Agriculture Reference
In-Depth Information
Fig. 11.1.
The percentage of true hermaphrodite, hermaphrodite with functional
stamens (male), and non-functional pistil and carpellodic
fl
owers at different times
of the year, on 'Solo'-type papaya tree growing in Honolulu with a mean minimum
temperature of 21°C and maximum temperature of 27°C (Awada, 1958).
<17°C can have 100% carpellodic fl owers. At higher temperatures (>35°C),
bisexual cultivars often become functionally male, with poorly developed and
non-functional female parts. This tendency varies with cultivars and within a
cultivar. Net photosynthetic rate also rapidly declines above 30°C.
Temperature during the growing season signifi cantly infl uences fruit
growth and development from the normal 120-150 days (Fig. 11.2). The
ef ect is most pronounced in subtropical areas. In these areas, fruit set does not
normally occur in winter, and fruit set before the winter can take up to 90 days
longer to reach maturity. Final fruit size is determined in the fi rst 4-6 weeks
of fruit development, and temperature plays a dominant role in the process,
especially in subtropical areas. Fruits that develop in the cooler season have
lower total soluble solids and fi nal fruit size.
Radiation
Papaya in its wild state is found developing as a rapid volunteer in areas
where the tree vegetation has been disturbed. The high saturation point above
1000 μmoles/m
2
/s (photosynthetic photon fl ux) (
ca.
800 W m
-2
) supports its
rapid development in areas having direct sunlight in newly disturbed areas.
No photoperiodic ef ects on tree growth, production or sex expression have
been reported (Lange, 1961). When exposed to shade, the plant is shorter,
