Identification of Native Dendrobium Based on Morphological and Anatomical Characters in Liwa Botanical Garden

Abstract

Orchid is the most popular ornamental plant. One of the many orchid genus collected and known to have high morphological variations in the Liwa Botanical Garden is Dendrobium. But until now many collections have not been identified. This study aims to determine variations and identification of Dendrobium based on characters of morphological and stomata anatomical at Liwa Botanical Garden. Total collections of five Dendrobium accessions were namely CAT140, CAT 144, CAT 271, CAT 274, and IR015. The result showed leaf organs had high variations based on observation of 11 morphological characters. The phenetic relationship showed five accessions of Dendrobium can be classified into 2 main groups formed with a similarity index value of 0.813 based on the Gower similarity value and the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) method. Meanwhile, the results of the observation of 9 anatomical characters on the upper and lower surfaces of the leaves showed accessions IR015, CAT 140, and CAT 274 have stomata only on the lower surface, while CAT 144 has stomata on the upper and lower surfaces. The results of this study are expected to provide basic information in identifying natural orchids and conservation efforts in Liwa Botanical Garden.

1. Introduction

Indonesia is known for its biodiversity of flora and fauna. One species of flora that has a high level of diversity is the orchid plant. The world’s orchid species consist of 20,000 species spread over 900 genera. Orchids have a variety of variations that are located in the morphology, such as the shape of the flower, the number of florets, the size and color of the florets, the diversity of leaf and stem shapes (pseudobulb). One of the most orchid species, namely Dendrobium, with a total of 1500 species spread very widely throughout the world, from Japan, China, India, the Malacca Peninsula, Indonesia, the island of Papua, to Australia. This orchid has a charming flower and its types are also among the most [1, 2, 3, 4, 5, 6].

Dendrobium comes from the words “dendro” (tree) and “bios” (life). Dendrobium means orchid that grows on a living tree. The advantages of Dendrobium because they have a variety of shapes, sizes and colors of flowers. Flowers that have bloomed can last more than 30 days (still in pots) and each stem has more than 20 flower buds arranged neatly and beautifully. When they are adults, Dendrobium can remove more than two flower stems at the same time throughout the year. Easy to adapt so easy to maintain. Dendrobium growth will be optimal at locations less than 400 meters above sea level. Even so, maintenance in areas over 400 m above sea level can still grow and flower, but not optimum. This orchid has a relatively cheap price. This makes many people tempted to hunt orchids because of high economic value [6].

Lampung is one of the places on the island of Sumatra which has a flora conservation area, which is located in the Liwa Botanical Gardens, West Lampung Regency. The Liwa Botanical Garden has many species of orchids that have not yet been identified, given the high increase in exploitation due to economic reasons, this can threaten the existence of natural orchid plants that cause loss of their natural habitat and natural damage resulting in the extinction of existing flora species, especially on plants orchid. Moreover, orchid plants have high economic value because of the beauty of the various forms of flowers. This makes the reason people can just hunt for existing natural orchids. For this reason, the existence of the Liwa Botanical Garden is expected to guarantee the preservation of natural orchid species that can be utilized sustainably. However, until now there are several types of natural orchids that are not known with certainty what natural orchid species exist in the Liwa Botanical Garden [7, 8, 9, 10, 11].

Considering the importance of preserving and preserving orchids in the region, there is a need for further action. One way to do that is by identifying the types of natural orchids, especially Dendrobium species which have a high diversity compared to other orchid species. The identification results will be addressed based on leaf morphology and leaf stomata anatomical structure, given the morphological character is one of the approaches that play an important role in the plant’s taxonomic and systemic basis. This study aims to determine variations in morphological characters and phenetic relationships and identification of Dendrobium based on morphological characters in the Liwa Botanical Garden. The results of this study are expected to be basic information in the identification of natural orchids and conservation efforts in the Liwa Botanical Garden.

2. Identification of stomata morphological characters

Sample collection was carried out on Dendrobium leaves in the Liwa Botanical Garden. Overall, the sample accession is a native orchid of flora from Lampung. All samples were tabulated and documented with photos. The sample collection stage was conducted in December 2019–February 2020 at the orchid green house in the Liwa Botanical Garden. Dendrobium samples were chosen based on orchid data that could not yet be identified. Collection results obtained 5 accessions of Dendrobium samples with sample codes CAT140, CAT 144, CAT 271, CAT 274, and IR015 (Table 1). Overall, the sample accession is a native natural orchid of flora from Lampung.

No. Acc.	Species	Origin location
CAT140	Dendrobium sp.	Bukit Barisan Selatan National Park
CAT144	Dendrobium sp.	Seminung Forest
CAT271	Dendrobium sp.	Bukit Barisan Selatan National Park
CAT274	Dendrobium sp.	Bukit Barisan Selatan National Park
IR015	Dendrobium sp.	Bukit Barisan Selatan National Park

Table 1.

