Botany and Improvement 13
meaning that separate plants bear either male, female or bisexual flowers. The
female and bisexual flowers are waxy, ivory white and borne on short peduncles in
leaf axils along the main stem. Flowers are solitary or small cymes of three individu-
als. Ovary position is superior. Prior to the opening, bisexual flowers are tubular and
female flowers are pear-shaped. Since bisexual plants produce the most desirable
fruit and are self-pollinating, they are preferred over female or male plants. A male
papaya is distinguished by the smaller flowers borne on long stalks. Female flowers
of papaya are pear shaped when unopened, and distinguished from bisexual flow-
ers which are cylindrical. Bisexual flowered plants are self-pollinating, but flowers
on female plants must be cross-pollinated by either bisexual or male plants flowers
(Morton 1987).
2.1.5 Fruit
Individual fruits mature in 5–9 months, depending on cultivar and temperature.
Plants begin bearing in 6–12 months. Fruits are large, oval to round berries, some-
times, called pepo-like berries since they resemble melons by having a central seed
cavity. Fruit are borne axillary on the main stem, usually singly, but sometimes, in
small clusters. The fruit is 15.0–50.0 cm long and 10.0–20.0 cm thick; weighing up
to 9.0 kg (Morton 1987). The skin is waxy and thin but fairly tough. When the fruit
is immature, it is rich in white latex and the skin is green and hard. As ripening
progresses, papaya fruits develop light or deep yellow-orange coloured skin, while
the thick wall of succulent flesh becomes aromatic, yellow orange or various shades
of salmon or red. It is then juicy, sweetish and somewhat like a cantaloupe in flavour,
but sometimes is quite musky (Morton 1987). Mature fruits contain numerous grey-
black ovoid seeds attached lightly to the flesh by soft, white and fibrous tissue. These
corrugated, peppery seeds of about 5.0 mm in length are each coated with a trans-
parent and gelatinous aril (Jaime et al. 2007).
2.1.6 Seed
Well-pollinated fruits result in 400–600 seeds per fruit. The embryo is straight
and ovoid, with flattened cotyledons. The seeds are coated by a mucilaginous mass
derived from the pluristratified epidermis of the outer integument. The embryo is
enclosed in a gelatinous layer (aril) known as sarcotesta at physiological maturity
(Ming and Moore 2014). A compact mesotesta and outer and inner integuments
can be observed underneath. The endosperm is composed of thin-walled cells
with abundant oil bodies and aleuronic grains, lacking starch at maturity (Teixeira
da Silva et al. 2007). Photosensitive seeds of wild papayas are dormant at matu-
rity, and their germination may be triggered by changes in light quality (Paz and
Vazquez-Yanes 1998).
Papaya seeds generally have been classified as the intermediate seed owing to
intermediate seed storage capacities and storage for periods greater than 5 years is
difficult (Ellis et al. 1991; Wood et al. 2000). Loss of viability has been reported at
moisture contents below 8.0%–10.0% (Ellis et al. 1990), although viability has been
reported when seed was desiccated to 5.0% moisture contents (Magill et al. 1994).