Open access peer-reviewed chapter

Nitrogen in Flowers

By Soraya Ruamrungsri, Kanokwan Panjama, Takuji Ohyama and Chaiartid Inkham

Submitted: September 14th 2020Reviewed: May 6th 2021Published: May 29th 2021

DOI: 10.5772/intechopen.98273

Downloaded: 83

Abstract

This chapter explores the literature and research on nitrogen in flowers. An overview of nitrogen deficiency symptoms in some flowers, i.e., Curcuma alismatifolia (ornamental curcuma), Tagetes erecta (marigold), Zinnia violacea (zinnia), and Gomphrena globose (gomphrena) were presented. Additionally, nitrogen uptake, translocation, and application in some flowers, i.e., ornamental curcuma, narcissus, orchids, and rose, were discussed in this chapter. Nitrogen affects the life cycle of flower, including vegetative and reproductive phases. Flower size, stem length, number of flowers per plant, and color were reduced by nitrogen deficiency. Therefore, the optimum level of nitrogen supply in each growth stage is important for flower crop production.

Keywords

  • nitrogen deficiency
  • nitrogen uptake
  • nitrogen application
  • nitrogen translocation
  • flowers

1. Introduction

Flower crops, similar to other horticultural crops, require optimum fertilizer for a good quality flower size, stem length, number of florets, stem, and petal color. Essential elements, especially nitrogen, play an important role in growth and development in each stage of the life cycle. Different genera have different nitrogen requirements. Generally, they have a nitrogen content that is enough for root emergence and shoot sprouting. However, flowers grown from seeds may require fertilizer as soon as root emergence. A lack of fertilizer supply will lead to severe nutrient deficiency. Seed germination starts with water uptake, and then food reserves, i.e., carbohydrates and storage proteins, are oxidized for the growth process [1]. Flower seedlings show deficiency symptoms when the fertilizer supply is not enough. Nitrogen is an especially important element in the life cycle of plants from seedlings to the vegetative stage and flowering until senescence. It affects flower qualities, such as size, stem length, and color. This chapter focuses on the role of nitrogen in some economic flower crops. Most information was derived from our research experiments and some are unpublished data.

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2. Nitrogen deficiency symptoms in different flower species

2.1 Curcuma alismatifolia(ornamental curcuma)

Nitrogen deficiency (-N) affected the growth and characteristics of C. alismatifolia(Table 1 and Figure 1). Most growth parameters, such as plant height, root length, leaf area, and total fresh and dry weight, were higher when plants were supplied with a complete nutrient solution, rather than -N treatment (Table 1). However, there was no significant difference in the number of leaves per plant between plants supplied with complete nutrient solution and -N treatment (Table 1). The characterization of nitrogen deficiency symptoms in C. alismatifloliawere evaluated at the flowering stage (12 weeks after planting). Leaves are the main plant part in which visual symptoms of the plant’s response to nitrogen deficiency are usually observed. When there is a nitrogen deficit, older leaves of C. alismatifoliaturn yellow and brown, while young leaves still appear green (Figure 1). The old leaves’ green color intensity in -N treatment was lower than those treated with the complete nutrient solution (34.2 and 57.1 SPAD unit, respectively). There was no significant difference among treatments in young leaves (Table 1). This result could explain nutrient remobilization processes in plants. Nitrogen is a macronutrient that is highly mobile in the phloem [2]; therefore, in N deficit conditions, nitrogen in old leaves of C. alismatifoliamay be remobilized and translocate to young leaves. The remobilization of nutrients is frequently associated with foliar senescence, which makes nutrients available for younger plant organs and contributes to nutrient use efficiency [3].

Nutrient solutionPlant growth at flowering stage (12 weeks after planting)
Plant Height (cm)No. leaves per plantRoot length (cm)Leaf green color intensity (SPAD unit)Leaf area (cm2)Total fresh weight (g)Total dry weight (g)
Old leafYoung Leaf
Complete49.1 a5.0 a42.8 a57.1 a52.5 a253.8 a285.0 a31.3 a
-N36.0 b4.3 a40.6 b34.2 b52.8 a191.2 b111.4 b14.7 b
%CV8.78.80.910.84.910.611.012.4
LSD 0.05*NS**NS***

Table 1.

