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ISSN : 1225-5009(Print)
ISSN : 2287-772X(Online)
Flower Research Journal Vol.21 No.4 pp.162-171
DOI : https://doi.org/10.11623/frj.2013.21.4.32

Anatomical and Morphological Variation in Dracaena reflexa ‘Variegata’ Grown in Different Organic Potting Substrates

Adnan Younis1,2*, Atif Riaz1, Muhammad Irfan Siddique1, Ki-Byung Lim2, Yoon-Jung Hwang3, Muhammad Asif Khan1
1Institute of Horticultural Sciences, University of Agriculture, Faisalabad, 38040, Pakistan
2Department of Horticultural Science, Kyungpook National University, Daegu 702-701, Korea
3Department of Life Science, Sahmyook University, Seoul 139-742, Korea
Received 3 September 2013; Revised 7 November 2013; Accepted 24 December 2013

Abstract

Potting media are an integral part of potted plantsproduction system, formulated by a mixture of various rawmaterials to act as a substrate for plant support and sourceof nutrition. There is a wide range of potting media available,which are used for quality production of high-value plantsworldwide. In this study, quality assessment of Dracaenaplants grown in different potting media like: mushroomcompost, peat, sand, farmyard manure, coconut coir, andleaf compost in different combinations were carried out. Amixture of sand, mushroom compost, coconut coir, and peatproved to be the best, by promoting root and shoot growth,leaf area, fresh and dry weights of root and shoot, and alsoimproved overall quality of the plant. Media containinggarden soil alone or a mixture of sand and leaf compostproduced the lowest quality of plants with considerablereduction in most of the growth parameters. Anatomicalparameters showed weak relation to media composition ascompared to other morphological features. The best mediumwas made with sand, mushroom compost, coconut coir,peat, that produced plants with thick epidermis and largerpith cells, but thin endodermis and smaller metaxylemvessels in their roots. As moisture availability was sufficientenough in this medium combination, the development ofwater storing tissue may not contribute significantly. However,epidermis can play a decisive role in protecting roots fromexternal environmental hazards.

0051-01-0021-0004-4.pdf1.92MB

Introduction

 Dracaena reflexa ‘Variegata’ is a member of family Asparagaceae (also placed in the Agavaceae, Convallariaceae, Dracaenaceae, Liliaceae, or Ruscaceae), native to Africa (Madagascar). It is widely grown ornamental potted plant under subtropical and tropical climates throughout the world. ‘Variegata’ is due to its variegated forms which make it unusual and excellent specimen plant that can be used indoor foliage plant for interiorscape in homes, offices, hotels, airport lounges, and shopping malls (Jones and Luchsinger 1986). Despite its irregular multi-stem growth habit it is popular for the formal landscape as bedding plant that may grow up to 10 feet tall or more but as interior-plant it grows up to 5 feet. Its leaves are narrow and of lanceolate to elliptic shape having parallel veins of deep green color with yellow lime-green to creamy margins. In Madagascar, traditionally, D. reflexa were grown in kitchen garden for medicinal purposes to cure malarial symptoms, diarrhea, poisoning, dysentery, dysmenorrhoea, and was considered useful as a hemostatic and antipyretic agent (Randrianarivelojosia et al. 2003). 

 Commercially, different potting mixes are available for floriculture production system usually made up of different organic components like peat as well as mineral components such as perlite, calcined clay, and sand. Some alternative raw materials like, coir (shredded coconut husks), leaf compost, mushroom compost, municipal compost, and farm yard manure can be used as supplementary nutritional source in potting media. Selecting proper growing medium is prerequisite for optimum growth and development of potted plants (Younis et al. 2009). It supplies the basic nutrients and essentials support for plants throughout its life cycle. Generally, cuttings and seedlings are grown in different types of soil, due to which root zone is greatly affected by the chemical and physical properties of the growing medium used (Shah et al. 2006; Tariq et al. 2012). A potting medium is generally comprises of liquid, solid, and gaseous components. The solid part constitutes 33-50% of the media volume, whereas the 2nd portion liquid entails of water, dissolved nutrients, and organic ingredients. The 3rd portion is the gaseous that contains oxygen and carbon dioxide, which constitutes 50-70% (v/v) of the potted medium. Presence of oxygen proved to be very significant for root growth in the medium and at least 12% concentration maintained for roots reported to be excellent for vigorous growth and deep root system (Gil et al. 2012; Yasmeen et al. 2012).

