International Journal of Horticulture, 2017,Vol.7, No. 23, 205-218
217
aboveground variable easy to measure. Proliferation rate in these interim time points is linearly interpolated from
time points of recorded growth data on that plant of specified seed weight and associated proliferation rates. The
proliferation rates are available for fixed seed weight and these are used in drawing Figure 8, Figure 9, and
Figure10.
If a plant height is recorded at a relevant time point, then that is taken into account. Otherwise the plant height at
that time point is interpolated from immediate upper and lower value of time when height is recorded in that
plant.
For the same time point counted from sprouting, there may be several different heights from different plants with
a fixed seed weight; we have taken all these different heights into account in the R program. A three dimensional
picture of proliferation rate of yam yield with time and plant height for plants with yam detachment at second
interim growth recording reveals that high value of proliferation occur for general plant height at about 120 days.
If the plant height is high in less time, the rate is high. The same is true if plant height is moderate in large value
of time. Plant height usually goes up with time and then it decreases slowly with time when plants mature at old
age. When seed weight of the yam corms planted are unknown or not recorded, then the above picture is of help
to ascertain the growth status of yam underground, based on the observable plant height.
Figure 13
Proliferation rate of yield vs. time & canopy radius: 2nd interim cut
Canopy radius of yam plants is an easy to measure and important variable that is sensitive to plant stress. In a
similar manner of drawing Figure 11, Figure 12, we draw Figure 13 on proliferation rate of yield vs. time &
canopy radius. At a particular time point there may be several different canopy radii for different plants with fixed
seed weight, we have taken all those different canopy radii into account in the R program. A three dimensional
picture of proliferation rate of yam yield with time and canopy radius for plants with yam detachment at second
interim growth recording reveals that high value of proliferation occur for moderate value of canopy radius. For
canopy radius around 40 cm, rate is moderately high after a time lapse from sprouting. For large canopy radius,
rate attains high values relatively early. Canopy radius usually goes up fast with time in the beginning and then it
decreases slowly over time when plants mature at old age. Like the earlier stated situation, when seed weight of
the yam corms planted are unknown or not recorded, the Figure 13 is of help to ascertain the growth status of
yam underground, based on observable aboveground variable canopy radius.
Maximum girth at the top of stem, over different stems in a plant is also easy to measure and coefficient of
variation of this variable is highest, when measured at three locations viz., top, middle, and base of stems. In a
similar manner of drawing Figure 11, Figure 12, Figure 13, we draw Figure 14. Proliferation rate is high in
general, when girth is around 6 cm. In the middle of lifetime, if the girth is approximately 5 cm, then the rate is
high. The upper edge of proliferation surface showing line of peaks corresponds to time 110 days. Figure 14 is of
similar pattern with that of Figure 13. Top of the stem is a well defined position to measure girth. In contrast, base
position is affected by variation over time in level of ground soil, which also affects the middle position in a stem
while taking growth readings.
