BIOSALINE AND ROLE OF HALOPHYTES
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By Dr. S.M. ALAM

Nov 01 - 07, 2004
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Agricultural land all over the world is deteriorating day by day for a variety of reasons, such as salinization, alkalinization, erosion, acidification, pulverization, compaction and petrification. Salt-affected soils of our country are posing a major threat to the agricultural productivity and must receive our utmost attention. To the possible extend, reclamation, drainage and irrigation management schemes must be utilized to minimize this threat to an irrigated agriculture. In the meantime, salt tolerant crops through research must be identified or developed that can produce economic yields even under saline conditions. A part of the salt-affected lands, termed as 'problematic soils' characterized by high salinity and sodicity, poor fertility, low intake water rates, underlain within brackish underground and with no access to good quality water are totally unfit to support economical agriculture. Such lands instead of being abandoned should also be put to an economical use by employing the biosaline approach through growing of salt tolerant trees, bushes and grasses which are commonly known as halophytes with the irrigation application of poor quality groundwater. It is estimated that about 2 million hectares (mha) area of land fall under this category in the country.

Halophytes are plants, which are capable of making good growth and development in saline soils. They manage from grass through shrubs to trees and occur in environments as diverse as coastal swamps inland marshs and extensive arid plains. Halophytes not only possess highly salt tolerance, but in some cases, are highly tolerant to water logging and in others of drought. These plants can be grow successfully and productivity under a variety of conditions which are not suitable for conventional agricultural crops. The capacity of plants to tolerate high levels of salinity depends on their ability to exclude salt from the shoot or to tolerate high concentrations of salt in the leaf. While most halophytes depend on a combination of both mechanisms to survive in extremely saline environment, non-halophytes and in particular most crop species have mainly been characterized as salt-tolerant or salt-sensitive on the basis of Na+ exclusion capability. Under saline conditions, a reduction in growth is a consequence modifications of ion balance, water status, mineral nutrition, stomatal behaviour, photosynthetic efficiency and carbon allocation and utilization.

The salt-tolerant shrubs, trees and grasses have become increasingly valuable resources for arid and saline land. These salt-tolerant plants (halophytes) provide forage for livestock and wildlife in rangelands throughout the world. Furthermore, many have been shown to be adaptable to genetic manipulation by selection or breeding. The introduction of genetic traits from hardy species into less hardy boot more desirable species has been investigated in many halophytes. Native species of saltbush are salt, drought, and heat-tolerant, easily cultivated highly productive, nutritious and palatable and they make attractive ornamentals. The recognition of that some halophytes can be adapted to agriculture has led to experiments in marginal soils. Many salt-tolerant shrubs and grasses have been tested on mine spoils, oil-fields locations and other drastically disturbed sites. Success in the re-vegetation of such sites involves tolerance to heavy metals, salts and drought, seedling survival under prolonged stress, rooting characteristics that ensure deep zone exploitation of water and nutrients.

Many products useful to humans can be derived from halophytes. Jojoba is a salt-tolerant shrub that produces a high-quality wax used in cosmetics and industrial products. A number of halophytic grasses and composites produce edible seeds. Several species, most notably guayule produce latex in usable quantities. There are some drawback to their use. Some palatable shrubs can be toxic to livestock, when consumed in excess. For example, salt bush and other shrubs may accumulate toxic concentrations of oxalates, and halogeton is a well-known poisonous halophyte. Pickleweed is a succulent shrub that absorbs soil ion for osmotic adjustment and it grows best under saline conditions.

 

 

In Pakistan, research has been conducted on various aspects of adaptation, establishment, productivity and animal utilization of these plants by various agriculture institutes of the country. Better understanding of the diverse adaptation of halophytes to salinity should aid agriculturists in selecting for increased salt-tolerance in existing cultivated species, and perhaps in the development of new crops.

SALT-TOLERANT TREES, BUSHES AND GRASSES (HALOPHYTES)

S. NO.

NAME

TOLERANCE

TREES

1.

Eucalyptus camaldulensis (Saphaida)

Tolerant to salinity, water logging and drought

2.

Eucalyptus rudis (Saphaida)

Tolerant to salinity, water logging and drought

3.

Eucalyptus miccrotheca (Saphaida)

Tolerant to salinity, water logging and drought

4.

Eucalyptus tereticornis (Saphaida)

Tolerant to salinity, water logging and drought

5.

Tamarix aphylla (Frash)

Highly tolerant to salinity

6.

Terminala arjuna (Arjan)

Tolerant to salinity and water logging

7.

Salix balulonica (Baid)

Tolerant to salinity

8.

Pogamia pinnata (Sukhchain)

Tolerant to salinity

9.

Acacia nilotica (Kikar)

Tolerant to salinity and sodicity

10.

Acacia tortilis (Kikar)

Tolerant to salinity and sodicity

11.

Acacia ampliceps (Kikar)

Tolerant to salinity and sodicity

12.

Albizzia lebbeck (Siris)

Tolerant to salinity

13.

Eugenia jamolana (Jaman)

Tolerant to salinity

14.

Zizyphus jujuba (Ber)

Tolerant to salinity

15.

Pridium guajava (Guava)

Tolerant to salinity

16.

Prosopis juliflora (Jangli kikar)

Highly tolerant to salinity and sodicity

17.

Prosopis chilensis (Jangli kikar)

Highly tolerant to salinity and sodicity

18.

Prosopis alba (Jangli kikar)

Highly tolerant to salinity and sodicity

19.

Leucaena leucocephala (Iple iple)

Tolerant to salinity

20.

Salvadora oleoides (Van)

Tolerant to salinity

21.

Phoenix dactylifera (Date palm)

Tolerant to salinity

22.

Prosopis spicegera (Jand)

Tolerant to salinity

23.

Capparis aphylla (Karir)

Tolerant to salinity

24.

Azadirachta indica (Neem)

Tolerant to salinity

25.

Grevia asiatica (Falsa)

Tolerant to salinity

BUSHES

1.

Suaeda fruticosa (Lana)

Tolerance

2.

Salsola soda (Sajji)

Tolerance to salinity/sodicity

3.

Kochia indica

Tolerance to salinity/sodicity

4.

Atriplex amnicola (Salt bush)

Tolerance to salinity/sodicity

5.

Atriplex lentiformis (Salt bush)

Tolerance to salinity/sodicity

6.

Atriplex undulata (Salt bush)

Tolerance to salinity/sodicity

7.

Maireana aphylla (Blue salt bush)

Tolerance to salinity/sodicity

8.

Maireana ammona (Blue salt bush)

Tolerance to salinity/sodicity

9.

Maireana pyramidata (Blue salt bush)

Tolerance to salinity/sodicity

10.

Simmondsia chinensis (Jojoba)

Highly tolerant to salinity

GRASSES

1.

Leptochloa fusca (Kallar grass)

Highly tolerant to salinity/sodicity

2.

Sesbania aculeate (Jantar)

Tolerant to salinity

3.

Panicum maximum (Bufallo grass)

Tolerant to salinity/drought

4.

Brassica napus (Gobi sarson)

Tolerant to salinity/drought

5.

Elitrigia elongata (Tall wheat grass)

Tolerant to salinity

6.

Finger millet (Madhal)

Tolerant to salinity

7.

Garden cress (Halon)

Tolerant to salinity

8.

Japanese millet (Swank)

Tolerant to salinity

9.

Parthenium argentatum (Guayule)

Highly tolerant to salinity