13
Duncan et al. (1978) calculated the crop growth rate
of 'Florunner' from the same data used by McGraw. Linear
regression of crop dry weights from canopy closure at 55
days until seed growth became significant at 70 days deter-
2
mined that the crop growth rate was 21.2g/m /day. This was
assumed to be the period of maximum crop growth rate.
Partitioning was used by Duncan et al. (1978) to
refer to the division of daily assimilate between reproduc
tive and vegetative plant parts. The partitioning factor
may be calculated by comparing the fruit and vegetative
growth rates. A correction is made for the fruit growth
rate to account for the additional energy expenditure of
seed production. Correction factors developed by Hanson
et al. (1961) and Penning de Vries ( 1974) are used to
compensate for the higher concentration of oils and proteins
in seeds. Duncan et al. (1978) estimated partitioning by 2
methods for 'Florunner'. From comparison of crop and
corrected fruit growth rates the reproductive partitioning
factor was calculated as 84.7%. The value for the repro
ductive partitioning factor estimated from simulations of
the PENUTZ model was 72% (Duncan et al. 1978).
Two useful terms often used to describe plant canopies
are leaf area index (LAI) and percent ground cover. Percent
ground cover is the percent of soil surface that is covered
by the crop canopy. The LAI is defined as leaf area per
unit of ground area and does not indicate directly the
amount of solar radiation intercepted by the canopy. Larval