Das MC; Nath AJ; Singnar P; Das AK

Research Article

J Plant Chem and Ecophysiol. 2016; 1(1): 1003.

Effect of Fruit Mass on Germination and Seedling Characteristics of a Tropical Climbing Bamboo Melocalamus compactiflorus (Kurz) Benth

Das MC, Nath AJ*, Singnar P and Das AK

Department of Ecology and Environmental Science, Assam University Silchar, India

*Corresponding author: Arun Jyoti Nath, Department of Ecology and Environmental Science, Assam University, Silchar, Assam, India

Received: February 02, 2016; Accepted: March 22, 2016; Published: March 24, 2016

Abstract

Fruit mass plays an important role in germination and establishment of bamboo species in forest ecosystems. Melocalamus compactiflorus (Kurz) Benth, a tropical climbing bamboo naturally distributed in forests of North East India (NEI) flowered gregariously, set seed and died in 2011-2012. The reported flowering cycle of the species is ~45 yrs. Therefore, present study is an opportunity to explore: (i) effect of fruit mass on germination and growth of seedlings, and (ii) effect of fruit age on viability and germination. Study revealed negative correlation between fruit mass and germination time (r=0.65; p<0.05; N=300). Statistically positive significant effect of fruit mass on seedling survival and seedling attributes (mean seedling height, diameter of seedling, total leaf number and leaf area) was observed. Increase in fruit age decreased the moisture content, germination rate (%), Mean Germination Time (MGT) and Seed Vigour Index (SVI) of the seedlings. Present study suggests heavy weight fruits promote germination rate and therefore set-in-motion for successful establishment of regenerating stands.

Keywords: Climbing bamboo; Germination; Mean germination time; Seed vigour index; Seed mass; Regeneration

Introduction

Seed mass within a species is considered to be a remarkably perpetual characteristic [1,2]. However, studies indicate variation in seed size and weight within the species [3-5]. Such seed weight variation may affect seedling characteristics and, thus, recruitment process [2,6]. Large sized seeds germinate faster and in higher numbers than smaller seeds [7]. However, a reversed situation was also reported where small seeds germinated more rapidly than large seeds, may be, to gain a competitive advantage [8]. It seems that relationship between seed mass and germination rate is restricted to species level and is not governed by any rule. Empirical studies have shown that seed size can affect seedling survival, growth and establishment [9-12]. Over the past years, many investigators studied relationships between seed mass, germination rate and seedling vigor for different herb, shrub and tree species but it remained unexplored for any bamboo species. Generally bamboo produces one-seeded fruits with thin pericarp adnate to the seed coat, known as caryopsis [13] and such fruit or caryopsis differ morphologically and anatomically from any woody tree seeds [14]. Therefore, it is important to examine fruit behavior of bamboo species in relation to germination rate. In the present investigation, we took the advantage of gregarious flowering and mast seeding of a tropical climbing bamboo to investigate relationship of fruit mass and germination of Melocalamus compactiflorus (Kurz) Benth.

Characteristics of different generations sprout (ramet) of a seedling vary within the regeneration phase. Their survival period and growth completion period plays a key role in establishment of regenerated seedlings [4,15-17]. Unusual flowering behaviour, long and irregular inter seeding period raises concern about bamboo propagation through seeds [14,18-21]. Moreover, flowering and seed production in bamboo is rare and the flowering cycle ranges from 3-120 years [14,18,21,22]. Although bamboo produces abundant seeds through mass flowering [18,22], but, due to the unusual flowering habit planting stocks faces the risk of synchronous flowering [17- 20]. Propagation through seed is very important because it maintains genetic diversity within population [23] and the scientific knowledge of the morphology, germination and longevity of bamboo fruits promotes their better utilization at the time of availability [24,25]. Melocalamus compactiflorus (Kurz) Benth, flowered gregariously in 2011-2012, after 45 years of long vegetative growth [26], and due to long seed setting period, few, if any, attempts have been made to explore the fruits and seedling characteristics. Therefore, present paper specifically aims to describe (i) effect of fruit weight on germination and growth of seedlings, and (ii) effect of fruit age on viability and germination.

Materials and Methods

Study species

Melocalamus compactiflorus (Kurz) Benth locally ‘loti bamboo’ is a semelparous tropical climbing bamboo, sparsely distributed in forest tracts of Barak Valley, Assam. The species naturally grows on other trees in liana like fashion and prefers fringes of perennial streams in semievergreen and evergreen forests of heavy rainfall areas [13,26]. Culms are climbing in nature, base portion of culm is solid, grayish-green, culms and branches bending and scattering over the host tall trees, 15-45 m tall, and 2-4.5 cm in diameter. Branching starts from 5^th to 6^th nodes of the main Culm. The seeds are caryopsis with fleshy pericarp, semicircular 1.5-3.5 cm long, 1.5-3.0 cm diameter, weight of the fresh fruits varies from 1.5-15.0 g.

