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Passion fruit is a commercial crop of economic importance worldwide, with recent increases in demand for high-quality plants for commercial production. Plant tissue culture is widely used for the mass propagation of many commercial crops, however its application on passion fruit is challenged by the problem of low reproducibility, leaf chlorosis, and growth retardation resulted from in vitro culture. The aim of this study was to evaluate the effects of cytokinins and light quality on in vitro culture of nodal segments of passion fruit ‘Tainung No. 1’. Three aromatic cytokinins were tested in a modified MS basal medium. The bud proliferation rates of segments initiated on a media containing 1 mg·L−1 meta-topolin riboside (mTR) or benzyladenine (BA) were not significantly different at the same concentration. Buds cultured on medium supplemented with mTR grew and elongated for 4 weeks, while buds on a medium containing BA formed rosettes. After transfer to a medium without plant growth regulators (PGRs), shoots rooted spontaneously within 8 weeks. Furthermore, the effects of continuous propagation under a high proportion of red light affected the subsequent plant growth. Red LED induced an increase in the chlorophyll content (2.71 mg·g−1) compared with other light qualities (1.05–2.63 mg·g−1) and improved plantlet quality. Acclimated plants were grown in the field, and the flower morphology and fruit set were of commercial quality. Findings showed that replacing BA with mTR as the main cytokinin and using a high proportion of red light during the tissue culture induction period produced high-quality plantlets in 3 months. This system is economical and will be further developed for the commercial propagation of passion fruit vines in the future.
Phalaenopsis is currently the world’s number one potted flower crop. It is a slow-growing plant that responds slowly to nitrogen (N) fertilization and is noted for great resilience against N deficiency. Despite the great significance of N during the cultivation of Phalaenopsis, little has been studied on the uptake and partitioning of N in this crop. The stable isotope 15N was used as a tracer to investigate the uptake and partitioning of N and the roles of organs in sink and source relationship of N partitioning during different stages in Phalaenopsis. Fertilizer labeled with 15N was applied to Phalaenopsis Sogo Yukidian ‘V3’ during the vegetative growth stage on different parts of plants. Both leaves and roots were able to take up N. Nitrogen uptake efficiency of young roots was the highest, followed by old roots, whereas that of leaves was lowest. No difference of N uptake efficiency was found between the upper and lower leaf surfaces. Movement of fertilizer N to the leaves occurred as early as 0.5 day after fertilizer application to the roots. The partitioning of N depended on organ sink strength. During the vegetative growth stage, newly grown leaves and newly formed roots were major sinks. Sink strength of leaves decreased with the increase in leaf age. Stalks and flowers were major sinks during the reproductive growth stage. Mature leaves were a major location where N was stored and could serve as a N source during the reproductive growth stage and also for new leaf growth.
Paphiopedilum Clair de Lune ‘Edgard Van Belle’, an excellent Maudiae-type hybrid that has been propagated by artificial division for a long time. We studied its flower bud initiation, development of floral organs, and flowering habits with a view to providing information for flowering control and efficient commercial production. According to our research, the flower bud initiation phase of this cultivar begins in February every year, and 80% of the plants completed sepal primordium differentiation in March, The flower bud differentiation lasts for 6 to 7 months, until flowering in August. Within 1 to 3 months after flower bud differentiation, all tested plants differentiated lateral buds. After 5 to 6 months, the new, aboveground vegetative shoots reached their maximum growth, with an average plant height of 20 cm, five leaves, and a shoot dry weight of more than 3 g. From February to April of the following year, a new cycle of flower development and vegetative growth began. In addition, this cultivar was notably sensitivity to high ambient temperature during the late phase of flower development, with a flower bud drop rate as high as 33.3% under average day/night temperatures of 29.0/26.5 °C.