Em. Kahangi et al., EFFECT OF NATURAL AND ARTIFICIAL CHILLING IN CARROT DAUCUS-CAROTA L AT DIFFERENT LOCATIONS IN KENYA .1. EFFECTS ON BOLTING AND FLOWERING, Journal of Horticultural Science, 71(5), 1996, pp. 807-812
Effect of natural chilling and artificial chilling durations of 2-8 we
eks at 9 degrees C on percentage bolting and flowering and on days tak
en from planting to the two events in carrot cv. Nantes was observed a
t four locations in Kenya in 1991/92. These were; Juja (1500 m above s
ea level in a warm Upper Midland (UM) zone) and Mole (2454 m), Kinango
p (2558 m) and Marindas (2804 m), all in an Upper Highland (UH) zone.
The observation was repeated in 1992/93 but in Juja and Kinangop only.
In 1991/92 the lowest bolting and flowering percentage (<25%) was rec
orded in carrot plants whose stecklings had received natural chilling
at all planted sites while in those whose stecklings had received arti
ficial chilling, bolting and flowering percentage increased with artif
icial chilling durations within each location. Over 75% flowering was
obtained only in those plants grown from carrot stecklings chilled for
six and eight weeks within each location and in those given four week
s chilling at Kinangop. In 1992/93,the results were quite opposite fro
m those of the previous year at Kinangop when 100% bolting and floweri
ng was obtained in all chilling treatments including the naturally chi
lled plants. But at Juja bolting and flowering in 1992/93 was similar
to the previous year. Days from planting to 50% of final bolting and f
lowering decreased with increased durations of chilling at all sites,
in both years. Days to final bolting and flowering followed a similar
pattern. The control plants bolted and flowered earlier than those giv
en two weeks of chilling in 1991/92 and at the Kinangop site in 1992/9
3. Significant differences (P<0.05) in days taken to bolting and flowe
ring were observed between locations especially in 1992/93 when Juja p
lants bolted significantly earlier than those at Kinangop in most trea
tments.