Study sites

The study was carried out in Inner-line Reserve Forest (IRF) (92°44’075’’ E, 24°36’161’’ N) of Cachar district, Assam, North East India. This tropical climbing bamboo flowered gregariously during 2011-12 in the entire range of IRF [26]. The climate of Cachar district is sub-tropical and humid, with a mean annual rainfall 2,500 mm, the annual average temperature varies from 11.5 °C to 34 °C, mean annual relative humidity of this study site varies from 60 to 84% (Figure 1). The vegetation of the study site is dominated by Palaquium polyanthum, Cynometra polyandra, Sapium baccatum and Ficus sp. etc.

Figure 1: Climatic conditions of study site.

    
    
    Figure 1:  Climatic conditions of study site.

Fruit collection

Mature fruits were collected during the month of March-April 2013 by manually shaking the fruiting culms after spreading a canvas sheet on the ground. Care was taken to collect only freshly fallen fruits. The fruits were packed in jute bags and transported to the laboratory and thoroughly cleaned and stored in jute bags until the start of the experiments.

Selection of fruits

Viable fruits were selected for germination test. For viability test, fruits were soaked in water. Those immersed in water were considered as viable and floated ones as non-viable or affected fruits. Depending on the fruit mass they were categorized into three categories: light (< 5 g), intermediate (5.1-10 g) and heavy (> 10.1 g).

Germination experiment

The germination test was carried out in petriplates on moistened filter paper. The test was carried out taking 100 fruits in each weight category. The number of fruits germinated was counted and recorded daily for one month. When plumule was 3 cm tall, germinated fruits were transplanted in polybags containing forest floor soil, cow dung and sand in the ratio 1:1:1.

Height growth and growth rate of seedlings

For this study, polybags containing seedling were transferred in a well prepared nursery. The seedlings of each weight category were marked with aluminum foil. The height and diameter of seedlings were measured using metallic measuring tape and digital slide calipers. Diameter was noted at the 3^rd internodes of the seedling. Total number of leaves per seedling, leaf length and leaf width were also recorded for each seedling. For the maintenance of the moisture of soil and air, water was sprinkled twice daily for the first two months, and once daily for the later period of study.

Growth behavior of different generation sprouts

For this study, the marked sprouts were observed for 24 months. Height increment, diameter of sprouts, regenerated new sprouts in each seedling, development of side branch-lets and growth stunted time were recorded daily.

Fruit longevity

To study the fruit longevity, a total of 720 fruit were sorted out from the collected fruit bank. Of the total fruits (720), (i) 360 were kept under open places (in petriplates), and, (ii) 360 were kept in jute bags filled with sand. At monthly intervals 30 fruits in (i) and (ii) were taken out to determine their moisture content. In addition to that, another 30 fruits from each experiment were studied at monthly interval for their fruit viability and germination time. Mean Germination Time (MGT) and Seed Vigour Index (SVI) were calculated [27].

Data analysis

Statistical analysis of the data was carried out using MS-Excel and SPSS. The normality test of different parameter was carried out using Kolmogorov-Smirnova test. Further, Pearson correlation test was carried out for normally distributed data and Spearman’s Correlation test for non-normal data. Kruskal-Walis [28] test was performed for the estimation of variance non-normal data distribution using SPSS.

Results

Germination and growth behaviour

Highest germination was observed with heavy fruits (95%) followed by intermediate and light fruits (81% and 72%, respectively). Heavy weight fruits germinated faster than intermediate and light fruits (Table 1, Figure 2). A negative correlation between germination time and fruit weight was observed (r=0.655; p<0.05; N=300). Fruit germination started after two days of keeping fruits in petriplates within the moistened filter paper. No fruit germinated after 7 days in all categories of fruits. Seedling height was significantly influenced by fruit weight (H=258.830; p<0.001). Heavy weight fruits showed maximum height (85.44 cm) over intermediate (60.00 cm) and light weight (52.90 cm) (Table 2). Growth rate of the regenerated seedlings varied among different fruit weight categories. Growth rate was high during the first few weeks after transplanting (Figure 3). The fruit weight had positive influence on growth rate but was statistically not significant (H = 0.362; p= 0.834).

Table 1: Summary table of germination of fruits with respect to different weight categories.




  
    Weight classes (g) 
    N 
    % of germinated fruits 
    % of non- germinated fruits 
  
  
    Light 
    300
    72
    28
  
  
    Intermediate 
    300
    81
    19
  
  
    Heavy 
    300
    95
    05



Table 1:  Summary table of germination of fruits with respect to different weight
categories.

Table 2: Descriptive statistics of seedling height of different fruit weight categories.




  
    Weight classes (g) 
    Minimum Seedling height (cm) 
    Maximum seedling height (cm) 
    Mean seedling height (cm) 
  
  
    Light 
    0.26 (n=100)
    52.90
    39.36
  
  
    Intermediate 
    0.39 (n=100)
    60.00
    46.89
  
  
    Heavy 
    0.23 (n=100)
    85.44
    62.13



Table 2:  Descriptive statistics of seedling height of different fruit weight categories.

Figure 2: Cumulative germination curve of different weight seeds.

    
    
    Figure 2:  Cumulative germination curve of different weight seeds.