List of accessions of Dendrobium samples in the Liwa Botanical Garden.

The morphological identification research phase was carried out by direct observation when sampling in the field. Leaf morphology characters identified included leaf shape, length (P) and width (L) of leaf, leaf tip shape, leaf cross section, leaf arrangement, leaf edge shape, leaf surface texture, leaf symmetry, and leaf sitting [12, 13].

Based on observations of morphological characters in the field, orchid plants have a high variation. These variations were found in habitus, pseudobulb, leaves, and flowers [13]. In this research the character of the flower is not done because the variation in habitus is seen in plant height, which ranges from 50–125 cm. Plant height can be categorized into 2, namely ≤ 100 cm (short) and> 100 cm (height) (Figure 1).

Figure 1.

Habitus accession of Dendrobium samples in the Liwa Botanical Garden: (A) CAT 274, (B) CAT 144, (C) CAT 140, (D) IR 015, and (E) CAT 271.

Leaves of Dendrobium have most varied organs based on field observation, (Table 2). Variation of leaf shape i.e. shape, length (P) and width (L), tip shape, cross section, arrangement, edge shape, surface texture, symmetry, and sitting of leaf [14].

Table 2.

Leaf type of accession of Dendrobium samples in the Liwa Botanical Garden [14].

Bar = 1 cm.

Five accessions of Dendrobium from Liwa Botanical Garden showed a different morphological characterization of leaves, i.e. cross-sectional characteristics and sitting of leaf. In the sample with accession number CAT 274, CAT 140, IR 015 and CAT 271 the leaf cross section is zigomorphic (symmetry), whereas on accession number CAT 144 the leaf cross section is tight. In addition, intermittent leaf sitting was found in CAT 274 accession number, IR 215 and CAT 271, in contrast to samples with CAT accession number 144 characters of intermittent leaf sitting and meeting almost filled the plant stem and CAT 140 characters sat leaf intermittent intermittent interspersed and tightly located near the end of the stem [14].

Although the morphological characterization of the leaf shape was the same in all samples, namely the lanceolate/javelin shape, the length and width of the leaves differed from one sample to another. In CAT 274 samples (P: 4.5 cm and L: 1 cm), CAT 144 samples (P: ± 1.7 cm and L: 0.5 cm), CAT 140 samples (P: 9.5 cm and L : 1.5 cm), IR 015 samples (P: 8 cm and L: 2 cm), and CAT 271 samples (P: 8.5 cm and L: 1.5 cm).

Analysis of phenetic was done using cluster analysis and principal component analysis (PCA) methods. The first step is the scoring morphological character using cluster analysis, then calculated the value of Gower similarity (Gower’s General Similarity) which results in a matrix of similarity between accessions. Data of matrix similarity using the UPGMA method was done by agglomerative hierarchial clustering, then the result was displayed on dendrogram.

Samples that have a longer leaf length morphological character CAT 140 (P: 9.5 cm and L: 1.5 cm), IR015 (P: 8 cm and L: 2 cm) and CAT 271 (P: 8.5 cm and L: 1.5 cm) will have a higher plant height habitus compared to samples that have shorter leaf morphological characters in CAT 274 samples (P: 4.5 cm and L: 1 cm) and CAT 144 (P : ± 1.7 cm and L: 0.5 cm). Furthermore, there is also a striking difference in the morphological character of the lowest plant leaves, namely in CAT 144 (P: ± 1.7 cm and L: 0.5 cm). Other character differences also have the lowest plant height habitus and have a thicker leaf thickness than the others. The result of morphology character identification of the Dendrobium leaves from Liwa Botanical Garden is presented in Table 3.

Morphology character	CAT 274	CAT 144	CAT 140	IR 015	CAT 271
Shape	Shape of lanceolate/eye javelin	Shape of lanceolate/eye javelin	Shape of lanceolate/eye javelin	Shape of lanceolate/eye javelin	Shape of lanceolate/eye javelin
Length (P) and width (L)	P: 4.5 cm and L: 1 cm	P: ±1.7 cm and L: 0.5 cm	P: 9.5 cm and L: 1.5 cm	P: 8 cm and L: 2 cm	P: 8.5 cm and L: 1.5 cm
Tip shape	Taper/pointed/sharp to the tip	Taper/pointed/sharp to the tip	Taper/pointed/sharp to the tip	Taper/pointed/sharp to the tip	Taper/pointed/sharp to the tip
Cross section	Zigomorph (symmetry)	Double	Zigomorph (symmetry)	Zigomorph (symmetry)	Zigomorph (symmetry)
Arrangement	Double	Double	Double	Double	Double
Edge shape	Frayed (flat)	Frayed (flat)	Frayed (flat)	Frayed (flat)	Frayed (flat)
Surface texture	Hairless (smooth)	Hairless (smooth)	Hairless (smooth)	Hairless (smooth)	Hairless (smooth)
Symmetry	Symmetry	Symmetry	Symmetry	Symmetry	Symmetry
Sitting	Intermittent	Intermittent and close to almost meet the stems of plants	Intermittently intermittent and close to the end of the stem	Intermittent	Intermittent

Table 3.

