Phalaenopsis orchid is a slow-growing crop that responds slowly to fertilization. In this study, we used 15N-labeled Johnson’s solution to investigate the accumulation and use of fertilizer nitrogen (N) during the vegetative and reproductive growth stages of Phalaenopsis Sogo Yukidian ‘V3’ with a focus on the nitrogen source for inflorescence development. Labeling of fertilizer applied to mature plants 6 weeks before forcing or at 6 weeks into forcing showed that in the inflorescence, the ratio of N derived from fertilizer applied 6 weeks before forcing to the N derived from fertilizer applied 6 weeks into forcing was 31% to 69%, which shows the importance of newly absorbed fertilizer for supplying the N needed for inflorescence development. The fate of fertilizer N applied during the small, medium, or large plant stage of vegetative Phalaenopsis Sogo Yukidian ‘V3’ was traced separately with 15N-labeling. The capacity of the plant to accumulate N after fertilizer application was different during the various stages of vegetative growth, with large plants having more N storage capacity as a result of their greater biomass. However, the percentage of the accumulated N that was later allocated to the inflorescence was similar regardless of the stage of fertilizer application: of the fertilizer N absorbed during various stages of the vegetative period, 6% to 8% was allocated to the inflorescence at the visible bud stage. This result highlights the mobility of N stored early on within the plant. By calculation, of the total N in the inflorescence at the visible bud stage, the N absorbed during the small, medium, and large plant stages contributed 7%, 11%, and 25%, respectively, whereas N applied after spiking made up the other 57%. This result indicates that both N stored during the vegetative stage and N applied during the reproductive stage contribute significantly to inflorescence development.
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.
Amplified fragment length polymorphism (AFLP) analyses were used to assess genetic diversity among 30 genotypes of watermelon [Citrullus lanatus (Thunb.) Mansf.] representing a broad genetic base, including breeding lines and commercial germplasm. Eight AFLP primer combinations selected from 64 primer combinations were polymophic. The polymorphism was 13.0% to 31.9% within the 28 cultivars examined, and 45.3% to 64.2% among all the genotypes. Each genotype could be successfully distinguished based on AFLP scoring. Cluster grouping of accessions based on the AFLP analysis was consistent with that from classification by pedigrees and ecotypes.