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silique number, seed number, seed weight, biomass, number of viable seeds (all P < 0.001),
and seed number per silique (P < 0.05) than NC plants. The clipping effect was less evident in
the s econd ex periment; i n t his cas e C P p lants h ad f ewer s iliques, l ighter s eed w eights, a nd
lower biomass than NC plants (Figure 3.5, Table 3.5). Clipping had no effect on flowering
date, number of viable seeds, or the resource allocation index in either year (Table 3.5).
Effect of the percentage of simulated insect-resistant plants
In the 2008 experiment, an increased percentage of NC plants resulted in reduced seed
weight, biomass, and number of viable seeds in both plant types (P < 0.01 for all variables),
though t he pr esence a nd m agnitude o f t his e ffect varied w ith pl ot pos ition. T here was no
effect o n f lowering t ime o r t he r esource al location i ndex. T here w as al so a s ignificant
interaction between leaf clipping, the percentage of NC plants, and plot position (Table 3.5),
suggesting that NC and CP plants reacted differently to different combinations of conditions.
In t he p lot cen tre, an i ncreased p ercentage o f N C p lants resulted i n d ecreased s eed w eight,
biomass, and number of viable seeds of both plant types. However, at the plot border, these
variables only decreased for NC plants (Figure 3.6, Table 3.6). Each of these variables was
plotted against the percentage of NC plants separately for each plant type at the border, and
again f or t hose a t t he c enter of t he pl ots ( Figure 3 .6). T he r egression s lopes di d not di ffer
between NC and CP plants situated at the center of the plot. The slopes for NC plants situated
at the border did not differ from those situated at the centre. In all cases, the low values of the
regression coefficient R 2 indicated a poor fit and a great deal of variability among plots (Table
3.6).
In the 2009 e xperiment, there was no l ink between the percentage of NC plants and
any of the measured characteristics, and no interaction among treatments. There was only one
significant lin ear r egression; f lowering d ate o f th e N C p lants s ituated a t th e p lot c enter
increased with the percentage of NC plants (Figure 3.6).
In the 2008 e xperiment, the relationship between the variables and percentage of NC
plants was non-linear for CP plants at the plot border ( Figure 3.6). The resource allocation
index was lowest at T 50 for all NC and CP plants at both plot positions (Figure 3.6). In the
2009 experiment, the relationship between the variables and percentage of NC plants was also
non-linear for both NC and CP plants at the plot center. In this experiment, extreme values of
NC plants were observed at T75 in the plot border and the resource allocation index of NC and
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