International Journal of Horticulture, 2017,Vol.7, No. 23, 205-218
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point from first interim, second interim, final harvest are available from plants with seed weight 800 g. Lowess
regression is a nonparametric smoothing technique, see e.g., Cleveland (1981). These set of
(x, y)
points is now
lowess regressed at the first stage with
f
= 0.35 to obtain smoothed
(x, y)
values in computation of proliferation
rates. For yam yield
y
with seed weight 800 g, and growth curve shown in Figure 2, the proliferation rate is
obtained in Figure 8. Computation is based on a technique proposed in Dasgupta (2017c), with exponentially
decaying weights attached to empirical slopes computed from data pairs at different time points with respect to a
fixed time point
t
of interest. More weights are given to data points near the time
t
in derivative computation, and
less weights are assigned to distant time points from
t
. Weighted mean of these empirical slopes at derivative
stage is divided by
y
, and the empirical rates are smoothed by smooth. spline with spar = 0.00001 in S Plus to
obtain proliferation rate at time point
t
. The curve in Figure 8 has a sharp upturn from the beginning, then it
remains relatively steady with high values of proliferation rate in a region near the peak that looks like a hump;
and then the curve gradually decreases towards zero with progress of time.
Figure 9 Proliferation rate of yam (650 g): 2nd interim cut, wt. exp (-.01 x); spline
The proliferation rates for seed weight 650 g is drawn in a similar manner like Figure 8. The curve in Figure 9
reaches a peak at a later time point compared to that for seed weight 800 g. The peak is sharp unlike that for 800
g. The rise is slow to the peak and the fall from peak towards zero is sharp.
Figure 10 Proliferation rate of yam (500 g): 2nd interim cut, wt. exp (-.01 x); spline
The proliferation rates for seed weight 500 g shows increasing trend over almost the entire period of lifetime. The
rate is sharper after 100 days, and becomes steady towards the end. Starting with negative proliferation rate at
start, these plants seem to gradually adapt with harsh agro-climatic environment with progress in time. If the
same rate could be maintained in an extended plant lifetime with supporting nourishments to these plants, then
