14 Papaya
However, papaya seeds have been grouped as recalcitrant type by Chin et al. (1984)
and Hofmann and Steiner (1989). Propagation of papaya by seed is difficult due
to rapid seed deterioration after harvest. This is attributed to microbial degenera-
tion of the sarcotesta which reduces viability. Salomao and Mundim (2000) have
reported an orthodox behaviour. Due to dehydration up to 5.3%–6.9% moisture
content (MC), followed by exposure to sub-zero temperatures and treatment with
GA 3 were the most favourable combined treatments to enhance papaya seed ger-
mination. This type of seed nature has permitted germplasm conservation in con-
ventional and cryogene banks. Wood et al. (2000) have reported that dormancy
results from desiccation of papaya seeds and that desiccation-induced dormancy
can be reversed by heat shock. Poor germination of papaya seeds after drying to
4.5%–11.5% MC is due to the induction of dormancy rather than a loss in viability.
Desiccation-induced dormancy can be removed by heat-shocking rehydrated seeds
for 4 h at 36°C before return to a 26°C germination regime. Both the endosperm
and embryo of intermediate seeds of papaya display an O:S ratio within the range
of values found for orthodox seed tissues.
2.2 Floral Morphology...................................................................
The inflorescence of a male plant is long, pendulous panicle bearing many flowers.
Male flowers are small, about 2.0–3.0 cm long, and have a minute calyx of five small
united sepals, and a long corolla and tube divided about one-third of the way from its
mouth into five pointed lobes. The pale yellow corolla is often fragrant; at the mouth
of the tube 10 epipetalous stamens are arranged in two rows of five, one row with
longest filament lying opposite with the petal lobes, the other with shorter filaments
lying opposite the lobes (Figure 2.1).
FIGURE 2.1 Floral diagrams: staminate (a), pistillate (b), normal hermaphrodite (c) and
elongata hermaphrodite (d).