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A necrotic disorder occurs on upper leaves of many oriental hybrid lily (Lilium L.) cultivars, including the most-widely-grown `Star Gazer'. We term this disorder “upper leaf necrosis” (ULN) and hypothesize that it is a calcium (Ca) deficiency. We demonstrated that Ca concentration in necrosed tissues was nearly six-fold below that of normal leaves (0.10% vs. 0.57% dry weight), and that Ca concentration was negatively associated with percentage necrosed leaf area. It was concluded that ULN is a Ca deficiency disorder. When the symptoms were slight, early ULN symptoms appeared as tiny depressed spots on the lower surface of the leaf, or as water-soaked areas when the disorder was severe. Most commonly, ULN began on the leaf margin. The injured areas turned brown, leading to leaf curling, distortion, or tip death. ULN occurred on leaves associated with flower buds and leaves immediately below the flower buds. For the plants grown from 16-18 cm circumference bulbs, the five leaves directly below the flower buds and larger leaves associated with the 1st and the 2nd flower buds were most susceptible. In general, flower buds were not affected by ULN, and continued to develop and flower normally, even though they were associated with subtending, highly distorted leaves. Eighty-five percent of plants began to exhibit ULN symptoms 30-40 days after planting (i.e., 24-34 days after shoot emergence). This was the stage when the 6th or 7th leaf under the bottom flower bud was just unfolded. Light was not the main factor that initiated ULN, however, ULN severity was greatly increased by light reduction, as leaf transpiration was reduced.

Upper leaf necrosis (ULN) on Lilium `Star Gazer' has been recently demonstrated to be a calcium (Ca) deficiency disorder. In the current studies, we confirmed this by using a Ca-free nutrient regime to reproduce ULN symptoms. The ability of a bulbous storage organ to supply calcium to a growing shoot is poorly understood. Therefore, we conducted experiments to determine Ca partitioning during early growth stages, and under suboptimal Ca levels to determine how the bulb affects the symptomatology. The results indicated that ULN is originally caused by an insufficient Ca supply from the bulb. In the most susceptible period, bulb dry matter decreased dramatically and Ca concentrations in immature folded leaves dropped to very low levels. Consequently, necrosis began to appear on the upper, young leaves. The bulb was able to supply Ca to other organs, but only to a limited extent since Ca concentration in bulbs was low (0.04% w/w). To confirm this result, we cultivated lilies with low-Ca or Ca-free nutrient solution and obtained bulbs with extremely low internal Ca concentrations. Upon forcing these low-Ca bulbs, we found, as expected, prominent necrosis symptoms on the lower and middle leaves. Data suggested the lower and middle leaves relied more on Ca supplied from the bulb, while upper leaves and flowers relied more on Ca uptake from the roots. Different organs have different Ca requirements, and tissue sensitivity to Ca deficiency varies according to the growth stage.

Upper leaf necrosis (ULN) on Lilium `Star Gazer' has been shown to be a calcium (Ca) deficiency disorder. Initial symptoms of ULN tend to appear on leaf margins. Before flower buds are visible, young expanding leaves are congested and overlap each other on the margin. In the current study, we examined the relationship between leaf enclosure, transpiration, and upper leaf necrosis. We demonstrated that low transpiration rate and enclosure of young leaves played an important role in the occurrence of ULN. Young expanding leaves are low transpiration organs. The younger the leaf, the lower the transpiration rate and Ca concentration. Leaf enclosure further reduced transpiration of these young leaves and promoted ULN. Upper leaf necrosis was suppressed by manually unfolding the leaves using a technique we refer to as artificial leaf unfolding (ALU). ALU minimized leaf congestion, exposing leaves that were previously enclosed. We demonstrated that the effect of ALU was not the consequence of thigmomorphogenesis, as ULN was not reduced by mechanical perturbation in lieu of ALU. With ALU, transpiration of upper leaves was significantly increased and Ca concentration of the first leaf immediately below the flower buds was increased from 0.05% to 0.20%. We concluded that leaf enclosure promoted ULN occurrence, and ALU suppressed ULN primarily by increasing transpiration. The use of overhead fans to increase airflow over the tops of the plants significantly reduced both ULN incidence and severity.

Plants of Phalaenopsis orchid are known for their great resilience and ability to flower under less than ideal conditions, including long periods without fertilization. Significant nutrient storage is thought to account for this characteristic; however, the use of stored nutrients in Phalaenopsis has not been fully studied. We used ¹⁵N-labeled Johnson’s solution to trace the use of stored nitrogen (N) and recently absorbed fertilizer N in Phalaenopsis given various fertilizer levels during forcing. By separately labeling fertilizer N applied to Phalaenopsis Sogo Yukidian ‘V3’ plants 6 weeks before and 6 weeks into forcing, we found in the inflorescence that the ratio of N derived from fertilizer applied 6 weeks before forcing to the N derived from fertilizer applied 6 weeks into forcing was 43% to 57%. With 90% reduction in fertilizer concentration during the reproductive stage, the ratio increased to 89% to 11%, indicating that stored N becomes a significant N source for inflorescence development when fertility becomes limited. Reducing fertilizer level during the reproductive stage from full-strength Johnson’s solution down to zero decreased the dry weight of newly grown leaves, reduced the number of flowers from 10.8 to 8.9, and slightly increased the time required between initiation of forcing and anthesis. However, the overall effect of reduced fertilization on the growth and flowering of Phalaenopsis Sogo Yukidian ‘V3’ plants in this study was slight, because under little or no fertilization, more stored N was mobilized and this was sufficient to meet most of the N demand for inflorescence development.

Phalaenopsis is one of the most important ornamental crops and is frequently transported between continents. In this study, the effects of the duration and temperature of simulated dark shipping (SDS) and the temperature difference between cultivation greenhouses and shipping containers on the carbohydrate status and post-shipping performance were investigated. With a prolonged SDS from 0 to 40 days at 20 °C, the percentage of the vegetative Phalaenopsis Sogo Yukidian ‘V3’ plants with yellowed leaves increased from 0% to 50%, and the total carbohydrate contents in the shoot and roots gradually decreased over time. Furthermore, roots had greater reductions in glucose and fructose concentrations than the shoot after 40 days of SDS. After 7 days of SDS, the youngest bud and the nearly open bud on blooming plants of Phalaenopsis amabilis were found to be the most negatively affected among flowers and buds of all stages. These buds had lower soluble sugar concentrations and flower longevities compared with those of unshipped plants. The results of a temperature experiment showed that yellowing of the leaves and chilling injury (CI) occurred in Phalaenopsis Sogo Yukidian ‘V3’ after 21 days of SDS at 25 and 15 °C, respectively, regardless of pre-shipping temperature acclimation. However, 10 days of acclimation at 25/20 °C (day/night) before SDS reduced CI and reduced the time to inflorescence emergence. Higher accumulations of sucrose in the shoot and glucose and fructose in roots were found after 21 days of SDS at 15 °C compared with those at 25 and 20 °C. In conclusion, the carbohydrate status of Phalaenopsis was positively related to the post-performance quality. A reduction in the commercial quality after SDS may be attributed to a decline in carbohydrates. The optimal temperature for long-term dark shipping is 20 °C, and we recommend providing 10 days of lower-temperature acclimation (25/20 °C) before shipping to enhance the chilling tolerance and to promote early spiking of Phalaenopsis plants.

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.