Effects of salinity on physiological and growth parameters of Melia composita Willd. at establishment stage
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Date
2015
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CCSHAU
Abstract
The objectives of present investigation were to assess the extent of salt tolerance in Melia composita
seedlings at establishment stage and also to study the effect of salinity levels (control, 4, 8, 12, 16, 20, 24, 28, 32, 36
and 40 dSm-1) on various physiological and growth parameters. In this experiment, seeds from selected plus tree were
grown in pots in screen house containing sand and soil in 2:1 proportion. Six seeds were sown in each pot; however,
after germination 3 seedlings were maintained in each pot. All the pots were irrigated with normal water till 90 days of
their growth and after three months the seedlings were subjected to salinity stress for 25 days by irrigating with saline
water till the point of tolerance to salinity. Required saline concentration were prepared by adding calculated amounts
of chloride and sulphate salts of Na, Ca, and Mg as solutions on equivalent weight basis.
It was observed that salinity stress caused decreases in stem radial diameter and shoot length compared
to control plants. These decreases were, however, less in radial growth in 4 dSm-1 adapted seedlings compared to
the increased salinity stress. A significant increment in basal diameter was observed in control seedlings (57.9%)
compared to 8 dSm-1 salinity level. Similarly, shoot length also decreased significantly in response to salt stress. It
was found that the root length decreased significantly at 12 dSm-1 compared to control, however, root build up was
not negatively affected at 4 and 8 dSm-1 levels. Significant increase in number of leaves was observed in nonstressed
seedlings; however, salinity stress caused significant reduction in number of leaves at 4, 8 and 12 dSm-1
(13.9%, 19.4% and 39.7%, respectively) when compared to control plants. Similar significant reductions in plant
part biomass were also found at 8 and 12 dSm-1 salinity level compared to control. Total chlorophyll contents in
leaves declined in response to increasing salt stress; but, an increase in chlorophyll content was observed at
4 dSm-1 (16.18 mg/g) compared to control (15.80 mg/g), which was 2.40% more than the mean value of control.
Beyond 4 dSm-1, total chlorophyll content in leaves reduced significantly compared to control. In contrast,
carotenoid contents in leaves increased significantly in response to increasing salinity levels. Proline accumulation
in leaves increased significantly in 4 and 8 dSm-1 adapted seedlings in response to salinity stress compared to
control, and it was accumulated 3 times more in 8 dSm-1 adapted seedlings compared to control. At 4 dSm-1
adapted seedlings, leaves sugar levels were 11.06% higher compared to control seedlings and these were still
significantly higher and on the increasing trend (22.74% more) in 8 dSm-1 adapted plants. Salt stress caused
significant decrease (6.25%) in moisture content in leaves of 8 dSm-1 adapted seedlings. It was, however, observed
in this experiment that the greater the cell damage, the greater was the leakage which resulted in higher
conductivity. Leakage of electrolytes were 67.8 and 104.0% more in 4 and 8 dSm-1 adapted seedlings, respectively
compared to control. All the physiological and growth parameters were determined only up to 12 dSm-1 level.
After 8 dSm-1 plants could not survive due to ions toxicity and mortality occurred.
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