 Variety of growing media has been used in the past for successful cultivation of horticultural plants by many researchers, e.g., for Vinca rosea ‘Victory’ (Khattak et al. 2011) mushroom compost proved to be the most successful potting media. For Dahlia hortensis ‘Figaro’ pot production, municipal compost gave excellent results (Tariq et al. 2012), whereas, Jayasinghe (2012) found composted sewage sludge as a better alternative potting medium for lettuce cultivation. In Zinnia elegans cv. ‘Blue Point’, a combination of silt, coconut compost, and leaf manure was found to be the best source of NPK (Riaz et al. 2008). 

 Anatomical structure is a representative of habitat conditions in which a plant grows. In particular, if a plant is facing stressful environmental conditions, specific anatomical changes enable it to thrive well through these adverse conditions (Kovacic and Nikolic 2005). Generally leaves are more responsive to stressful environment, and anatomical changes can serve as diagnostic markers to different environments. Under unfavourable growing conditions, tissues such as mesophyll parenchyma, sclerenchyma, and vascular tissue can play a decisive role in the growth and survival of a plant species (Bonnet et al. 2004; Hameed et al. 2012). Plants have different responses for their morphological and anatomical features under different types of root zones. Therefore, the present study was designed to check the performance of various combination of growing media on the growth, morphology, and anatomy of D. reflexa ‘Variegata’ since no such work have been done previously on this species on these aspects. 

Materials and Methods

Plant material and potting media

 The experiment was carried out in the Floriculture area, Institute of Horticultural Sciences, University of Agriculture, Faisalabad to investigate the influence of different selected potting media on the growth and anatomy of D. reflexa ‘Variegata’. Earthen pots (24 cm in diameter) were used for the plantation of shoot cuttings (15 cm long), which were purchased from a local commercial nursery. Plants were kept in the greenhouse at 25 ± 2℃ for six months to grow and then growth data were collected fortnightly. 

 Treatment combinations were made by taking equal quantities. The combinations were: Garden Soil (GS, control), Soil + Coconut coir (S + CC), Soil + Farm yard manure (S + FM), Soil + Leaf com-post (S + LC), Soi + Mushroom compost (S + MC), Soil + Peat (S+P), Soil + Mushroom compost + Coconut coir (S + MC + CC), Soil + Mushroom compost + Farm yard manure (S + MC + FM), Soil + Mushroom compost + Leaf compost (S + MC + LC), Soil + Peat + Coconut coir (S + P + CC), Soil + Peat + Farm yard manure (S + P + FM), Soil +Peat + Leaf compost (S + P + LC), Soil + Mushroom compost + Coconut coir + Peat (S + MC + CC + P), Soil +Mushroom compost + Farm yard manure + Peat (S + MC + FM + P), and Soil +Mushroom compost + Leaf compost + Peat (S + MC + LC + P). Ten plants were used for each treatment and treatment was replicated three times to get precise data. Data for morpho-anatomical features and overall quality were recorded at the end of the experiment.

Analysis of Media

Water Holding Capacity (Saturation percentage)

 The saturated soil paste was set as demonstrated by U.S. Salinity Lab. staff (1954). It was oven dried at 100℃ till the constant oven dried weight was detected.

 Saturation percentage was calculated by the formula:

 

pH

 The pH was recorded through a digital ion analyser (pH meter). The saturated soil paste was made by adding 10 g of soil with 20 mL distilled water and kept for 60 min. The pH electrodes were inserted into the soil paste and was raised and lowered repetitively until pH reading got stable (U.S. Salinity Lab. Staff 1954).

