The plants grown under salt stress condition were unable to absorb adequate water for its metabolic processes or maintain turgidity due to low osmotic potential (Shrivastava et al., 2015).
Salinity stress condition increases cations uptake such as Mg, Na, Ca and causes different kinds of nutritional imbalances finally leads to different ranges of toxicity. Among the cations, the most important one is NaCl toxicity, plants absorb more amount of Na+, which thus decreases the K uptake by plants (Ahmad and Prasad, 2012)
. The greengram genotypes grown under different salinity conditions affect its biochemical mechanism and leads to reduction in growth (Shanthi et al., 2011).
The two way ANOVA (Table 1) results clearly revealed that the main effects of salinity, genotypes and its interaction were highly significant in all parameters studied.
Table 1: Analysis of variance of different characters and various salt concentrations in greengram genotypes.
Hence the greengram genotypes taken for this study were varied in their response to different levels of salinity in germination and other characters in its seedling stage. The coefficient of variation varied among different characters and the maximum was recorded by the plumule radicle length ratio (15.39) and the minimum was recorded by dry matter weight (2.06). Similar result was also reported in blackgram (Shanthi et al., 2021a).
This was also confirmed by the critical difference (CD) for all characters taken for this experiment were compared for different factorial plots and subplots with their interactions.
The reduction in germination percentage was noticed for increasing salinity levels invariably in all the genotypes (Table 2).
Table 2: Mean germination percentage of greengram genotypes at different levels of salt concentration.
The genotypic difference was observed within and among the salinity levels. In overall performance, while compared with control (0.0 EC level), the reduction in germination percentage was very less at 4.0 EC level and very high at 16.0 EC level. Similar results were observed in greengram (Prakash, 2017)
and Shanthi et al., (2021a)
in blackgram. Variability in salinity tolerance among rice varieties was reported by (Shanthi et al., 2011)
and variation in germination has also been reported by Hakim et al., (2010).
Plumule length is the most important seedling character which affected due to salinity. Kumar et al., (2021)
reported that the salinity
is a major abiotic stress
that significantly affects
the plant growth
by causing osmotic stress
and inducing ionic and nutrient imbalance. The first visible symptom due to salinity is retarded growth (Shanthi et al., 2021b)
prolonged salinity the plumule length was reduced. The maximum plumule length after 8 days of germination was recorded by the genotype IPMD 14-10 (18.9 cm) (Table 3) and it was reduced to half in most of the genotypes studied under 8.0 EC level and the length was reduced high at 16.0 EC level.
Table 3: Mean plumule length of greengram genotypes at different levels of salt concentration.
This character can be considered as one of the important criteria for identification of salinity tolerant genotype(s). These results were in accordance with the findings of Prakash (2017)
The radicle length is another important parameter for salinity screening in seedling stage. Beyond the 4.0 EC level the gradual reduction in radicle length was observed and under 12.0 EC level almost in all the genotypes the radicle length was reduced to half as compare to control (0.0 EC) (Table 4).
Table 4: Mean radicle length of greengram genotypes at different levels of salt concentration.
Under 16.0 EC salinity condition all the genotypes recorded below 2.75 cm of radical length. These results indicated that the plumule length was more under control condition and reduced under stress conditions; whereas the radicle length was slightly increased up to 8.0 EC level and at 12.0 and 16.0 EC level both plumule and radicle lengths were reduced. The plumule length was severely affected by salinity and the radicle length was increased by slight increase in salt concentration to increase the water absorption rate and later at high salinity level (12.0 and 16.0 EC level) the radicle growth was also affected. The results were in accordance with Hanumantha Rao et al., (2016).
The average dry matter weight of single seedling under control is less than the seedling under salinity stress condition. The salinity level the dry matter weight also increased gradually and under higher saline concentration of 16.0 EC (Table 5).
Table 5: Mean dry weight of greengram genotypes at different levels of salt concentration.
Due to high level of salinity the sodium salt absorption by the plant may be increased that leads to accumulation in plants. Similar findings were also confirmed in blackgram by Shanthi et al., (2021b)
and Priyadharshini et al., (2019).
Salt tolerance index and salt injury index were used to determine the degree of tolerance for different genotypes towards salinity. Salt tolerant index for plumule length, radicle length and dry matter weight were calculated. The salt tolerance index was reduced by increasing salt concentration for both plumule and radicle length and salt injury index was increased vice a versa. This results clearly showed that the increasing salt concentration affect the plant height. While comparing root length the damage due to salinity was comparatively low in root compare to shoot. Similar result was recorded by Shanthi et al., (2021a).
Salinity stress significantly reduces the net photosynthetic rates, due to salt exclusion mechanism the energy losses was increased, nutrient mobilization largely decreased, cell division and cell elongation also reduced all this activity finally reduced the plant growth (Seeman and Sharkey, 1986)
Simple linear correlation
The linear correlation analysis was carried out for germination percentage, plumule length, radicle length, plumule radicle length percentage and dry matter weight under different EC level. The significant and positive correlation was recorded for germination percentage with plumule length at 4.0 EC level and 8.0 EC level and radicle length of control and 4.0 EC level. These results clarify that the lower level of salinity (up to 4.0 EC level) the germination percentage, plumule length and radicle length were not affected more. W-hereas beyond 4.0 EC level the germination percentage, radicle and plumule length were drastically affected (Table 6).
Table 6: Simple correlation analysis for the growth characters at different salinity level for the greengram genotypes.
Similar results were reported by Shanthi et al., (2021a).
Hence the radicle and plumule length can be taken as criteria for selection to identify the salt tolerant genotypes. Whereas the dry matter weight is concerned it has recorded negative and significant correlation with plumule length it clearly showed that the increasing salinity concentration reduced the plumule length and reduces the dry matter weight.