RESPONSES OF 3 ARID ZONE GRASSES TO N-DEFICIENCY - A GREENHOUSE STUDY

Responses of three arid zone grass species Cenchrus pennisetiformis Ho chst. & Steud., Dichanthium annulatum (Forssk.) Stapf., and Panicum tu rgidum Forssk. to five N levels (224-control, 112, 56, 28. and 14 mug mL-1) were examined. Biomass production and growth rate of D. annulatu m were not as affected under N-deficient regimes as the other two spec ies. D. annulatum maintained almost uniform shoot N concentration and chlorophyll contents at all assessed N levels, whereas a reduction in these two variables was found in both C. pennisetiformis and P. turgid um. Leaf soluble proteins increased considerably in P. turgidum (30.5- 45.5% compared to control) and decreased in D. annulatum (19.58-36.98% compared to control), whereas they remained unaffected in C. penniset iformis. Leaf free amino acids and soluble sugars decreased consistent ly in the three species. D. annulatum was found to be highly efficient in N utilization under N-deficient regimes compared with C. penniseti formis and P. turgidum. High adaptation of D. annulatum to N deficienc y may have been attributable to its perennial growth habit. Common ann ual growth habits of the remaining two species preclude them from expe riencing N deficient conditions. which might explain their poor adapta tion to low N regimes.