Morphological and physiological growth responses of Kentucky bluegrass to foliar applications of iron, a cytokinin, and growth regulator- like chemicals

A series of studies were conducted to examine morphological and physiological responses of Kentucky bluegrass (Poa prazensis L.) following foliar applications of chelated iron phosphate citrate (Fe), the synthetic cytokinin benzyladenine (BA), the systemic triazole fungicides propiconazole and triadimefon, and MZ63 cold water seaweed extract. Applications of Fe at 112 mg m⁻², BA at 6 mg m⁻², propiconazole and triadimefon at 42 and 150 mg m⁻², respectively, and MZ63 seaweed extract at 0.32 ml m⁻² enhanced root and shoot growth and development of seedling Kentucky bluegrass.

Repeated applications of BA, the triazoles, or MZ63 in late summer or fall and spring tended to slightly increase post-transplant rooting and sod strength of Kentucky bluegrass as compared to single applications. Repeated applications of Fe applied alone in late summer or fall and spring increased Kentucky bluegrass rooting as compared to single applications of Fe. However, the potential for reduced sod strength and post-transplant rooting was also indicated following single summer applications of chelated Fe at 112 mg m⁻².

Kentucky bluegrass growth from various combinations of BA, the triazoles, MZ63 seaweed extract and Fe were highly variable. The nature of the responses indicated the possibility of an adverse interaction between the growth promoting activities of chelated Fe and the other materials.

Kentucky bluegrass seedlings treated with Fe, BA, the triazoles, or MZ63 seaweed extract had increased photosynthetic rates on a land area basis, but not on a per gram shoot dry weight basis. These results suggested the larger photosynthetic rates were probably in response to an increased leaf area resulting from stimulation of leaf and lateral bud initiation.

Benzyladenine was the most active material in delaying the senescence-like response of excised Kentucky bluegrass leaves as measured by carbon dioxide exchange, percent chlorophyll fluorescence decay, and leaf color ratings. Applications of Fe or propiconazole also delayed excision-induced senescence of Kentucky bluegrass leaves, while the anti-senescence activity of triadimefon was highly variable. Combinations of Fe with BA or the triazoles did not further promote a delay in excision-induced senescence.