PJB-2013-337
ANATOMICAL ADAPTATIONS OF CYNODON DACTYLON (L.) PERS. FROM THE SALT RANGE (PAKISTAN) TO SALINITY STRESS. II. LEAF ANATOMY
MANSOOR HAMEED1*, MUHAMMAD ASHRAF1,2, NARGIS NAZ1, TAHIRA NAWAZ1, RIFFAT BATOOL1, M. SAJID AQEEL AHMAD1, FAROOQ AHMAD1 AND MUMTAZ HUSSAIN1
Abstract
Leaf anatomical modifications were examined in a naturally adapted salt tolerant population of Cynodon dactylon (L.) Pers., collected from a heavily salt affected soil in the vicinity of a natural salt lake, Uchhali Lake, in the Salt Range of the Punjab province of Pakistan. An ecotype of this grass was also collected from a normal non-saline habitat from the Faisalabad region, which was considered as a control. Both populations were subjected to salt stress in hydroponics. The salt treatments used were: control (no salt), 50, 100, 150 and 200 mM of NaCl in Hoagland’s nutrient solution. After eight weeks of growth in hydroponics leaf and leaf-sheath anatomical characteristics in the differently adapted ecotypes were studied. The ecotype from the Salt Range was much better adapted to salt stress than its counterpart from the Faisalabad region. Anatomical adaptations in the salt tolerant ecotype to saline environments were very specific, and these were not only for the excretion of toxic ions but also accumulation of ions in the parenchymatous tissue. The prominent adaptive features in the salt tolerant ecotype were increased development of vesicular hairs for the exclusion of toxic ions through leaves as well as less affected parenchymatous tissue (mesophyll, bundle sheath, and bulliform cells) due to salt stress. Additionally, some adaptations reflected were the development of xeromorphic characteristics (decreased stomatal area and size on adaxial leaf surface, less affected epidermis, increased bundle sheath, and increased bulliform cell area) essential for checking undue water loss. Highly developed dermal tissue, particularly lower epidermis and bulliform cells, and decreased stomatal density and area in the salt tolerant ecotype seemed to be crucial for checking undue water loss under critical limited moisture environments.
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