Leaf variation of morphology character identification result of accession of Dendrobium samples from Liwa Botanical Garden.

Based on Table 3, it is known that most of the accessions of Dendrobium samples in the Liwa Botanical Garden show the same morphological variation in the leaves:

1. The shape of lanceolate/javelin-shaped leaves.

2. The shape of the leaf tip is sharp/pointed/sharp to the tip.

3. Dual leaf arrangement.

4. The edge of the leaf is frayed (even).

5. Leaf surface texture is bald (smooth).

6. Symmetry of leaves in the form of symmetry.

In other characters, namely the form of pseudobulb and the place of growth, it is known that the entire accession of Dendrobium samples did not form pseudobulb and epiphytic antibiotic types. Character types of habitats in general all Dendrobium have the same type, epiphytes, according to natural conditions where the sample collection of the Liwa Botanical Garden is a natural orchid taken from its natural habitat, such as the Bukit Barisan Selatan National Park and Seminung Forest which has low humidity (dry) at an altitude of 800–900 m above sea level. Epiphytic orchids grow in their natural habitat requires the intensity of indirect sunlight. In accordance with the type of growth attached to the host [13].

2.1 Phenetic analysis

Phenetic analysis on five accession of Dendrobium is done through cluster analysis and principal component analysis (PCA) methods. The first steps, scoring of the morphological character using cluster analysis, then calculated the Gower similarity value (Gower’s General Similarity) between five accessions using matrix of similarities. Then UPGMA methods to calculate the similarity matrix data using clustering of agglomerative hierarchial. The dendrogram results of analysis cluster of five Dendrobium accessions based on the morphological characters are presented in Figure 2.

Figure 2.

Dendrogram five Dendrobium accession of samples from Liwa Botanical Garden using UPGMA.

Grouping the sample based on the level of similarity between accessions calculated using the gower coefficient formula and UPGMA was chosen for the clustering technique to produce a dendogram showing 2 main groups formed with a similarity index value of 0.813 marked as group A and group B. Group A consists of CAT 144 which has a distinguishing character that distinguishes from group B, namely the cross section of the double leaf character (Figure CAT 144). Group B consists of CAT 140, CAT 271, IR 015, and CAT 274 which have symmetrical cross-section characters (Figure CAT 140, CAT 271, IR 015, and CAT 274). Group B is divided into 2 sub-groups with a similarity index value of 0.861 marked with B1 and B2 on the dendogram. Characters that show the difference between the two, namely the ratio of the length and width of the leaf and leaf sitting. CAT 140 consists to subgroup B1, meanwhile CAT 271, IR 015, and CAT 274 consist to subgroup B2. Subgroups B2 are divided into 2 based on differences in leaf length and width ratios namely B2a and B2b. IR 015 and CAT 274 in one group B2b with a similarity level of 100% were indicates the same type. Based on the PCA values, it can be seen that characters have a large influence on grouping are the ratio of length and width (PLD), cross section (PMD), and sitting (DKD). Variability of orchid leaf characters can be possible due to the hybridization and outcrossing processes.

3. Identification of stomata anatomical characters

The research stage of leaf stomata identification was carried out by direct observation using a miscropcope shortly after sampling in the field. The anatomical characters of leaf stomata identified include the average number of stomata, average length of stomata, average stomata width, average number of epidermis, average length of epidermis, average epidermal width, stomata index, stomata type, shape epidermis on the upper and lower surfaces of the leaves [13].

The epidermis is a system of cells, varying in structure and function that protects the primary plant body. The leaf epidermis is the outermost layer of cells, generally only one layer. In the leaf epidermis, there are usually epidermal derivatives in the form of stomas (plural: stomata). A stoma is a gap in the epidermis that is bounded by two special epidermal cells, namely the covering cell that functions to widen or narrow the gap. The stoma is surrounded by cells that can be the same or different from other epidermal cells called neighboring cells [13].

In this study, observations were made on 4 types of Dendrobium, namely Dendrobium IR015, Dendrobium CAT 140, Dendrobium CAT 144, and Dendrobium 274. Observations were made on the upper and lower surfaces of leaves (Table 4).

