Production Practices and Quality Assessment of Food Crops. Vol. 1

Modelling Fruit Quality 59
Figure 4. Simulation with SUGAR of seasonal variation in peach sweetness due to each sugar and
total sweetness.
its high sweetness rating. Sucrose was the main sweetener after the hundredth day
after bloom when fruit flesh contained large amounts of sucrose.
In conclusion, the carbon flow approach used in SUGAR is useful to model sugar
accumulation and synthesis during the growth of organs accumulating sugars. It may
be easily applicable to other fruit species which do not accumulate starch, such as
plums or apricots, but the same approach could be applied to starch accumulating
organs. Only mean temperature, flesh water content and dry flesh mass growth curve
data are required.
4.2. Modelling fruit quality with regard to source-sink relationships within
4.2. the plant
Models of carbon assimilation and allocation which include light interception have
been proposed for deciduous fruit crops (Seem et al., 1986; Abdel-Razik, 1989;
Buwalda, 1991; Wermelinger et al., 1991; Grossman and DeJong, 1994). Such
models are useful but they consider the tree as composed of compartments corresponding
to the various organs (fruits, leaves, stems, roots, etc.) without describing
the within-compartment variability. This serious limitation can be addressed by
considering a lower organisation level than that of the tree. Shoots bearing fruit
are convenient sub-units because they are large enough to subsume the most
important physiological processes on the one hand, and they are the basic units
for the most important horticultural interventions on the other. Moreover, they can
be considered as relatively autonomous sub-units in terms of carbon flow (Sprugel
et al., 1991). Thus, we propose that the shoot bearing fruit is a useful unit for
understanding the within-tree variability, and we suggest that modelling isolated
shoots is needed as a first step for the sake of clarification.
We present hereafter a simulation model of carbon assimilation by sources and