Effects of photoperiod and temperature on sugars and fructans in leaf blades, leaf sheaths and stems, and roots in relation to growth of Poa pratensis

Abstract

Vegetative plants of Poa pratensis L. cv. Holt were cultivated in short days (SD; 8 h summer daylight) and in long days (LD; 8 h summer daylight + low intensity extension of 5 μmol m‐2 s‐1) at 12, 18 and 24°C in one experiment and at 9, 12, 15 and 18°C in another. Relative growth rate (RGR) as the mean of both experiments and all temperatures was 32% higher in LD than in SD between start of daylength treatment and first harvest, and 18% higher in LD than in SD between first and second harvest. Early in the daylength treatment period, more assimilates were allocated to storage in SD than in LD, so that at first harvest leaf sheaths and stems had 175% higher concentration of fructans in SD. Later this allocation pattern changed, and for the larger plants at the second harvest the differences in fructan concentrations were much smaller between the two daylengths. Both sugar and fructan concentrations were highest at low temperatures. The distribution of sugars and fructans varied from mostly sugars in the leaves to mostly fructans in leaf sheaths and stems and roots. The fructans were mainly high degree polymerization fructans. At least two series of fructans were present, and the dominant one was probably based upon kestose. It is concluded that allocation of assimilates to growth in leaf area instead of to storage may be important for the observed LD stimulation of dry matter production.