physiological responses of fennel (foeniculum vulgare l.) to water limitation

two field experiments were conducted at the research farm of the faculty of agriculture, university of tabriz, iran during 2009-2010 and 2010-2011, to evaluate the response of fennel (foeniculum vulgare l.) landraces to limited irrigation. experiments were arranged as split plot based on randomized complete block design in three replications with irrigation treatments (irrigation after 60, 90, 120 and 150 mm evaporation from class a pan) in main plots and landraces (hamdan, ezmir and gaziantep) in subplots. chlorophyll a, chlorophyll b and proline contents, soluble carbohydrates, relative water content and leaf water potential of fennel were recorded at flowering stage. the results showed that the all traits of fennel were significantly affected by limited irrigation. chlorophyll a, chlorophyll b, relative water content and leaf water potential decreased by 30, 24, 27 and 41%, but proline and soluble carbohydrate increased by 41 and 23%, respectively, due to water deficit. ezmir and hamdan were more drought tolerant than gaziantep land race. therefore, fennel plant uses osmoregulation by increasing proline and soluble carbohydrate in order to tolerate water limitation.