No.	Parameter	IR 015	CAT 140	CAT 144	CAT 274
1.	Leaf upper surface
	Average number of stomata	—	—	2.80	—
	Average length of stomata (μm)	—	—	2.45	—
	Average stomata width (μm)	—	—	2.17	—
	Average number of epidermis	29	41	45	42.8
	Average epidermal length (μm)	5.22	5.49	4.31	4.64
	Average epidermal width (μm)	4.22	2.79	2.65	2.88
	Stomata index (%)	—	—	5.86	—
	Stomata type	—	—	Tetracytic (1 stomata surrounded by 4 neighboring cells)	—
	Epidermis shape	Irregular, pentagonal, hexagonal	Irregular, pentagonal	Irregular, quadrilateral, pentagonal	Irregular, quadrilateral, pentagonal
2.	Leaf Lower Surface
	Average number of stomata	5.2	2.50	2.50	3.4
	Average length of stomata (μm)	2.75	2.78	2.33	2.57
	Average stomata width (μm)	1.96	2.45	2.07	1.82
	Average number of epidermis	32.2	30.75	43.50	42.2
	Average epidermal length (μm)	3.54	5.13	4.42	3.74
	Average epidermal width (μm)	2.72	3.03	3.06	2.45
	Stomata index (%)	13.90	7.52	5.43	7.46
	Stomata type	Tetracytic (1 stomata surrounded by 4 neighboring cells)	Tetracytic (1 stomata surrounded by 4 neighboring cells)	Tetracytic (1 stomata surrounded by 4 neighboring cells)	Tetracytic (1 stomata surrounded by 4 neighboring cells)
	Epidermis shape	Irregular, pentagonal, hexagonal	Irregular, pentagonal	Irregular, quadrilateral, pentagonal	Irregular, quadrilateral, pentagonal

Table 4.

Anatomical characters on the upper and lower surfaces of leaves.

Based on Table 4, it is known that the types of IR015, CAT 140, and CAT 274 have stomata only on the lower surface, while CAT 144 has stomata on the upper and lower surfaces. This difference is due to the position of the leaves attached to the stem at CAT 144 forming an angle of 45°C, while the others open horizontally. This causes the top and bottom sides to be the same. The anatomical characters on CAT 144 on the upper and lower surfaces of the leaves, such as the number of stomata, length of stomata, width of stomata, number of epidermis, length of epidermis, width of epidermis, index of stomata are not much different. Stomata are kidney-shaped, and belong to the tetracytic type, namely in the form of stomata surrounded by 4 neighboring cells. In IR015, CAT 140, and CAT 274 the upper surface of the leaves is composed only of the epidermis which is mostly irregular and pentagonal in shape. The highest number was in CAT 274 because the epidermis was smaller than IR015 and CAT 144.

On the lower leaf surface, it is known that the number of stomata at IR015 is the highest and the number of epidermis is the least, so that the stomata index is the largest. The stomata index looks the largest because the stomata index shows the number of stomata divided by the number of stomata plus the number of epidermis and multiplied by 100%. The types of stomata in all types are the same, namely tetracytic in the form of stomata surrounded by 4 neighboring cells. The stomata are kidney-shaped and the epidermis is irregular, pentagonal, and hexagonal in shape.

4. Conclusions

Five accessions of Dendrobium from Liwa Botanical Garden were identification based on morphological characters and phenetic relationships. The result of analysist 11 morphological characters showed leaf of Dendrobium have high variations. The phenetic relationship showed five accessions of Dendrobium from Liwa Botanical Garden can be classified into 2 main groups formed with a similarity index value of 0.813. The morphological characters that have a large influence on grouping are the ratio of length and width, cross section, and sitting of leaf based on PCA values. Variability of Dendrobium leaf characters can be possible due to the hybridization and outcrossing processes. The resulting phenetic dendrogram topology is supported by the morphological character classification. The results of the observation of 9 anatomical characters on the upper and lower surfaces of the leaves indicate that the leaf organs have high variations. Accessions IR015, CAT 140, and CAT 274 have stomata only on the lower surface, while CAT 144 has stomata on the upper and lower surfaces. This difference is due to the position of the leaves attached to the stem at CAT 144 forming an angle of 45̊C, while the others open horizontally. IR015, CAT 140, and CAT 274 the upper surface of the leaves is only composed of epidermis which is mostly irregular and pentagonal in shape. The highest number was in CAT 274 because the epidermis was smaller than IR015 and CAT 144. The types of stomata in all types were the same, namely tetracytic in the form of stomata surrounded by 4 neighboring cells. The stomata are kidney-shaped and the epidermis is irregular, pentagonal, and hexagonal in shape.

Acknowledgments

The author thanks to Lembaga Penelitian dan Pengabdian Masyarakat (LPPM), Lampung University was funded this research through the DIPA BLU 2020 Grant with contract number 1492/UN26.21/PN/2020. Thank you to the Liwa Botanical Garden who facilitated the research based on collaboration program with Department of Biology, Faculty of Mathematics and Natural Science, Universitas Lampung.