Plant growth of Curcuma alismatifoliatreated with complete nutrient solution or nitrogen deficiency (-N) at the flowering stage (12 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05). NS = not significant.


Figure 1.

Growth and flower quality ofCurcuma alismatifoliawas affected by complete nutrient solution (control) and nitrogen deficiency (-N) treatment at the flowering stage (12 weeks after planting). (photo by Chaiartid Inkham).

Nitrogen deficiency delays flowering in C. alismatifoliaand decreased flower quality in term of inflorescent length. However, there were no significant differences in inflorescence width, stalk length, and number of inflorescences per plant (Table 2 and Figure 1). Nitrogen deficiency delayed flowering in narrow-leafed lupin [4]. The production of C. alismatifolia,in terms of flower quality and rhizome yield, depends on the response to N fertilizers [5]. Nitrogen-deficient plants are stunted and the quality of their flowers and rhizomes is significantly decreased. The increase of nitrogen from 0 to 50 mg L−1 increased the number of flowering shoots and, consequently, the number of rhizomes [6].

Nutrient solutionFlower quality
Days to flowering (day)Inflorescence width (cm)Inflorescence length (cm)Stalk length (cm)No. inflorescence per plant
Complete70.7 b6.9 a11.8 a34.3 a1.0 a
-N78.3 a5.8 a9.9 b29.4 a1.0 a
%CV0.89.74.78.10
LSD 0.05*NS*NSNS

Table 2.

Flower quality of Curcuma alismatifoliatreated with complete nutrient solution or nitrogen deficiency (-N) at the flowering stage (12 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05). NS = not significant.


2.2 Tagetes erectaL. (Marigold)

The overall growth parameters of marigold were decreased under nitrogen deficit conditions (Table 1 and Figure 2). At 8 weeks after planting, plants in the -N treatment were stunted with a plant height of only 47.5 cm, which was 42.2 cm shorter than plants in the complete nutrient solution treatment. Moreover, there was a dramatic decrease in leaf area and the total fresh weight of marigolds grown under -N treatment when compared with complete nutrient solution treatment (decreasing 82 and 90%, respectively) (Table 3). Leaf green color intensity of marigold was detected both in young leaves and old leaves to evaluate visual symptoms of plants grown under -N conditions. The results showed that leaf green color intensity of marigold in both young and older leaves was lower when grown under -N treatment than grown under complete nutrient solution treatment (Table 3). In addition, the leaves of plants under -N treatment were smaller than those under complete nutrient solution treatment. Older leaves turned yellow, red and brown, while young leaves had symptoms of chlorosis and turned light yellow (Figure 2). Plant height, plant spread, and the number of primary branches per plant of African marigold increased significantly with the increase in nitrogen level from 0 to 30 g m−2 [7]. A suitable supply of N enhanced plant growth efficiency, thus increasing plant yield and flower quality [8].

Figure 2.

Growth and flower quality of marigold was affected by complete nutrient solution (control) and nitrogen deficiency (-N) treatments at the flowering stage (8 weeks after planting). (photo by Chaiartid Inkham).

Nutrient solutionPlant growth at flowering stage (8 weeks after planting)
Plant Height (cm)Root length (cm)Leaf green color intensity (SPAD unit)Leaf area (cm2)Total fresh weight (g)
Old leafYoung Leaf
Complete89.7 a28.3 b43.9 a45.5 a3,990.3 a889.8 a
-N47.5 b36.5 a23.2 b22.2 b706.3 b88.7 b
%CV8.95.914.119.040.32.7
LSD 0.05******

Table 3.

Plant growth of marigold treated with complete nutrient solution or nitrogen deficiency (-N) at the flowering stage (8 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05).


