Within the Tamariacacea family, there are 4 genera and 289 species (The Plant List, 2010). This family thrives in temperate conditions and can be found distributed as such in Europe, Asia and Africa within their maritime deserts and sandy tracts. This family is not abundant on Indian subcontinent where its representation is 20% of all species spread between Srilanka, India, Pakistan, Bangladesh, Bhutan and Myanmar (Kundu, 2009). Having thought to have its origins in the Central Sahara, it then spread throughout North Africa, Egypt and the Middle East spreading to India, Afghanistan and Pakistan. The spread also covered the areas of Eriteria, Kenya and Ethiopia (CABI, 2015). Tamariacacea is a small family of about 4 genera and 289 species (The Plant List, 2010) temperate in distribution, usually found in sandy tracts and maritime deserts of Asia, Africa and Europe. On the Indian subcontinent (comprising Bangladesh, Bhutan, Myanmar, Nepal, Pakistan, Sri Lanka and India), the family Tamaricaceae is poorly represented (20% of all species) (Kundu, 2009). Qaisar (1982) stated that in Pakistan it is represented by 4 genera and 35 species. The native range of T. aphylla extends over the Middle East, North, East and Central Africa, and parts of West and South Asia. The species is thought to have originated in the Central Sahara, from where it spread to Pakistan, India, Afghanistan, the Middle East, Egypt and North Africa, as well as to Eritrea, Somalia, Kenya and Ethiopia (CABI, 2015; Orwa et al., 2009).
T. aphylla is evergreen, moderate sized and fast growing tree of upto 18 m height with an erect tapering trunk and smooth branches. Department of Agriculture and Fisheries (2013) concluded that it is heat, salt, draught and frost tolerant. Mature trees of T. aphylla have dark grey to black and rough stem of up to 1 m in diameter but immature trees have light grey trunks. Department of Land Resources Management (2014) concluded that even because of pendulous needles and branches, it is not a true pine or conifer. Silvery grey appearance on tree foliage of whitish coating is because of salt secreting glands from the needles. Small, white and pink flowers occur in dense racemes. Biophysical limits of T. aphylla are 0 to 1200 m above sea level, mean annual rainfall is 250 to 500 mm and mean annual temperature is 10 to 50°C. Tamarix aphylla grows naturally in canals, riverbanks, coastal plains, salt marshes, salty deserts and sand dunes. It can grow positively in saline soil and expand in occasional inundation areas than never flooded ones. It flourishes on loamy soils and can grow easily on stiff clays and sand. Nowadays, T. aphylla's wood can be used in different ways. Soft branches and leaves also provide a good quality of forage especially in dry time scale of the year. Its wood is flammable and can be used for firewood and charcoal (calorific value, 4835 kcal/kg) but catches fire slowly because of salt contents especially in small branches (Orwa et al., 2009). Its wood is used as fuel in United States and has been proposed for fence posts (Guler et al., 2007). T. aphylla have close-grain wood which is helpful in making carts, tool handles, ornaments, furniture, wheels, carpentry and fruit boxes (Orwa et al., 2009). On the other hand, it has been found to be a suitable raw material for making particle boards and can be used as biomass for sugar production (Sadegh et al., 2012; Hashemi, 2011).
There are different ways to propagate or multiply a plant. In Tamariacacea, there are 120 species but this study will focus on T. aphylla. A plant can be grown from their seeds or cutting off a portion of an established plant (Welch-Keesey and Lerner, 2009) and in the same way Tamarix species can naturally be reproducde from seeds and their broked stem fragments. The successful rate of vegetative propagation is quite higher especially when branches broken up by floodwater carry downstream (Crushes, 2008). A cutting is any detached plant part which, under favorable conditions, will produce a new plant identical to the parent plant (Hamilton and Midcap, 2003). A new plant grown form the cuttings of a parent plant which can grow faster and avoids all difficulties then growing from a seed. Vegetative propagation through cuttings or asexual reproduction is still very productive method so evergreen needled trees can also reproduce by parent plant cuttings (Welch-Keesey and Lerner, 2009). In open air, the viability of T. aphylla's recalcitrant seed is very low not more than a week, their germinative capacity keep reducing with the passage of time and therefore for better results immediate sowing is the only solution (Orwa et al., 2009). So, the yield of a tree produced from a cutting can be greater than a tree produced from seed. Boles produced by cuttings have better quality and less tapered (Hudson, 2009). Hybridization between superior species, as well as creating orchards of improved trees, has been examined in research. In order to realize genetic goals in tree species, several generations of tree breeding are required and each generation can last for 15 to 50 years depending on the species. Within the past few decades, genetic improvement of tree species has accelerated within the forest industry. Currently, the dilemma is how to speed up this process.