Estimation of N, P, K

 Total nitrogen was estimated by using Kjeldahl’s apparatus (Timberline Instruments, USA). Conversion of sample’s nitrogen into NH4+ form was carried out through digestion with H2SO4 (concentrated) and digestion mixture. After cooling the contents were shifted to 100 mL flask (Kinax, USA). The distillation process was done in a micro Kjeldahl apparatus using boric acid and methyl red as an indicator. The titration was carried out with standard H2SO4 to calculate total nitrogen in soil sample (Jackson 1962).

 Available phosphorus was estimated by taking 1.25 g sample of each medium was collected and 25 mL of extracting solution was added into it and shake for 30 min and then filtered. 1 mL of filtered mixture was collected in flask and DD water (3 mL) was put, then 1 mL of colour developing reagent was added and stirred. It was kept for 15 min and reading was taken at 880 mU on the Spectrophotometer (model spectrum 21).

 Phosphorus was calculated by using the formula (Watanable and Olsen 1965), 

 

 For estimation of potassium the flame photo metric method was used. Meq/1 of K+=TMeq/1 of K+ by calibration curve × 50 mL of sample (U.S. Salinity Lab. Staff 1954).

Anatomical Analysis

 Permanent double-strained (safranin and fast green) slides of root, shoot and leaf were prepared for anatomical studies as adopted by Ruzin (1999). For root anatomy 2 cm slice from the thickest root, for shoot anatomy 2 cm slice from the top internode and for leaf anatomy 2 cm slice from the leaf centre including midrib were selected. Camera photographs were taken by Carl-Ziess camera microscope (LLC, USA). Thickness and area of dermal, mechanical, parenchymatous and vascular tissues were recorded during the experiment.

 The experiment was laid out in factorial completely randomized design (CRD-Factorial). Data were analyzed statistically using ANOVA techniques (Steel et al. 1997) and means were compared by using Tukey’s Test.

Results

Chemical and Physical Properties of Soil

 Soils physico-chemical characteristics are presented in Table 1. The highest water holding capacity was found in S + MC + FM + P whereas, water holding capacity was the minimum in GS. S + MC + FM + P showed the lowest pH value and the highest pH value was observed in S + P + FM, which was closely followed by S + P. Highest nitrogen was present in S + MC + FM + P, which was followed by S + P, while GS had lowest available nitrogen. Nitrogen is established mandatory plant nutrient and it is apparent from present findings that different media combinations varied in total nitrogen contents. Phosphorus is also another essential nutrient for vigorous growth of dracaena plants. The highest phosphorus percentage was recorded in S + MC + FM + P, whereas it was the minimum in GS. S + MC + FM + P showed the highest potassium, which was followed by S + P. The minimum potassium was recorded in GS.

Table 1. Physico-chemical properties of different potting media used for cultivation of Dracaena reflaxa ‘Variegata’.

Morphological Parameters

 The results demonstrated significant superiority of height in S + MC + LC + P, which was followed by the height in S + MC + CC + P medium and GS medium, while S + FM showed the shortest plants (Fig. 1). Maximum number of roots was produced by medium containing S + MC + CC + P while, GS medium showed the lowest value as compared to other media. The combination of S + MC + CC + P in a medium gave the highest root length, which was followed by S + P medium and medium with GS alone showed the lowest value of root length as compared to other media (Table 2). Number of leaves per plant was the maximum in media containing S + MC + CC + P, while the minimum of this parameter was recorded in media GS (Table2). It was noted that S + MC + CC + P medium proved the best for leaf area, which was followed by S + P medium. Medium containing GS showed the smallest leaves. 

Fig. 1. Morphological characteristics of Dracaena cultivated in A, sand + coconut coir + mushroom compost + peat; B, sand + peat; C, sand + mushroom compost + farmyard manure; D, garden soil.

Table 2. Morphological characteristics of Dracaena reflaxa ‘Variegata’ cultivated in different growth media.