Flowering of marigold was delayed under nitrogen deficiency condition (about 12 days delay when compared with complete nutrient treatment) (Table 4). Furthermore, the flower quality in terms of flower width, flower length, and stalk length were also reduced in plants in the -N treatment compared to those treated with the complete nutrient solution (Table 4, Figure 2). The flower yield of marigold was highly sensitive to nitrogen deficiency, since there was a 90% decrease in the number of flowers per plant when the plants were grown under -N treatment compared with the complete nutrient solution treatment (Table 4). In marigold (Calendula officinalisL. ‘TOKAJ’), nitrogen fertilization had a significant impact on the number of flower heads per plant (especially on the second-rank branches) [9].

Nutrient solutionFlower quality
Days to flowering (day)Flower width (cm)Flower length (cm)Stalk length (cm)No. flowers per plant
Complete55.7 b8.5 a4.8 a12.7 a10.0 a
-N67.7 a4.8 b2.0 b4.5 b1.0 b
%CV0.918.715.827.325.7
LSD 0.05*****

Table 4.

Flower quality of marigold treated with complete nutrient solution or nitrogen deficiency (-N) treatment at the flowering stage (8 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05).


2.3 Zinnia violacea Cav.(zinnia)

Nitrogen deficiency caused a decrease in plant height, number of leaves per plant, and root length of zinnia at 9 weeks after planting (Table 5). Additionally, yields of zinnia in terms of leaves area, total fresh weight, and total dry weight also decreased when grown plant under -N condition compared with those treated with complete nutrient solution; the percentage of reduction was 85, 81, and 84%, respectively (Table 5). Visual symptoms of nitrogen deficiency in zinnia were observed at the flowering stage. In -N treatment, plants were stunted with less branches (Figure 3). Old leaves in the -N treatment turned yellow, while young leaves remained green in both treatments (Figure 3). Visual symptoms observed on leaves had a similar trend with leaf green color intensity detected by a chlorophyll meter (SPAD) (Table 5). The results indicated that there was a significantly different leaf green color intensity in old leaves between plants treated with -N and complete nutrient solution. There was not a significant difference in young leaves (Table 5). Growth of Zinnia elegansCv. Meteor increased with increasing nitrogen concentration from 0 to 20 g N/pot, i.e., plant growth rate (42% increase), plant height (28% increase), number of lateral shoots (56% increase), length of lateral shoots (17% increase), number of leaves (59% increase), and leaf area (40% increase) [10].

Nutrient solutionPlant growth at flowering stage (9 weeks after planting)
Plant Height (cm)No. leaves per plantRoots length (cm)Leaf green color intensity (SPAD unit)Leaf area (cm2)Total fresh weight (g)Total dry weight (g)
Old leafYoung Leaf
Complete25.0 a284.7 a50.3 a32.8 a30.5 a7,950.0 a84.4 a11.7 a
-N17.3 b44.0 b24.0 b16.7 b27.2 a1,155.8 b15.7 b1.9 b
%CV10.717.415.714.39.49.69.919.4
LSD 0.05****NS***

Table 5.

Plant growth of zinnia treated with complete nutrient solution or nitrogen deficiency (-N) at the flowering stage (9 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05). NS = not significant.


Figure 3.

Growth and flower quality of zinnia was affected by complete nutrient solution (control) and nitrogen deficiency (-N) treatment at the flowering stage (9 weeks after planting). (photo by Chaiartid Inkham).

The flowering of zinnia was delayed for 15 days when plants were grown under -N treatment (Table 6). Nitrogen deficiency decreased flower quality in term of flower width (50% decrease), number of flower buds per plant (80% decrease), and number of flowers per plant (74% decrease) in zinnia (Table 6). Visual symptoms of zinnia flowers response to -N treatment were smaller flowers and a reduced number of petals compared to those treated with complete nutrient solution (Table 6 and Figure 3). In Zinnia eleganscv. Meteor, flower quality increased when supplied with 10 g N/pot compared with 0 g N/pot (18% increase in number of flowers per plant, 52.5% increase in flower size, and blooming stage was prolonged for 11 days) [10]. A high dose of nitrogen (20 g N/pot) negatively impacted flowering when compared with those supplied 10 g N/pot, i.e., delay emergence of first flower for 8 days, 20% decrease in the number of flowers per plant, and 17.5% decrease in flower size [10].

