Effect of Different Nitrogen Sources on Growth, Reproduction, Amino Acid, Fat and Sugar Contents in Ulva fasciata Delile (Part III)

Abstract

This investigation includes a study of the effect of some nitrogenous sources namely urea and potassium nitrate on the growth, reproduction, amino acid synthesis, fat and sugar Contents in Ulva fasciata plants. The results showed that Ulva fasciata plants preferred urea rather than nitrate for its growth and amino acid synthesis. Either urea or nitrate caused a fall in the total fat content, but sugars revealed a slight response. Rieh nitrogen supplies favoured asexual reproduction while the sexual reproduction was enhanced by nitrogen depletion.

Assessment of macroalgal nitrogen limitation in a seasonal upwelling region

“…Ulva spp. can use urea and amino acids as nitrogen sources (Nasr et al 1968, Mohsen et al 1974). However, in general the capacity of macroalgae to utilize organic forms of N is very limited (Stephens 1981).…”

Nitrogen ecophysiology of intertidal seaweeds from New Zealand: N uptake, storage and utilisation in relation to shore position and season

“…Carpenter et al 1972, Bekheet & Syrett 1979, Price & Harrison 1988. For macroalgae, the current knowledge of urea utilisation is restricted to the ability of urea to sustain the growth of a number of seaweeds (Nasr et al 1968, Mohsen et al 1974, Adamich et al 1975, Hanisak 1979a, Probyn & Chapman 1983, Mairh et al 1999, Navarro-Angulo & Robledo 1999, Lotze & Schramm 2000 and the demonstrated uptake of urea by Chordaria flagelliformis (Probyn & Chapman 1982, 1983 but not by Ecklonia maxima (Probyn & McQuaid 1985). From the present study, it appears that urea is a seasonally important N source for 4 intertidal seaweeds in New Zealand, with the greatest contribution to overall N nutrition occurring in summer when ambient seawater N concentrations are minimal.…”

Gametogenesis, gametes and zygotes: An ecological perspective on sexual reproduction in the algae

“…In both unicellular and multicellular freshwater algae, nitrogen limitation has frequently been shown to stimulate gametogenesis (Sager & Granick, 1954;Ellis & Machlis, 1968;Hill & Machlis, 1970;Rayburn, 1974;Simona, Van Beem & De Vries, 1984;Hoshaw & McCourt, 1988). Low levels of nitrogen induced gametogenesis in Ulva, whereas high levels induced asexual reproduction (Mohsen et al, 1974). Although nitrogen is required for gametogenesis in Laminaria (Hsiao & Druehl, 1973a), this factor appeared less important than others under field conditions (Hsiao & Druehl, 1973b).…”