 Medium containing S + MC + CC + P produced the maximum root fresh weight, closely followed by S + P medium regarding this parameter. The GS medium resulted in the minimum root fresh weight (Table 2). The maximum fresh weight of shoot was recorded in S + MC + CC + P medium, which was followed by S + P medium, whereas the minimum was recorded in GS medium (Table 2). The medium containing S + MC + CC + P showed the maximum dry weight of root, closely followed by that recorded in S + P medium. The minimum root dry weight was recorded in GS medium, which was used as a control (Table 2). The medium containing S + MC + CC + P showed the maximum shoot dry weight, which was followed by that containing S + P. The minimum dry shoot weight was recorded in GS and S + LC growing media (Table 2). Overall plant quality was the best in S + MC + CC + P and S + P media, which was followed in S + MC + LC + P medium, whereas plants growing in GS medium showed overall poor quality (Table 2). 

Root Anatomy

 Epidermal thickness was the maximum in plants of S + MC + LC medium, closely followed in plants of S + CC + MC + P medium, whereas, the minimum of this parameter was seen in plants of GS medium (Fig. 2). Epidermal cell area, in contrast, was the maximum in plants growing in S + LC medium, which was followed by plants of S + CC + MC + P medium, and the minimum cell area was recorded in plants of S + MC + LC + P medium (Table 3).

Fig. 2. Transverse sections of root of Dracaena cultivated in A, garden soil [multi-layered epidermis (black arrow), thin wall endodermis with wide metaxylem vessels (white arrow)]; B, sand + coconut coir [multi-layered epidermis (black arrow), thin wall endodermis with wide metaxylem vessels (white arrow)]; C, sand + farmyard [narrow metaxylem vessels (white arrow)]; D, sand + eaf compost [two layered epidermis with large cortical region (black arrow) narrow metaxylem vessels (white arrow)]; E, sand + mushroom compost [two layered epidermis (black arrow), thin wall endodermis with slight sclerification in pith region (white arrow)]; F, sand + peat [two layered epidermis (black arrow)]; G, sand + mushroom compost + coconut coir [irregular shaped epidermis (black arrow), slight sclerification in endodermis and small metaxylem vessels (white arrow)]; H, sand + mushroom compost + farmyard manure [irregular shaped epidermis (black arrow), slight sclerification in endodermis and small metaxylem vessels (white arrow)]; I, sand + mushroom compost + leaf compost [two layered smaller epidermal cells (black arrow), sclerified endodermis with many metaxylem vessels (white arrow)]; J, sand + peat + coconut coir [two layered smaller epidermal cells (black arrow), sclerified endodermis with many metaxylem vessels (white arrow)]; K, sand + peat + farmyard manure [two layered epidermal cells with thickly packed cortical parenchyma cells (black arrow), sclerified endodermis with large metaxylem vessels (white arrow)]; L, sand + peat + leaf compost [two layered epidermal cells with thickly packed cortical parenchyma cells (black arrow), sclerified endodermis with large metaxylem vessels (white arrow)]; M, sand + coconut coir + mushroom compost + peat [multi-layered epidermal cells with thin wall cortical parenchyma (black arrow), sclerified endodermis with many metaxylem vessels (white arrow)]; N, sand + mushroom compost + farmyard manure +peat [multilayered epidermal cells with thin wall cortical parenchyma (black arrow), sclerified endodermis with many metaxylem vessels (white arrow)].

Table 3. Root anatomical characteristics of Dracaena reflaxa ‘Variegata’ cultivated in different growth media.

 Cortical region thickness in roots was the maximum in plants of S + MC + LC medium, which was closely followed by that recorded in plants of S + CC + MC medium (Fig. 3). The minimum of this character was recorded in plant growing in GS medium. Cortical cell area, however, was the maximum of plants growing in S + LC and S + MC media, and the minimum in those growing in S + MC + FM + P medium. The largest endodermis cells were recorded in plants provided with S + LC medium, which was followed by those with S + P + FM medium, and the smallest cells were noted in plants of S + MC + LC + P medium. Sclerification in endodermis was the most prominent in plants of S + LC + MC + P, but plants growing in S + FM + MC + P, S + CC + MC + P, and S + P + LC media also showed distinctive scarification (Table 3).