Nutrient solutionFlower quality
Days to flowering (day)Flowers width (cm)No. flower buds per plantNo. flowers per plant
Complete54.3 b6.2 a54.0 a26.3 a
-N69.3 a3.1 b10.7 b6.7 b
%CV3.49.811.618.5
LSD 0.05****

Table 6.

Flower quality of zinnia treated with complete nutrient solution or nitrogen deficiency (-N) at the flowering stage (9 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05).


2.4 Gomphrena globose(gomphrena)

The growth of gomphrena was affected by nitrogen deficiency (Table 7). In the -N treatment, plants were stunted, with plant height 34.4 cm lower than those in the complete nutrient treatment (49.3 cm). Shorter root length was also observed in plants under -N treatment. Leaf area, total fresh weight, and total dry weight were dramatically decreased when plants were grown under nitrogen deficiency conditions with 80, 85, and 85% reductions, respectively (Table 7). Visual symptoms of nitrogen deficiency were a changed leaf color. Both old and young leaves in the -N treatment turned yellow with SPAD values lower than those under complete nutrient treatment (Table 7 and Figure 4). Moreover, a decrease in the number of new branches was observed when the plant was grown under -N treatment (Figure 4).

Nutrient solutionPlant growth at flowering stage (13 weeks after planting)
Plant Height (cm)No. leaves per plantRoot length (cm)Leaf green color intensity (SPAD unit)Leaf area (cm2)Total fresh weight (g)Total dry weight (g)
Old leafYoung Leaf
Complete49.3 a49.3 a59.7 a30.6 a37.7 a1,251.8 a250.6 a39.2 a
-N34.4 b21.7 b32.6 b22.1 b26.6 b254.2 b38.0 b6.0 b
%CV13.218.010.09.6717.817.918.018.0
LSD 0.05********

Table 7.

Plant growth of gomphrena treated with complete nutrient solution or nitrogen deficiency (-N) at the flowering stage (13 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05).


Figure 4.

Growth and flower quality of Gomphrena was affected by complete nutrient solution (control) and nitrogen deficiency (-N) treatment at the flowering stage (13 weeks after planting). (photo by Chaiartid Inkham).

The flower quality of gomphrena was low under nitrogen deficiency conditions (Table 8). The flowering of gomphrena was delayed for 8 days when the plant lacked nitrogen. Additionally, flower size in terms of flower width, flower length, and stalk length were reduced under nitrogen deficit treatment. The number of flowers per plant also decreased by about 57% in the -N treatment compared with the complete nutrient treatment (Table 8 and Figure 4).

Nutrient solutionFlower quality
Days to flowering (day)Flower width (cm)Flower length (cm)Stalk length (cm)No. flowers per plant
complete86.7 a2.1 a2.6 a14.1 a8.7 a
-N94.3 b1.6 b1.5 b9.6 b3.7 b
%CV0.66.916.18.129.6
LSD 0.05*****

Table 8.

Flower quality of gomphrena treated with complete nutrient solution or nitrogen deficiency (-N) treatment at the flowering stage (13 weeks after planting).

Means within the same column followed by different letters were significantly different in an LSD test; (p ≤ 0.05).


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3. Uptake, translocation, and nitrogen application in different flower species

Plants take up inorganic nitrogen, mostly in the form of ammonium (NH4+) and/or nitrate (NO3). Uptake depends on the plant species and growth stage [11]. The translocation of N, including the free amino acid form, from roots to leaves could be done via the xylem. Some flowers can also utilize N via N2-fixation by endophytic bacteria, such as Curcuma alismatifoliaand Vanda. Some studies have shown the uptake, translocation, and assimilation of N-forms in flowers at different growth stages using 15N-tracer feeding.

3.1 Curcuma alismatifolia

Curcuma alismatifolia, commonly known as the Siam tulip, is a flower bulb in the family Zingiberaceae. It is an economical flower crop in Thailand. Growers export rhizomes and cut flowers to other countries, including Japan, the Netherlands, the USA. The inflorescence of this plant is showy with pink and greenish bracts on a long peduncle (Figure 5A). The storage organ is the underground part of the plant and is so-called rhizome modified from the stem and attached to some storage roots (Figure 5B).

