Nitrogen fertilizer and foliar application of cytokinin affect spikelet and floret set and survival in oat

Abstract

Yield potential of oat is only partly realized and both formation and expression of yield potential are largely environment dependent. This study was designed to monitor the possibilities for and efficacy of foliar applications of a synthetic cytokinin growth promotor (benzyl-aminopurine, BA) to enhance formation and realization of yield potential in oat ( Avena sativa L.). Comparison was made at 0 and 80 kgNha −1. BA was applied (0 and 10 −3 g a.i. 1 −1 at 300 L ha −1) when the apex was at the stage of initiation of floret abortion (i.e., close to booting stage). Three cultivars were included in the main field trials conducted at the Viikki Experimental Farm, University of Helsinki, Finland, in 1994 and 1995. Grain yield and 25 morpho-physiological traits were recorded. An additional BA-concentration response study was carried out using a modern cultivar (in 1994) and BA concentrations ranging from 10 −9 to 10 −1 g a.i. 1 −1. In both experiments, foliar applications of BA increased set of sterile spikelets. An increase in set of fertile spikelets and florets was recorded only in the BA response study between 10 −8 and 10 −3 g BAl −1. Nitrogen fertilizer application induced similar effects with the exception that set of sterile spikelets was not enhanced. In the BA response study, spikelet abortion increased with increasing BA application rate as numbers of sterile spikelets per panicle increased. Nitrogen applications increased chlorophyll content of the flag leaf and prolonged maturation, whereas BA treatment produced no consistent effects. Nitrogen fertilizer application increased panicle and grain filling and delayed senescence, but did not reduce abortion of spikelets and florets.