| dc.description.abstract | Four experiments were conducted to investigate effects of
temperature, humidity, soil water deficits, photoperiod and
sowing date on growth, pod-set and yield of different
varieties of pigeonpeas. The varieties were chosen to include
determinate (ICPL4, ICPL87, ICPL151) and indeterminate (ICPL81,
UPAS120) types.
Temperature and photoperiod treatments imposed from flower
initiation to harvest in a naturally lit glasshouse had
no effect on shoot and root dry weights, but the pod
number and grain yield were reduced except in one
genotype when the day temperature was increased from 300
to 400C. Variation in day/night temperatures showed that low
night temperature delayed flowering and inhibited podset.
Pod-set occurred at 30/150C and 30/250C day/night
temperature in ICPL4 and ICPL81 but no pod-set was observed
at 30/50 in a~l the genotypes
day temperature under growth
and at 30/150 in ICPL87. High
chamber conditions caused
complete flower abscission regardless of the night
temperature and high leaf shedding occurred which influenced
the biomass production.
High humidity and increased soil moisture increased leaf area
for ICPL87 but reduced that for ICPL81. At high humidity
the shoot dry weight decreased for ICPL81 at high soil
moisture but an increase was observed for ICPL87. The
flower number declined at high humidity and increased soil
moisture for ICPL87 but was not affected for ICPL81.
High humidity reduced the number of pods, percentage pod-set
and grain yield regardless of the moisture regime.
Delayed sowing at this site is characterised by declining
day-length, temperature, as well as rainfall. The results of
the sowing date experiment showed that delayed sowing led to a
decline in leaf area and shoot dry weight at flowering as well
as at maturity. Late sowing reduced the number of flowers,
pods, branches, and percentage pOd-set which led to a decline in
grain yield.
The following conclusions may be made from the results of this
work:
1. Increased day temperature reduced the grain yield as a
result of greater flower abscission and pod abortion. Both
day and night temperature are important for growth after
flowering and pod-set in the genotypes studied.
2. 'Severe' water stress can limit the yield of these
genotypes and the indeterminate genotype tolerated the
water-limited situation better than the determinate.
3. A major effect of the date of sowing at this location and
the genotypes used is the reduction in plant size due to
reduced branching and stem size. | en |