Figure 5.

Inflorescence (A) and rhizome (B) ofCurcuma alismatifoliaGagnep. (photo by Chaiartid Inkham).

The rhizome is a major organ to store N, while carbohydrates are mostly stored in storage roots. The N concentration in the stubbed rhizome is 41–45 mgN gDW−1, on average, while it was about 9–14 mgN gDW−1 in storage roots. Most of N in dormant rhizome was in PBS-insoluble form (79%), as a storage protein localized in the cytosol and cell wall, which presented as 10.6 and 12.0 kDa bands by SDS-PAGE staining. They contained five peptides and one peptide, respectively, when separated by 2D-PAGE. N in the storage roots was assimilated into different forms of free amino acids and protein compounds. The total free amino acid concentration in storage roots was higher than in the rhizome (343.8 and 109.0 μmol gDW−1, respectively) when the plants were supplied with 50 mgN L−1. Most of the free amino acids in the rhizome and storage roots were arginine and glutamic acid, respectively. Proteins in the rhizome were at a higher concentration than those in storage roots with 197.4 and 46.7 mgN gDW−1, respectively. A lack of N reduced the protein and free amino acid concentration in both organs. The carbon content in Curcumarhizomes and storage roots was about 0.9 and 2.48 g C plant−1, respectively, at the planting period, and it continuously decreased after planting. N and C stored in the rhizome was assimilated and utilized for root emergence and shoot sprouting [12, 13, 14, 15].

At Curcumashoot sprouting, fertilizer was generally supplied, and N was translocated via roots and leaves. Anatomical study of Curcumaroots and leaves showed the different sizes of cortical cells and the vascular bundle, which were larger in roots than leaves. However, the number of vascular bundles in the roots were lower than in the leaves. The abaxial leaf surface presented less barriers than the adaxial surface [16]. The N-use efficiency of fertilizer (%) via roots was 51–57%, which was higher than that via leaves (7–10%). The research by 15N tracer revealed that N supply during the 1st and 2nd fully expanded leaf stage stimulated leaf growth, and N supply during the 3rd and 4th fully expanded leaf stage was translocate to utilize for flower blooming. N supply with 50 mg N L−1 increased the number of flowers and rhizomes compared with those at 25 mg N L−1 and lack of N supply. After translocation into plant organs, 81–97% of N was assimilated in an 80% ethanol insoluble fraction, mostly by proteins. N supply affected carbohydrate concentration in this plant, since nitrate reduction in roots requires carbohydrates for photosynthesis. The starch and sugar concentration in the rhizome and storage roots was high when Curcumawas grown under N deficiency. The translocation of carbohydrates to both storage organs was related to N deficiency conditions. From the vegetative stage until flowering, C content in leaves increased from 1.37 to 5.31 g C plant−1. The 13C exposure experiment revealed that C was accumulated in leaves during the vegetative stage and flowering, then it translocated to new storage organs (new rhizomes and storage roots) before plant dormancy [13, 15, 17, 18].

3.1.1 Effect of temperature on N uptake

Usually, N uptake and assimilation occur under normal temperature conditions. The optimum temperature for 15N uptake in Curcuma alismatifoliawas 25–35°C [19]. Day and night temperature also affected N uptake and assimilation. The nitrate concentration in leaves, nitrate reductase activity in roots, and total free amino acid content was higher in a plants grown at 30/18°C (day/night temperature) than at 30/25°C. However, a low night temperature reduced the number of shoots per plant and inflorescence quality (spike length and stalk length) in this plant [20, 21].

