An analysis of leaf growth in sugar beet.

SUMMARY The expansion and persistence of leaves of sugar beet ( Beta vulgaris ) were measured in a series of crops grown in five seasons between 1978‐82 to establish how their growth varied between seasons, was affected by certain agronomic treatments and contributed to changes in leaf area index. Thermal time (accumulated temperature above 3°C) rather than days from sowing was used as a basis for comparing growth in different seasons. Leaf size depended on position on the stem and was influenced by sowing date, nitrogen fertiliser rate, plant population and the development of crop water stress. Changes in size were mostly associated with changes in the rates, rather than the duration, of expansion. When compared across seasons, the rate and duration of expansion of individual leaves were strongly negatively correlated so leaf size tended to be a more stable characteristic than either of its determining components. Nevertheless, final leaf areas varied by as much as 20% between seasons and this variation was attributable more to the temperatures experienced by leaves prior to unfolding and to the amounts of nitrogen present in the shoot at that time than to conditions during the main period of leaf expansion.