Summary — A 5-wk factorial experiment was conducted to examine the effects of osmocote (18N:11P:10K; commercial controlled-release fertilizer), rock phosphate and 3 species of arbuscular mycorrhizal fungi on the growth of the strawberry cultivar Senga Sengana in a peat-sand-vermiculite substrate. Three Glomus species, G98 (probably G intraradices), G128 (an undescribed species) and G geosporum were compared. G98 and G128 significantly increased shoot dry weights compared with the non-mycorrhizal control. Levels of root colonization by G98 and G128 were significantly greater than by G geosporum. The addition of both fertilizer types significantly increased shoot dry weights. Neither osmocote (0.5-2.0 g/l) nor rock phosphate (1.0-5.0 g/l) addition had a significant effect on colonization by the 3 fungi. An osmocote fertilizer applied at 25% of the minimum recommended commercial rate to mycorrhizal plants was sufficient to produce equivalent dry matter yields as non-mycorrhizal plants receiving the

Systematic and ecological implications were shown for Australian seagrasses by studies of isozymes, secondary compounds and experimental cultures. In Halophila, small- and large-leaved plants which occur sympatrically from northern Queensland to New South Wales and were referred to H. ovalis (R.Br.) Hook. f. differed in isozymes and secondary compounds and maintained leaf size differences in experimental cultures. The small-leaved plants should be referred to a different species. In Halodule, narrow-leaved plants that were referred to H. uninervis (Forsk.) Aschers. and H.pinifolia (Miki) Den Hartog were examined. In experimental cultures, narrow-leaved plants from Thursday Island produced both tridentate and rounded serrulate leaf tips and differed in isozymes and secondary compounds from wide-leaved plants. The narrow- leaved plants should be referred to H. pinifolia and the wide-leaved plants to H. uninervis. In Zostera, small- and large-leaved forms of Z. capricorni Aschers. which occur sympatrically in Queensland and New South Wales have similar isozymes that differ from those of Z. muelleri Irmisch. ex Aschers. of South Australia. Experimental cultures of Z. capricorni continued to produce 5-nerved leaves and those of Z. muelleri, 3- nerved leaves. In Amphibolis, cultures of A. antarctica (Labill.) Sonder & Aschers. and A. griffithii (J. M. Black) Den Hartog continued to show leaf differences but were similar in secondary compounds and isozymes, differing in only one of eight enzyme systems. In Posidonia, wide-leaved plants of P. australis Hook. f. continued to produce leaves in culture that differed in width from those of P. sinuosa Cambridge & Kuo but were similar in secondary compounds and isozymes, differing only in one of eight enzyme systems. The chemical evaluations and experimental cultures suggested wide differences in Halophila and in Halodule but indicated only narrow differences in the other three genera.