Physiological parameters for modelling differences in canopy development between sugarcane cultivars.

Abstract

For crop models to be used as an aid to plant improvement programmes, they should adequately represent cultivar traits. Biomass production depends on photosynthetically active radiation (PAR) intercepted by the canopy. Canopy development depends on the production and senescence of tillers and leaves on tillers, processes that are controlled mainly by temperature and PAR. Cultivar traits could be simulated by physiological parameters where these are stable across environments, show significant differences between cultivars and have physiological meaning. Our aim was to quantify cultivar control of canopy development by defining key physiological parameters and determining the values for these in sugarcane cultivars ZN6, ZN7, N14 and NCo376 grown in Zimbabwe. The parameters studied were thermal time requirements for shoot emergence, leaf and tiller appearance, surface area and leaf number of the youngest biggest leaf, PAR transmission at the start of tiller senescence and PAR extinction coefficient. The potential use of a new phyllochron reference point as a cultivar parameter is discussed. Cultivar ZN7 had the highest and NCo376 the lowest rate of leaf emergence. Cultivar N14 had the largest and NCo376 the smallest leaves. Low stalk population cultivars ZN6 and ZN7 initiated tiller senescence at higher levels of transmitted PAR than higher population cultivars N14 and NCo376. Results indicated that cultivars with higher tiller production rates were more efficient in capturing PAR. The importance of traits such as leaf size and canopy architecture was secondary.