Fig. 3. Transverse sections of root of Dracaena cultivated in A, garden soil [multi-layered epidermal cells with small cortical cells (black arrow), sclerified endodermis with many metaxylem vessels (white arrow)]; B, sand + coconut coir [multi-layered epidermal cells with small cortical cells (black arrow), sclerified endodermis with many metaxylem vessels (white arrow)]; C, sand + farmyard manure [multi-layered epidermal cells with large cortical cells (black arrow), sclerified endodermis with many metaxylem vessels (white arrow), vascular region (black arrow head)]; D, sand + leaf compost [multi-layered epidermal cells with small cortical cells (black arrow), sclerified endodermis with many metaxylem vessels (white arrow)]; E, sand + mushroom compost [multi-layered epidermal cells with large cortical cells (black arrow), sclerified endodermis (white arrow)]; F, sand + peat [multi-layered epidermal cells with large cortical cells (black arrow), sclerified endodermis (white arrow)]; G, sand + mushroom compost + coconut coir [sclerified endodermis and vascular region with large metaxylem (white arrow)]; H, sand + mushroom compost + farmyard manure [multi-layered small epidermal cells with small cortical cells (black arrow), sclerified endodermis and vascular region with large metaxylem (white arrow)]; I, sand + mushroom compost + leaf compost [multi-layered epidermal cells with densely packed cortical cells (black arrow), sclerified endodermis and vascular region (white arrow)]; J, sand + peat + coconut coir [multi-layered epidermal cells with densely packed cortical cells (black arrow), sclerified endodermis and vascular region (white arrow)]; K, sand + peat + farmyard manure [slight sclerification in endodermis (black arrow), dense sclerified vascular region (white arrow)]; L, sand + peat + leaf compost [irregular shaped epidermal cells (black arrow), thin wall cortical cells (yellow arrow)]; M, sand + coconut coir + mushroom compost + peat [multilayered epidermal cells (black arrow), sclerified endodermis (white arrow), vascular region with many meta xylum (black arrow head)]; N, sand + mushroom compost + farmyard manure + peat [multi-layered epidermal cells (black arrow), sclerified endodermis (white arrow)]; O, sand+ mushroom compost + leaf compost + peat [multi-layered epidermal cells (black arrow), sclerified endodermis (white arrow), slight sclerification in pith region (black arrow head)]; P, sand [multi-layered epidermal cells (black arrow), sclerified endodermis (white arrow)].

 Vascular region thickness was the maximum in plants of S + MC + LC and S + MC media, and the minimum in that of S + MC + LC + P medium. The widest metaxylem vessels were recorded in plants growing in S + FM medium, which was closely followed in plants of S + P medium. The narrowest vessels were seen in plants of S + MC + FM+P medium. Phloem area was the maximum in growing in S + MC + LC and the minimum in those of S + P + LC medium. Larger vascular tissues with large vessels and phloem region can be more efficient in translocation of water, solutes and photosynthates. A prominent sclerification in vascular region was recorded in plants of S + LC + MC + P, but in those of S + FM + MC + P, S + PC + MC + P, and S + P + CC also showed high amount of sclerification. Plant provided with GS growth medium did not show any sclerification at all (Table 3).

 The pith cell area was the maximum in plants growing in S + MC + LC medium, where plants of S + P + FM showed the second best of this parameter. The minimum area was recorded in plants grown in S +MC + FM+ P medium (Table 3).

Leaf Anatomy

 Leaf thickness was the maximum in plants growing in S + LC medium, closely followed by the plants in S + CC + MC medium. The thinnest leaves were recorded in plants of S + CC medium (Fig. 4). Plant growing in S + P medium showed the maximum adaxial epidermal cell area, which followed by those in S + P + FM medium. However, plants growing in S + P + LC and S + MC + LC + P media showed much reduced adaxial epidermal cells (Table 4). Medium S + LC showed the largest abaxial epidermal cell area, which was followed by S + P. The smallest epidermal cells were recorded in media containing S + FM + MC + P and S + MC + LC + P (Table 4). The cortical cell area was the maximum in S + FM + MC + P medium. The media containing S + P + CC, S + MC + CC, and S + P + FM also had a large cortical cell as compared to those recorded on other media. The minimum of this character was recorded in plants growing in GS medium (Table 4).