3.1.2 Response of curcuma to N application

Plant dry matter contains 2–4% N. The most important inorganic forms of N are ammonium (NH4+) and nitrate (NO3), which are converted to an organic form, such as proteins, amino acid, and nucleic acids. There are three steps of N turnover in plants: 1) the conversion of inorganic N to organic N; 2) synthesis of high molecular weight N, such as protein and nucleic acids; and 3) breakdown of nitrogenous macromolecules by hydrolyzing enzymes [1]. Therefore, N supply is essential for growth, flower quality, and yield. However, the response to N was dependent on plant species, soil condition, temperature, and nutrition level. A lack of N reduced growth and development of Curcuma. The number of flowers and rhizome yield also decreased under 0 mg N compared with 25 and 50 mg N [13]. A field experiment was carried out with different N application rates at 3.75, 7.5, 15, 30, and 60 g N/plant, and the results demonstrated that supra-optimal N application at 60 g N/plant reduced plant height, number of shoots/plant, leaf area, and plant dry weight, but leaf N and leaf chlorophyll content increased. The research revealed that the leaf critical N for C. alismatifolia, calculated by the Mitscherlichs model, was 1.51% [21] The optimum fertilizer rate was different depending on the growth stage. The optimum N rates were 234, 937, and 468 kg N/hectares at the vegetative stage (45–75 days after planting), flowering stage (105 days after planting), and before rhizome harvest (135–165 days after planting), respectively (Figure 6) [22].

Figure 6.

Nitrogen application affected flower quality (A) and rhizome yield (B) ofCurcuma alismatifolia(T1–T5 were applied N at 234, 468, 937, 1,875, and 3,750 kg N/hectare). (Ruantip et al. [22]).

3.1.3 N2 fixation and IAA synthesis in curcuma by endophytic bacteria

Nitrogen in the atmosphere that is fixed and converted to the organic form by microorganisms is termed N2 fixation. In Curcuma, N2 fixation by endophytic bacteria was first reported by Ruamrungsri et al. in 2009 [23]. The N-fixing rate varied depending on plant species. Eleven isolates were selected from Curcuma alismatifoliaorgans, such as the leaf, leaf base, and rhizome, and the N-fixing rate was 0.02–4.20 nmole C2H4/106 cells/hr. Seven isolates were derived from leaves, four isolates from the leaf base [23]. Isolates from the leaf base, i.e., ECS 202, identified using 16SrDNA, were Sphingomonas pseudosanguinis(99.2% similarity), ECS 203 was Bacillus drentensisand ECS 204 was Bacillus methylotrophicus. The colonization of these isolates was found in the intercellular spaces of different organs, i.e., roots, leaf base, and rhizome (Figure 7). Re-inoculation with these isolates into Curcumaplantlets derived from in vitro propagation was done by soaking roots in 106 cells/ml of these bacteria. Results showed that plant height, total leaf area (cm2), and N content in roots and leaves of plants inoculated with ECS 203 was higher than the control [24].

Figure 7.

Endophytic bacteria (A) isolate ECS 202 in the rhizome and (B) ECS 203 in the roots ofCurcuma alismatifolia. (photo by Soraya Ruamrungsri).

3.2 Narcissus

Narcissusis a bulbs that has a storage organ that is modified from the leaf base in scales (Figure 8). Generally, the grower grows bulbs in autumn, and flowering occurs in spring. Its roots are an unbranched system that emerges under low temperatures of 9°C. A lack of nitrogen decreased shoot height, root length, chlorophyll intensity, and dry weight of the plant. N-deficient leaves were yellow and small. N concentration was about 12.47 mg gDW−1, which was lower than the control plant (84.09 mgN gDW−1). Sugar content in N-deficient roots was also higher than the control (with N supply), indicating that N metabolism required carbohydrates as an energy source for nitrate reduction and assimilation. Nitrogen was absorbed from fertilizer application in the winter. The N absorbed by roots was translocated to other organs after shoot emergence to promote growth and development. Therefore, N supply was required after root emergence, although the N in the mother bulb was utilized for root growth and shoot sprouting. After shoot sprouting, leaves were the sink organ to derive N from the mother bulb and fertilizer until flower senescence. The uptake of ammonium and nitrate was studied in Narcissususing a 15N tracer. The results showed that at 2 days after fertilization with 1.0 mM of 15NH4+-N compared with 1.0 mM of 15NO3-N and 0.5 mM of 15NH4+-N plus 0.5 mM of NO3-N, Narcissus‘Garden Giant’ roots could more rapidly uptake NH4+-N than NO3-N at 2 days after fertilization, and the rate was equal between NH4+-N and NO3-N for 4–7 days after fertilization. Moreover, the assimilation of N into free amino acids was also different based on the N-form. At 2 days after 15NH4+-N fertilization, N in the roots was incorporated into free amino acids, mostly as glutamine, while asparagine and glutamine were the major assimilation forms of 15NO3-N supply. [25, 26, 27, 28].