Asexual propagation (vegetative reproduction through cuttings) is one of the methods to solve this question. Until 1971, there were only three propagation programs introduced to this world (Ritchie, 1991), but now this process is successful as a nursery management tool (Hudson, 2009). Arrington (2015) stated that one of the many main advantages of asexual reproduction is the advantage of speed because it does not consider the gamete formation process and another is that the offspring are clones of the parents. The size of length of cuttings can differ according to different plant species (Edson, 1991). McCormack (2006) suggested that different cutting lengths can affect the prosperous rooting in Morus alba. So, it is very important to consider the age and size of planting material for initial survival and formation of seedlings (Haq, 1992) and establishment of cuttings and the early life stages of a plant are critical for the establishment of high seedling mortality. The root growth depends on node position, cutting length and leaf area factors and the success of rooting from cuttings depends on the factors like environmental, genotype and physiological state (Ahmed et al., 2011). So, it is vital to upgrade the use of local species by vegetative means (Weber and Stoney, 1986; Arriaga, 1994; Leakey et al., 1994), because propagation by seedlings took a very long time (Ahmed et al., 2011). Desired results from cuttings may affect if environmental conditions are not supplied properly (Hamilton and Micap, 2003). A cover can be used for the existence and initial formation of plants. Humid conditions are quite suitable for the rooting process of M. alba and umbrella of greenhouse with plastic cover (Ahmed et al., 2011). Trujillo (2002) also favored plastic cover for the success of cuttings in the nursery. So it is quite settled that polythene cover really affects the different parameters of a plant.
In 1823, Tamarix species were first introduced into the United States but now they are planted as windbreaks, ornamental and for stream bank stabilisation (Crushes, 2008). T. aphylla recognised as windbreaks, erosion control, sand dune problems and as an ornament. However, it is planted in the hot deserts of Iran to control sand dunes problems (Sadegh et al., 2012).
The experiment was carried out at experimental area of the Department of Forestry, University of Agriculture Faisalabad. Latitude 36 to 26° and Longitude 73 to 06°E.
Cutting preparation and planting
Three different sizes of branch cuttings (2", 4" and 6" long) of Farash (T. aphylla) were prepared from six-year-old healthy trees in the first week of August 2008. These cuttings were then planted and irrigated immediately in the polythene bags of 3" × 7" size which were filled with sandy loam soil. Half of these bags were placed in the open air, while the remaining half was placed under the low polytunnel. There were two experiments (open air block and under low polytunnel block) were organised in accordance with Randomized Complete Block Design (RCBD) with three replications each. The data on sprouting percentage and height of plant were recorded after 15, 30, 45 and 60 days but root length and root branches data was recorded right after 60 days. There were three treatments in each replica and three treatments were labeled as T1 for 2" long cuttings; T2 for 4" long cuttings and T3 for 6" long cuttings. There were 50 polythene bags in each treatment (T1, T2 and T3) which makes 150 in each replica of open air and under polytunnel, making a total of 900 bags for the whole experiment. The data were subjected to analysis of variance and comparison among the treatments by the Least Significant Difference Test at 5% probability level (Steel et al., 1997).
