Saline stress is one of the main factors limiting legume productivity
(Lluch et al., 2007). Seed germination is usually the most critical stage in seedling establishment, which determines successful crop production
(Almansourie et al., 2001; Bhattacharjee, 2008). In the present experiment, the data on mean germination percentage showed declining trend with increase in salinity levels (Table 1). The pelleting treatments significantly increased the germination percentage at all levels of salinity when compared with the control treatment. The highest germination percentage was observed in treatment with
Pongamia pinnata leaf powder pellets @ 200 g per kg (T
4) which recorded the maximum germination of 87.33 per cent at no saline condition, 85.00 per cent at EC
4, 84.66 per cent at EC
8, 80.33 per cent at EC
12 and 74.33 per cent at EC
16 levels (Table 1). The next best treatment was
Pongamia pinnata leaf powder pellets @ 150 g per kg (T
3). The mean data on speed of germination suggested that salinity has drastically delayed germination. The pelleting treatments significantly increased the speed of germination both under normal and induced saline condition. The highest speed of germination was recorded in
Pongamia pinnata leaf powder pellets @ 200 g per kg (T
4), which recorded speed of germination of 9.50 at control condition, 9.30 at EC
4, 9.10 at EC
8, 8.80 at EC
12 and 8.50 at EC
16 levels, followed by 150 g per kg (T
3) in which the maximum speed of germination was recorded at control (9.30) and the minimum at EC
16 levels (7.40).
The improvement in field emergence could be attributed to activation of cells, resulting in the enhancement of mitochondrial activity leading to the formation of more high energy compounds and vital biomolecules, which are made available during the early phase of germination
(Ananthi et al., 2015). Salinity has delayed germination which has already been reported by
Ayers and Westcot (1985) and
Mensah and Ihenyen (2009). The variation in seed germination at higher levels of NaCl indicated that NaCl has direct harmful effects on common bean seed germination (
Alihan Cokkizgin, 2012). This increase in seed vigour was also due to the early availability of high energy compounds and vital bio molecules to the growing seedlings. The
Prosopis juliflora leaf powder contains saponin like substance which acts as a precursor of GA
3 (
Manikandan and Srimathi, 2014). During pelleting, the leaf powder might have helped to regulate the soil moisture availability and thus enhanced seedling quality characters of the pelleted seeds.
It has been observed that increased saline concentration caused harmful effects on seedling growth in terms of root length, shoot length, and dry matter production. However, pelleting treatments increased these parameters at all levels of salinity when compared with the control treatment (Fig 1). In general, the highest seedling growth parameters
viz., root length, shoot length and dry matter production were recorded at control (14.46 cm, 17.33 cm and 0.56 g) followed by salinity levels from low (EC
4) to high (EC
16) (13.78 cm, 13.42 cm, 12.98 cm and 12.58 cm of root length at EC
4, EC8, EC
12 and EC
16; 16.39 cm, 15.85 cm, 15.19 cm and 14.65 cm of shoot length at EC
4, EC
8, EC
12 and EC
16; 0.54 g, 0.53 g, 0.52 g, and 0.50 g of dry matter production at EC
4, EC
8, EC
12 and EC
16 conditions respectively) in pelleting treatment with
Pongamia pinnata leaf powder @ 200g per kg. In control and low levels (EC
4 and EC
8) of salinity, the next best treatment was
Pongamia pinnata leaf powder pelleting @ 150g per kg. However, in high levels of salinity, pelleting with
Albizia amara leaf powder @ 200g per kg performed as the next best treatment. Similar results were observed by
Khajeh-Hosseini et al., (2003) in soybean seeds and by
Pujol et al., (2000) in four halophytes from south eastern Spain.
The increase in root length, shoot length and seedling length may be due to the cell wall extension and increased metabolic activities as reported by
Afzal et al., (2002) in maize seeds. Increase in dry matter production with seed pelleting was also reported by
Tamilmani (2012) in blackgram and
Prakash et al., (2013) in rice. The increase in dry weight was claimed to be due to enhanced lipid utilization and enzyme activity due to the bioactive substances like auxin present in
Prosopis juliflora leaf extract (
Kathirvel and Kumudha, 2011). Similar observations of increased growth parameters with 1%
Prosopis juliflora leaf extract treatment was reported in black gram by Sathiya
Narayanan et al., (2016).
The bionutrients available in the pelleted seeds might have improved seedling growth resulting in higher growth parameters
(Prakash et al., 2013). The physiologically active substances present in the botanical leaf powders might have stimulated the germination and related processes resulting in more absorption of water due to elasticity of cell wall and development and increased vigour index (
Sathish and Bhaskaran, 2013). The
Pongmia pinnata leaves contain various alkaloids like pinnalin, pongamol, saponin, β-sitosterol and tannins (
Savita Sangwan et al., 2010). Presence of these substances in
Prosopis juliflora and
Pongamia pinnata leaf powders would have triggered the germination and seedling establishment processes thereby increase the uptake of nutrients resulting in enhanced growth and development. The influence of seed pelleting in rice
(Prakash et al., 2013) and bhendi
(Prakash et al., 2014) has already been reported.
Increased salinity concentration decreased the vigour index of cluster bean seedlings. In general, the highest vigour index I (2692.65, 2590.80, 2531.76, 2389.60, and 2178.56 at control, EC
4, EC
8, EC
12 and EC
16 conditions respectively) and vigour index II (48.72, 45.90, 44.52, 40.80 and 36.26 at control, EC
4, EC
8, EC
12 and EC
16 conditions respectively) were recorded in pelleting treatment with
Pongamia pinnata leaf powder @ 200g per kg (Table 2).
Al-Mutawa (2003) reported that increased salinity leads to decreased root length in chickpea. During soaking, seeds become physiologically advanced by carrying out some of the initial steps of that resulted in improved germination, seedling length, dry matter production and vigour index (
Natesan, 2006). The finding of
Ramesh Kumar and Muthukrishna (2015) in okra and chilli seeds and
Georgin Ophelia (2017) in black gram also corroborates with the results of present study. Increased seedling growth observed due to
Pongamia pinnata leaf powder is in concomitant with the reports of Harish Babu
et al., (2005) who observed increased shoot length, seedling dry weight and vigour index. The effect of
Prosopis juliflora and
Albizia amara leaf powder treatments in enhancing vigour of seedlings is in line with the observations of
Ananthi et al., (2015) and Sathish
Kumar et al., (2014) respectively.
To conclude, seed pelleting with
Pongamia pinnata leaf powder @ 200g per kg can be recommended for cultivation of cluster bean under saline conditions to get higher yield.