Fig. 4. Transverse sections of leaf of Dracaena reflaxa ‘Variegata’ cultivated in A, garden soil [thick leaves with large vascular bundles (black arrow), narrow metaxylem vessels (white arrow)]; B, sand + coconut coir [thick leaves with large vascular bundles (black arrow), narrow metaxylem vessels (white arrow)]; C, sand + farmyard manure [thin leaves with large vascular bundles (black arrow), few narrow metaxylem vessels (white arrow)]; D, sand + fleaf compost [thick leaves with small vascular bundles (black arrow), many metaxylem vessels (white arrow)]; E, sand + mushroom compost [thick leaves with sclerified vascular bundles (black arrow), many metaxylem vessels (white arrow)]; F, sand + fpeat [vascular bundles with many metaxylem vessels (black arrow)]; G, sand + fmushroom compost + fcoconut coir [thin leaves (black arrow), highly sclerified vascular bundles (white arrow)]; H, sand + fmushroom compost + ffarmyard manure [thick leaves (black arrow), highly sclerified vascular bundles (white arrow)]; I, sand + f mushroom compost + fleaf compost [leaves with large sclerified vascular bundles (black arrow), large phloem area (white arrow)]; J, sand + fpeat + fcoconut coir [leaves with thick epidermal layer (black arrow), sclerified vascular bundles (white arrow)]; K, sand + fpeat + ffarmyard manure [leaves small sclerified vascular bundles (black arrow)]; L, sand + fpeat + feaf compost [vascular bundles with few wide metaxylem vessels (black arrow)]; M, sand + fcoconut coir + fmushroom compost + fpeat [thick leaves with highly sclerified vascular bundles (black arrow), many metaxylem vessels (white arrow)]; N, sand + fmushroom compost + ffarmyard manure + fpeat [thick leaves with highly sclerified vascular bundles (black arrow), many metaxylem vessels (white arrow)].

Table 4. Leaf anatomical characteristics of Dracaena reflaxa ‘Variegata’ cultivated in different growth media.

 Plants growing in S + MC medium showed the largest vascular bundle, which was followed by the plants growing in S + FM + MC + P medium. Plants growing in medium containing S + CC had the smallest vascular bundles (Table 4). Metaxylem in plants provided with S + MC + LC and S + MC media were the largest, whereas narrow vessels were recorded in plants growing in S + MC + LC + P medium. Phloem area, in contrast, was the maximum in media containing S + MC and S + CC + MC. Its minimum was recorded in plants growing in S + MC + C medium (Table 4). Pearson’s correlation coefficient (r) between soil physico-chemical and plant morpho-anatomical characteristics was calculated. Plant height did not show any correlation with soil physico-chemical characteristics. However, water holding capacity, and available N and P in medium correlated positively and significantly with all other morphological features at P > 0.001. Available K in medium also correlated significantly and positively with roots/plant, leaves/plant, and leaf area at P > 0.001, but positive and significant with number of roots, root fresh weight and root and shoot dry weight at P > 0.01. Soil pH, however, negatively and significantly correlated with roots and leaves/plant, and root and shoot dry weight at P > 0.05, and with root fresh weight at P > 0.01. 

 Only few anatomical features showed significant correlations with soil physico-chemical characteristics. In root anatomy, cortical cell area showed negative correlation with water holding capacity and available N, whereas metaxylem area with water holding capacity, and available N, P, and K. A positive and significant correlation of epidermis thickness and cortical region thickness was recorded with available P and K. Sclerification in endodermis and the vascular region showed significant and positive correlation with water holding capacity, and available N, P, and K in soil. In leaf anatomy, only metaxylem area, showed significant positive correlation with these soil parameters. 

