Vol. 77 No: 4

Title:
Tuber dry-matter accumulation of Zantedeschia in response to temperature and photosynthetic photon flux

Authors:
KEITH A. FUNNELL, ERROL W. HEWETT, JULIE A. PLUMMER and IAN J. WARRINGTON

pp: 446-455

Abstract:
Dry-matter accumulation and partitioning in plants of Zantedeschia ´Best Gold` were quantified under a range of temperature and photosynthetic photon flux (PPF) regimes using plant growth analysis. Initiation of tuber growth did not require an obligate environmental trigger. Under both PPF regimes, relative growth rate of the tuber (RGR_T) increased linearly with increasing temperature (13 to 28°C) up to a maximum at 28°C, with a base temperature of 3.2 ± 1.1°C. Optimum temperature for tuber growth was found to be PPF dependent, but maximum tuber dry mass was calculated as occurring under low PPF (348 µmol m^-2s^-1) at 24.5 ± 0.1°C. Mechanisms of acclimation under both PPF regimes suggested that tuber growth was principally source limited. Source limitation was expressed either in terms of: 1) enhanced inter-sink competition for assimilates, as occurred under the low PPF regime. where leaf area development was in direct competition with tuber growth (RGR_T) or, 2) efficiency of dry-matter accumulation by the leaf area present, as occurred under the high PPF regime, where large increases in RGR_T were correlated with increased net assimilation rate (NAR). Use of the daily increment of dry matter into tuber tissue (TMP) provided a more sensitive measure of short-term changes in partitioning than the conventionally used term, harvest index.

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