Figure 3: Growth rate of different fruit mass seedling categories.

    
    
    Figure 3:  Growth rate of different fruit mass seedling categories.

It took 55 to 63 days to complete growth of first generation sprouts. Average height and diameter of the first generation sprouts were 57 cm and 0.25 cm, respectively (Figure 4, Table 3). After the completion of growth of first generation seedling, in the next growing season second generation seedling started to develop. Within 56 days, second generation sprouts completed their growth (Figure 4). Third and fourth generation sprout developed in the same year as of second generation sprout. Morphological attributes (side branch-lets) were well developed in third and fourth generation seedlings.

Table 3: Seedling attributes of different seed weight categories (Mean±SE).




  
    Weight classes(g) 
    Height of seedling(cm) 
    Diameter of seedling(cm) 
    Total no. of leaves seedling^-1 
    Leaf size (cm²leaf^-1) 
    Total no. of culms 
  
  
    Heavy 
    85.44^a ±2.84
    0.589^a±0.177
    10^a±0.29
    81.94^a±2.11
    5±0.13
  
  
    Intermediate 
    60.00^b ±4.50
    0.518^b ±0.18
    8^b±0.13
    62.66^b±2.22
    5±0.11
  
  
    Light 
    52.90^c ±2.66
    0.406^c ±0.11
    7^c±0.26
    58.22^c±2.50
    4±0.11
  
  
    ^*Different letters are    significantly different at p < 0.05 as measured by LSD between seed    age.



Table 3:  Seedling attributes of different seed weight categories (Mean±SE).

Figure 4: Growth behavior of different sprouts. All generation sprouts completes their growth within 56-70 days after germination. Height growth in M. compactiflorus is independent of fruit mass.

    
    
    Figure 4:  Growth behavior of different sprouts. All generation sprouts
completes their growth within 56-70 days after germination. Height growth in
M. compactiflorus is independent of fruit mass.

Effect of fruit age on moisture content (%), germination (%), Mean Germination Time (MGT) and Seed Vigour Index (SVI)

Increase in fruit age decreased the moisture content of fruits (Table 4). The fruit stored in sand contained high moisture content (10.25%) than those stored in jar in room temperature (5.12%) after six months of fruit storage. The fruits stored at room temperature lost their viability within five months in comparison to six months in sand (Table 5). The MGT increased with fruit age but not statistically significant. The SVI was observed more in fruits stored in sand than those in sealed jar (Table 5).

Table 4: Seedling attributes of the different generations of seedling sprouts (Mean±SE).




  
    Generation 
      of seedling 
    Height of seedling(cm) 
    Diameter of seedling (cm) 
    Total no of leaves seedling^-1 
    Leaf size(cm²leaf^-1) 
  
  
    1 
    56.58±1.26
    0.25±0.02
    4±0.35
    19.44±1.20
  
  
    2 
    80.9±1.79
    0.32±0.16
    7±0.18
    36.3±1.83
  
  
    3 
    110.8±0.95
    0.406±0.12
    9±1.20
    54.6±2.46
  
  
    4 
    170±0.95
    0.589±0.17
    13±1.2
    102.4±2.80
  
  
    5 
    220.8±2.31
    0.69±0.27
    16±2.3
    143.36±2.40



Table 4:  Seedling attributes of the different generations of seedling sprouts (Mean±SE).

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Citation: Das MC, Nath AJ, Singnar P and Das AK. Effect of Fruit Mass on Germination and Seedling Characteristics of a Tropical Climbing Bamboo Melocalamus compactiflorus (Kurz) Benth. J Plant Chem and Ecophysiol. 2016; 1(1): 1003. ISSN: 2572-4371

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Age of fruit (months)	Moisture Content (%)		Germination (%)		MGT(days)		SVI
Age of fruit (months)	Fruit stored at room temp.	Fruit stored in sand	Fruit stored at room temperature	Fruit stored in sand	Fruit stored at room temp.	Fruit stored in sand	Fruit stored at room temp.	Fruit stored in sand
1	68.52^a(±1.80)	78.72^a (±1.80)	93.33^a	100^a	4.32(±0.24)	4.25(±0.25)	18.51^a	22.08^a
2	57.81^b(±2.31)	58.12^b(±2.41)	53.3^b	73^b	6.97(±0.45)	7.29(±0.35)	8.77^b	15.40^b
3	50.25^c(±1.67)	54.94^c(±2.75)	40^c	60^c	8.33(±0.22)	7.90(±0.23)	5.04^c	8.22^c
4	44.68^d(±0.91)	47.69^d (±1.78)	30^d	46.67^d	10.54(±0.31)	10.35(±0.32)	2.90^d	3.09^d
5	16.72^e(±1.73)	28.02^e (±2.43)	0.0^e	16.67^e	0.0	10.54(±0.31)	0.0^e	1.91^e
6	5.12^f(±1.83)	10.25^f (±2.80)	0.0	0.0	0.0	0.0	0.0	0.0
^*In a column means followed by different letters are significantly different at p < 0.05, as measured by LSD.