than vertical and horizontal shoots in the natural environment. In this work, therefore, bougainvillea shoots were artificially orientated vertically, horizontally and at an incline to study the effect of orientation on plant growth and the development of flower buds. Inclined shoots of bougainvillea have more flowering buds and more fully blooming flowers than either horizontal or vertical shoots. Inclined shoots had a higher endogenous ACC (1-aminocyclopropene-1-carboxylate) content and produced more ethylene than either horizontal or vertical shoots, indicating that more ACC in the inclined shoot is converted into ethylene, and the higher ethylene concentration in the inclined shoot causes it to mature earlier and flower sooner.
Additionally, this study examined bougainvillea shoots of different developmental stages, e.g., vegetative shoot, flowering shoot stage 1 with the thorn-inflorescence axis developed fully (FS1), flowering shoot stage 2 with visible flower bud (FS2), and flowering shoot stage 3 with blooming shoot (FS3) following their treatment with ethephon (2-chloroethylphosphonic acid). Experimental results indicated that ethephon treatment of the vegetative shoot of bougainvillea accelerates its shoot maturity and enhances flower formation. The same treatment also increases endogenous ethylene production of the vegetative shoot, subsequently facilitating flower formation in which the endogenous ACC content is lower than that of reproductive shoots (FS1, FS2, and FS3). Moreover, the ethephon treatment of reproductive bougainvillea shoots increases the ACC content beyond that of the vegetative shoot. Therefore, reproductive shoots produced more ethylene than vegetative shoots, subsequently inhibiting the development of flowers or even causing serious abscission of flower buds and leaf. This reveals that the role of ethylene in regulating the flowering control of bougainvillea is bi-directional. Results of this study demonstrate the significance of shoot maturity in the growth and flowering of the bougainvillea in which ethylene plays a major role.
Potted bougainvillea ‘Taipei Red’ in four different stages of bract development were sprayed with 100-800 nL L-1 1-MCP (1-methylcyclopropene) for 4 h and were moved to low-light indoor conditions after treatment. All of the 1-MCP treatments, especially the 800 nL L-1 treatment, inhibited ethylene production and thereby significantly prolonged the longevity of the bracts during the last bract stages (stages 3 and 4). Conversely, the 1-MCP treatments did not significantly prolong the longevity of bracts at early bract stages (stages 1 and 2). Additionally, treated with 1-MCP, NAA (1-naphthaleneacetic acid), SNA (sodium salt of naphthaleneacetic acid), IBA (indolebutyric acid), BA (6-benzylaminopurine), Put (diamine putrescine), SA (Salicylic acid), or STS (silver thiosulfate) and were moved to low-light indoor conditions after treatment. Experimental results indicated that 1-MCP, NAA, SNA, BA, Put, SA prolonged bract longevity. In addition, this treatment significantly reduced endogenous ACC content and ACC oxidase activity, suggesting that the inhibition of ethylene production was achieved via physiological metabolism. However, treatment with IBA or KH2PO4 (potassium dihydrogen phosphate) had no effect on the bract longevity at any stage. In the combined chemical treatments, NAA + STS or NAA + SA were effectively for prolonging bract longevity and contained less protein or chlorophyll degradation, decrease ACC oxidase or ethylene production than the control. In conclusion, we propose that combined chemical treatment was significantly prolonged bract longevity and more effectively than single chemical treatment at any stage.
Passion fruit (Passiflora spp.) is a tropical vine crop in the family Passifloraceae. In subtropical and tropical regions, such as the lowlands of Taiwan, passion fruit is grown outdoors, often flowering during the spring and early autumn. Both the growth and flowering of the Taiwan species of passion fruit are inhibited during the winter. The aim of this research was to elucidate the means by which plant growth regulators influence the growth and flowering of passion fruit.
Potted passion fruit ‘Tai-nung No.1’ was sprayed with either silver nitrate (AgNO3) or silver thiosulfate (STS), whereupon it was moved into low temperature conditions (20/15℃). The results showed that treatment with AgNO3 (0.5, 1 mM) or STS (0.5, 1 mM) induced flower formation and formed the first flower buds in all test plants within approximately 2 weeks post treatment. This was true for all tested plants with endogenous ACC content, ACC oxidase and ethylene lower than that of the controls at 20/15℃. The control plants exhibited no flower formation at 20/15℃. Additionally, flower buds were aborted in all treatment plants which were unable to flower successfully. The results showed that following the appearance of flower buds, subjecting the plants to cold stress prevented the full development of flowers, or a reduction in resistance to stress when the plants were still young.
We then treated plants with STS or AgNO3 to induce the formation of flowers under low temperature conditions (20/15 ℃), whereupon the plants were moved to higher temperatures of 25/20℃, in which the flower buds developed well. Reducing the node of first flower bud enabled the full flowering of the buds. Additionally, the maturity of passion fruit shoots also influenced resistance to reduced temperatures. We divided the passion fruit into three stages according to the number of nodes (P1- 5-11 nodes, P2- 12-18 nodes, P3-19-25 nodes) after spraying with 1 mM STS, under low temperature conditions. The results showed that the flower buds of young plant (P1) were all aborted following injury due to chilling. Older plants (P2, P3), with more mature shoots, continued the development of flowers.
Salicylic acid (SA) inhibits the production of ethylene, thereby enhancing resistance to biotic and abiotic stress in the growth and development of plants. Variations in the pH values of SA has a significantly effect the growth of passion fruit. An SA solution of pH 6.5 promoted growth and the formation of passion fruit flowers under low temperature conditions. In contrast, treatment with an SA solution of pH 2.4 resulted in slow growth, and no formation of flower buds. The concentration of SA also influences young plants (P1, 5-11 nodes), which were prompted to form flowers by higher concentrations of SA (>2.5 mM). Old plants (P2, 12-18 nodes) with mature shoots responded only to low concentrations of SA (0.5-2.0 mM) to achieve the formation of flowers. The treatment of passion fruit with SA could help to develop flowering under low temperature conditions; however, flower buds still have a high abortion rate. On the other hand, treatment with SA to induce flower formation under low temperature conditions (20/15 ℃), followed by a shift to higher temperatures (25/20℃) leads to the development of full flowers, with a reduction in the abortion rate of flower buds.
Subjects
Bougainvillea
Passionfruit
Ethylene
Flowering
Type
thesis
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