It is vital to find out the survival percentage of plants by the propagation of different size of stem cuttings in different environmental conditions. The maximum sprouting after 15 days was observed in T3 (77.55%) under polytunnel while in open air it was only 29.10% (Table 1). Overall, after 30 days, there was a negligible increase in the sprouting percentage, thus thirty days are adequate for assessing sprouting. The results of the present study showed that the cutting size and polythene cover influence the sprouting of tree cuttings at nursery stage. These findings are also in line with those of Mebrathu and Hanover (1990), Cobbina (1990), Haq (1992), Mitchell (1998), and Trujillo (2002).
The sprouting percentage in all treatments (T1, T2 and T3) was much higher under low polytunnel than in open air and after 60 days the most successful treatment was T3 (6" long cuttings) under low polytunnel with 86.85% (mean value 84.08%) sprouting and in open air it was only 63.23% (mean value 39.24%) (Figure 1). This significant figure clearly shows that the environmental conditions (polytunnel) do affect the sprouting percentage of T. aphylla. Rafay et al. (2015) revealed that the sprouting percentage was maximum with 6" cuttings under low polythene tunnel are maximum than others and in different mediums. So the results indicate that the low polytunnel is better for propagating T. aphylla plants from branch cuttings.
Height of plants (cm)
After 15 days, the height of plants exposed to the open air was less being 2.23 cm for T3 (6" long cuttings), 1.98 cm for T2 (4" long cuttings), and 1.52 cm for T1 (2" long cuttings). The plants were much taller in first 15 days when kept under low polytunnel being 3.21 cm for T3, 3.10 cm for T2 and 3.22 cm for T1 (Table 2). Overall, after 30 days, there was no difference in the height of plants in open air but under low polytunnel T3 have shown a significant height than other treatments. After 60 days, the results for plant height clearly shows (Figure 2) that under low polytunnel plants flourished and developed more vigorously with a mean difference of 3.54 cm than in open air (Table 2). Rafay et al. (2015) concluded that under low polythene tunnel the height of plants with 6" long cuttings achieved maximum height. These results also match the findings of Khan (2007).
Root length (cm)
The maximum root length of 20.14 cm was recorded in T1 (2" long cuttings) under polytunnel. Even the mean value of T1 in open air and under polytunnel is 19.63 cm which is higher than T2 and T3 mean values which are 18.67 and 18.24, respectively (Table 3). Length of roots were much better grown in the plants under low polytunnel (mean value 19.56 cm) than in the open air (mean value 18.14 cm) (Table 3). The results from T1 shows that root length can be developed in a better way, under polytunnel (Figure 3). The reason might be conservation of moisture and heat/temperature under the sheet cover, enhancing growth of plant roots. These results agree with the findings of Trujillo (2002).
The numbers of root branches were counted immediately after the completion of 60 days. The maximum number of root branches (21.23) were produced by T1 (2" long cuttings) in open air (Table 4). On the other hand, plants grown under polytunnel had slightly less root branches (18.75) than in open air. It is shown (Figure 4) that T1 (2"
long cuttings) in open air produced more roots than the the longer cuttings possibly because there was more space available to grow for them as compared to larger cuttings. Irfan (2011) concluded that 2" long cuttings produced more branches than others and in different mediums. Different researchers have previously observed that shorter cuttings lead to the development of more and better roots (Foster et al., 2000). It shows again the success rate of T1 with the number of root branches (mean value 19.99) is higher than other treatments (T2 and T3) is as similar to the results of measurement of roots length.
Although seedlings still costs less in most regions of the world, propagation through cuttings could be the best alternative to it to prepare more vigorous plants and more flowering in some cases in less period of time. The overall growth of plant cuttings under polytunnel was better as compared to the open air. The reason that under polytunnel, moisture was conserved and proper temperature for plant growth was maintained which resulted in the best results of sprouting percentage, plant height and root growth except the number of root branches. The numbers of root branches were higher in the open air than under low polytunnel which can be the result of small space available. All the growth parameter indicates that the performance of T3 treatment (6" long cuttings) is better than all other sizes of cuttings. So, keeping in view the conclusion, planting of 6" long cuttings of T. aphylla under low polytunnel is recommended for nursery raising.
The authors have not declared any conflict of interests.