Agriculture Reference
In-Depth Information
Fig. 11.5.
Growth rate of papaya stem circumference, dry weight of the most
recently matured leaf petiole and the 17th leaf from the 2.4 cm juvenile leaf under
dry land conditions of Puna, Hawaii. The dry weight reduction in April is attributed
to low rainfall in the previous 2 months (Awada, 1977).
reversal and morphological changes in various degrees under the infl uence
of environmental changes (Storey, 1958). Type V staminate fl owers may
form functional ovaries and bear fruit during cool months. Type III fl owers
can form carpelloid fruit when exposed to low temperatures about 40 days
before anthesis.
The appearance of a large number of modifi ed fl ower forms occurs in
progenies from appropriate hybridization when grown under a temperature
regime that may range from around 13 to 32°C. Therefore, recovery of
extreme sex modifi cations may not be seen in a breeding programme unless
conducted in an area with wide fl uctuations in seasonal temperatures in
highly heterozygous parental types. Stamen carpellody is expressed under cool
temperatures, with increasing severity as temperatures lower in the
ca
40 days
before anthesis (Fig. 11.1). Instead of ten stamens in a double whorl, there are
only fi ve stamens, with the other fi ve fi xed to the normal carpels. The fruits
that develop from this carpellody are severely misshaped and unmarketable
(Fig. 11.6). Female sterility occurs under warm temperatures, again with
increasing severity at higher temperatures in the
ca.
40 days before anthesis.
Excessive nitrogen and moisture also favour stamen carpellody, while plant
stress such as N defi ciency and moisture stress infl uences female sterility
(Awada and Ikeda, 1957).
