Effects of Nitrogen and the Various Forms of Nitrogen on Phalaenopsis Orchid—A Review

Abstract

<jats:p>Growers realize the importance of nitrogen (N) on the vegetative growth of phalaenopsis orchids (hybrids of <jats:italic>Phalaenopsis</jats:italic> sp.), but often overlook its influence on reproductive growth. Low N may result in slow plant growth, pale-green leaves, abscission of lower leaves, and few flowers in phalaenopsis. Increasing N concentration up to 200 mg·L<jats:sup>−1</jats:sup> promotes leaf growth and increases flower count. High N concentration promotes lateral branching on the flowering stalk, thereby greatly increasing the total flower count and elevating the commercial value. It is important that N be continually applied during the forcing period for best flowering performance, particularly for those that had undergone international shipping. For the vegetative phalaenopsis plants that are induced to flower without being shipped internationally, the N that is already in the plant before spiking provides 43% and the N being absorbed by roots after cooling provides 57% of the total N in the inflorescence at time of visible bud. When insufficiently fertilized or no fertilization is applied during the forcing period, more of the existing N in a plant is mobilized for inflorescence development. Phalaenopsis roots can take up all three forms of N [i.e., nitrate (NO<jats:sub>3</jats:sub>-N), ammonium (NH<jats:sub>4</jats:sub>-N), and urea] directly. In two studies, phalaenopsis plants were supplied with the same amount of total N but with varying NO<jats:sub>3</jats:sub>-N from 100%, 75%, 50%, 25%, to 0% (a common N concentration was achieved by the substitution of the respective balance with NH<jats:sub>4</jats:sub>-N). Plants were smaller when receiving 75% or 100% NH<jats:sub>4</jats:sub>-N with a tendency of decreasing top leaf width and whole-plant leaf spread as NO<jats:sub>3</jats:sub>-N decreased from 100% to 0%. Spiking was delayed and spiking rate decreased when plants were grown in sphagnum moss, but not a bark mix, and received more than 50% of the N in NH<jats:sub>4</jats:sub>-N. As the ratio between NO<jats:sub>3</jats:sub>-N and NH<jats:sub>4</jats:sub>-N increased, flowers became increasingly larger. The negative effects of low ratios of NO<jats:sub>3</jats:sub>-N to NH<jats:sub>4</jats:sub>-N were more severe in the second flowering cycle. When supplied with 50% or more NH<jats:sub>4</jats:sub>-N, the absorption of cations by phalaenopsis roots declined, with reduced concentrations of calcium and magnesium in plants, while symptoms of ammonium toxicity appeared, including growth retardation, chlorotic leaves, and necrotic roots. In conclusion, adequate N and its continual supply during both vegetative and reproductive stages are recommended for the best growth and flowering of phalaenopsis. Since phalaenopsis plants prefer N in the NO<jats:sub>3</jats:sub>-N form, it is suggested that growers choose and apply a fertilizer with nitrate as the major N source.</jats:p>

Physiological diversity of orchids

“…Although the effects of nitrogen on orchid growth under cultivation conditions have been confirmed by some studies, the demand for that nutrient is relatively low (Mou et al., 2012, Wang and Chang, 2017). Within a certain range, increasing the nitrogen concentration can promote vegetative growth, and increase the number of flowers produced by genera such as Phalaenopsis , Cattleya , and Dendrobium .…”

“…Spiking is delayed and the spiking rate is reduced when those plants receive more than 50% NH4+. As the ratio between NO3− and NH4− rises, flowers become increasingly larger (Wang and Chang, 2017). Flower buds and flowers of C. sinense form normally when plants are treated with NO3− at 1 or 10 mmol L −1 , but no flower buds form regardless of the level of NH4+ treatment (Pan and Chen, 1994).…”

“…Within a certain range, increasing the nitrogen concentration can promote vegetative growth, and increase the number of flowers produced by genera such as Phalaenopsis , Cattleya , and Dendrobium . However, flowering is delayed when the nitrogen concentration is too high (Bichsel et al., 2008, Wang and Chang, 2017). The demand for nitrogen by plants of P. armeniacum is higher at the vegetative growth stage but lower at the reproductive stage.…”

Silicon foliar application on nutrition and growth of Phalaenopsis and Dendrobium orchids

“…There are several studies on orchid nutrition and fertilization in the literature (Naik et al, 2009;Wang and Chang, 2017) because orchid farming represents one of the most economically important activities of the global nursery industry (Teixeira da Silva, 2013). However, to our knowledge, there are no reports on the application of Si during the entire vegetative cycle.…”

Fertilization methods and substrate particle size differentially affect growth and macronutrient status of Laelia anceps subsp. anceps

“…However, the mechanisms of nutrient uptake in wild epiphytic orchids are not entirely known, while the effects of the form and concentration of N on growth and flowering of orchids are poorly understood (Zhang et al, 2018). For Phalaenopsis, the most studied genus of orchids, an adequate supply of N is recommended, both in vegetative and reproductive stages to achieve the best growth and flowering (Wang and Chang, 2017).…”