Effect of Cutting During Reproductive Development on the Regrowth and Regenerative Capacity of the Perennial Grass, Phalaris aquatica L., in a Controlled Environment

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Two cultivars of phalaris (Phalaris aquatica L.), Australian and Sirolan, were cut at four stages of development in a controlled environment to study factors involved in the sensitivity of phalaris to grazing during spring. Effects on tillering, regrowth after cutting and regenerative capacity after an artificially imposed summer dormant period were observed. Compared with Australian, Sirolan cut after the commencement of stem elongation was characterized by a higher degree of decapitation due to more synchronous elevation of its apices, and displayed a more severe reduction in regrowth, size of tiller bases and dormant buds and levels of carbohydrate reserves in summer relative to plants cut before stem elongation. Suppressed bud activity in tillers of Sirolan decapitated at early stem elongation, and the potential for profuse tillering associated with low bud dormancy after cutting at the early boot stage, could reduce persistence under field conditions. Relative to plants cut before stem elongation, regeneration growth after 'summer' by plants cut during reproductive development was depressed more severely for Sirolan (56-70%; P ⩽ 0·05) than Australian (28%; n.s), a result more closely related to regenerating tiller size than number. Regeneration growth did not differ significantly with stage reproductive development at cutting in either cultivar. Regenerative capacity of phalaris cut during reproductive development can be considered to depend on an increasing contribution from buds on bases of tillers decapitated when cut and a contribution from buds on intact tiller bases which declines as the stage of cutting becomes later. The balance between these source will depend on the environment.