Introductory Crop Physiology (1+1)

Classification of plants depending on the tolerance towards the salt concentration

Classification of plants depending on the tolerance towards the salt concentration

1. Facultative halophytes
2. Obligate halophytes

1. Facultative halophytes

• These plants are particularly interesting, several such species grown best where salt levels in the soil are high as in desert or in soils saturated with brackish (Na) waters as in seas coasts or close to shores, where the salt content may be saturated at levels as high as 27 per cent by weight. They also grow in non-salty soils.
• The following genera include good examples: iodine bush, pickle weed, sea lavender, etc. these also grow in somewhat less salty soils.

2. Obligate halophytes:

• Barbour et al., (1980) reviewed the literature that suggest that there are no obligate halophytes. Plant that cannot grow unless the soil contain salt.
• So far all halophytes studied have been found growing naturally in non-salty soil and will grow well where planted in non-salty soils. Normally they are not abundant in non-salty soil because they cannot compete with the glycophyltes that normally grow there.
• Members of genus Halobacterium (prokaryotes) accumulates large amount of salts into their cells and cannot survive except in salty environment.
• Some halophytes are referred as salt accumulator. In these species the osmotic potential continues to become more negative throughout the growing season as slat is absorbed.
• Water moves into the plant osmotically and not simply in bulk flow. The endodermal layer in the roots probably provides the osmotic barrier.
• Halophytes in which the salt concentration with in the plant does not increase during the growing season are known as salt regulators. Often salt enter the plant, but the leaves swell by absorbing water, so concentration don’t increases. This leads to development of succulence (ratio of high volume/surface), a common morphological feature of halophytes.
• Sometime excess salt is exuded on the surface of the leaves, helping to maintain a constant salt concentration within the tissue. In some halophytes, there are readily observable salt glands on the leaves.
• Frequently, halophytes synthesis large quantity of the amino acids ie proline as well as other amnio acid and such other compounds as galactosyle glycerol and organic acid, these functions as osmotic adjustment.
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