Agriculture Reference
In-Depth Information
Fig. 4.29.
Responses of onion bulbing to light conditions. (a) Bulbing of cv.
'Hyton', a Dutch long-day hybrid for spring sowing, and cv. 'Keepwell', a Japanese
intermediate-day hybrid, autumn-sown in the UK, after 70 days at a range of
constant daylight photoperiods. (b) Four cvs of decreasing day-length requirement
for bulbing, R > A > K > E, after 40 days in 18 h photoperiods of light of red:far-red
ratio (RFR) 2.2 (left group) or 0.65 (right group) (Mondal
et al.
, 1986b. Photographs
courtesy of Warwick HRI).
Fig. 4.30.
Relationships between the rate of onion bulbing and photoperiod and
temperature for the spring-sown cv. 'Hyton' (a) and the autumn-sown cv. 'Keepwell'
(b) derived from experiments in a range of daylight photoperiods and controlled
temperatures (see plants in Fig. 4.29a). Rate of bulbing was calculated as the
reciprocal of the time (days) for the first bladeless bulb scales (see Fig. 4.26) to be
detectable.
