Date of Award

11-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr.Synan AbuQamar

Second Advisor

Dr. Taoufik Ksiksi

Third Advisor

Dr. Ali A.M. EI-Keblawy

Abstract

Halophytic C4 grasses, including Sporobolus species, have developed specific mechanisms to cope with salinity stress. Among these, “salt glands” which are bi- cellular leaf epidermal structures eliminating excess saline ions from shoots by excretion under salinity stress. Salt glands are morphologically visible and can potentially be used for salt tolerance breeding programs. The objectives of this study were: (1) to determine the leaf salt gland excretion rates of United Arab Emirates native halophytic chloridoid grass species, S. spicatus and S. arabicus; (2) to determine if leaf salt gland excretion rate and density can effectively predict salinity tolerance among Sporobolus genotypes, by correlating excretion data of salinity tolerance data from another study; and (3) to quantify morphological differences in salt gland structure between the most tolerant and the least tolerant genotypes in each species for salinity. Forty-five grass genotypes were exposed to 15,000 ppm NaCl and measured excreted leaf Na+, K+ and Cl- concentrations from mature leaves by using flame photometer and Chloride ion selective electrodes. Parameters were expressed as mmol ion g -1 leaf fresh weight. Week. Selected four genotypes under non-saline conditions were compared for salt gland density, salt gland size and morphology via scanning electron microscope. Bi-cellular salt glands were observed on both leaf surfaces and the glands were protruded, globular and semi-sunken. S. arabicus genotypes had larger sized salt glands than S. spicatus genotypes. S. spicatus genotypes had higher leaf salt gland ion excretion rates and density than S. arabicus genotypes. Salt gland ion excretion rates and density were positively correlated with salinity tolerance. This suggests that ion excretion activity is an important salinity tolerance mechanism and gland density is an important potential trait for determining salinity tolerance between the two Sporobolus species. Information gained from this study could be used as the basis for future investigations to understand the primary salinity tolerance mechanism in Emirati native halophytic grass.

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