Figure 8.

Tunicated bulb of narcissus with young flower inside (A) and unbranched roots (B). (photo by Soraya Ruamrungsri).

3.3 Orchids

The growth of orchids can be presented in two ways, sympodial and monopodial habits, depending on the genus. Some orchids have enlarged bulbous organs at the base of their leaves, called a pseudobulb, with a different shape. These organs store food and mineral nutrition for plant growth and development [29].

3.3.1 Vanda

Vandais a tropical orchid comprised of 40 species. It is an economical orchid with a high export value. The roots of Vandaare aerial roots, freely hanging in the air. Growers use fertilizer applications to control flowering; however, research on plant nutrition in this plant is still rare.

The experiment on N uptake and assimilation in Vandawas carried out within 7 and 30 days after fertilization. The results revealed that plant uptake of 15NO3-N occurred more rapidly than 15NH4+-N or their combination. However, 15N use efficiency was higher in the mixed N source than the sole 15NO3 or 15NH4+ form. N source affected the uptake and translocation of N to various organs, and Vandaprefers NO3-N to NH4+-N. N assimilation in Vandawas different among organs. Alanine distribution was high in leaves and roots at 7 days after feeding. Tyrosine distribution was predominant in leaves, while glutamine distribution was high in stems and roots at 30 days after fertilization [30].

3.3.2 Dendrobium

In Thailand, Dendrobiumis an important orchid genus for export. The main area for Dendrobiumproduction is in the central region of Thailand, such as Ratchaburi, Nakhon, and Pathom provinces. Fertilizer application affected the growth and development of this orchid. A combination of N sources (NO3 and NH4+) promoted the height of psuedobulbs, number of leaves and canes, spike length, and flowering percentage. The N concentration in leaves, roots, and psuedobulbs was 1.24, 0.97, and 0.61%, respectively. Dendrobiumprefers a mixed N-source (ammonium and nitrate) to a sole N source [31].

3.3.3 Phalaenopsis

N level affected the growth of Phalaenopsisorchids. A concentration of 150–200 mg N L−1 increased the inflorescence length, stalk length, and number of flowers per stem. Supplying fertilizer with 21 N-21P2O5-21K2O at 150 mg L−1 once a week to young plants increased the leaf area, leaf dry weight, and N concentration [32]. However, when a high N concentration (200 mg N L−1) was supplied, the K concentration should also be supplied at 200 mg K L−1 to obtain healthy leaves and good quality flowers [33].

3.4 Rose

Rose is the highest potential cut flower in the world market. Rose quality is graded by stem length and flower size. N levels affected shoot height, shoot and flower diameter, flower fresh and dry weight, number of petals per flower, and flower yield. The N concentration in aboveground organs and roots was 19.4 and 20.9 mg N g DW−1 higher, respectively, when the plant was supplied with 200 mg N L−1. The lack of N decreased all quality parameters and showed deficiency symptoms. The optimum N concentration for roses was 200 mg N L−1 plant−1 once a week [34].

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Acknowledgments

This work was partially supported by Chiang Mai University. Thanks to H.M. the King’s Initiative Centre for flower and fruit propagation and the use of a greenhouse and other facilities.

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Conflict of interest

The authors declare no conflict of interest.

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Soraya Ruamrungsri, Kanokwan Panjama, Takuji Ohyama and Chaiartid Inkham (May 29th 2021). Nitrogen in Flowers, Nitrogen in Agriculture - Physiological, Agricultural and Ecological Aspects, Takuji Ohyama and Kazuyuki Inubushi, IntechOpen, DOI: 10.5772/intechopen.98273. Available from:

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