Discussion

 Physical properties of the soil are considered main factors interrelated to plant’s performance in potting medium (Chen et al. 1988). Different commercial available potting media (i.e. peat, coir, coconut fibre, sawdust, jiffy etc.) can hold additional water (Goh and Haynes 1977) this is also confirmed in present study. In present study it was found that media in which farmyard manure were added had high pH this is due to fact that farmyard manure are basic in nature and it increased the pH because organic compound present in it (Fitzpatrick et al. 1998). Differences in nitrogen contents in different media compositions could be due to difference in OM contents (Ouyang et al. 1984; Younis et al. 2010). Goh and Haynes (1977) reported higher phosphorus in peat + sand; peat, sand + sawdust + peat, sand + soil than solitary soil.

 Martinez et al. (1982) reported increased plant height of Dieffenbachia plants growing in peat + bark as a medium, but Logan et al. (1984) reported suppressing effects on growth by this medium. DeBoddt and Verdonock (1971) obtained better root development by using peat perlite as a medium. Shah et al. (2006) recorded maximum root length in treatment having peat, sand and farm yard manure as a medium. In present study, more vegetative growth was observed in media treatments which have high nitrogen percentage (Table 1) which shows accordance with findings of other researchers on different plants like rose (Younis et al. 2013), dahlia (Tariq et al. 2012), gerbera (Younis et al. 2011). Deboddt and Verdonock (1971) reported more number of leaves in Monstera deleciosa in media composed of sand and peat. However, Fascella and Zizzo (2005) reported maximum number of leaves in new passion-flower when grown in nitrogen-rich perlite and coconut mixed media. Martinez et al. (1982) reported increased leaf area of Dieffenbachia plants when the peat + bark were used as a medium. Shah et al. (2006) also reported the maximum fresh root weight by using a mixture of sand, peat, and farm yard manure as a medium. Khan et al. (2002) reported better growth quality of Gladiolus by using peat, sand and silt in a medium. 

 Root epidermis is directly exposed to the external environments, and can play a key role in water and solute translocation (Van der Vliet et al. 2007, Younis et al. 2013). Shah et al. (2006) found increased root dry weight in Ficus binnendijkii by using a mixture of sand, peat, farm yard manure in a medium. Worrall (1981) reported increased root dry weight in Impatiens walleriana by using same medium. However, plants growing in GS, S + CC, S + FM, and S + LC did not show prominent sclerification, which is generally related to drought tolerance (Fatima et al. 2012) and also provide mechanical strength to root tissue (Nawaz et al. 2012). Pith, along with cortical parenchyma is the major storing tissue in the root, and larger cell with large vacuoles may have better capacity of storing water and nutrients than the smaller ones (Ola et al. 2012). Thick epidermis along with cuticle is related to drought tolerance, and therefore, may be critical when water holding capacity of a medium is low. Leaf epidermal layer is a protection to environmental hazards, and therefore, its size and nature can play a critical role in tolerating a variety of stresses (Bosabalidis and Kofidis 2002). Cortical parenchyma is the major storing tissue in plants, and especially in water limiting environments, its role is very critical (Hameed et al. 2012). Large vascular bundles are generally related to water and nutrient conduction (Tao et al. 2009). Phloem area is directly related to conductivity of the prepared food material in plants (Oruade-Dimaro et al. 2010), and larger area of this tissue is certainly more efficient. 

 In relation to morphological parameters of Dracaena reflexa ‘Variegata’, medium prepared from a mixture of sand, mushroom compost, coconut coir, and peat proved to be the best, which promotes root and shoot growth, leaf area, fresh and dry weights of root and shoot, and overall quality of the plant. The second best was a mixture of sand and peat, which improved all other parameters except plant height, whereas the third best was a mixture of sand, mushroom compost, farmyard manure, and peat. Media containing garden soil alone or a mixture of sand and leaf compost produced the lowest quality of plants with considerable reduction in most of the growth parameters. 

 Anatomical parameters showed a weak relation to media composition of other morphological features. The best media (S + MC + CC + P) showed thick epidermis, larger pith cells, but thin endodermis, and smaller metaxylem vessels in their roots. As moisture availability was sufficient enough in this media, the development of water storing tissue may not contribute significantly. However, the epidermis can play a decisive role in protecting roots from external environmental hazards.

Acknowledgment

 This research was supported by Kyungpook National University research fund, 2013.

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