18 Papaya
leaves considerable space between the stigmatic rays and the anthers. The anthers
may be 5.0–8.0 mm below the stigma. In these cases, most of the bagged flowers
fall. The problem may be alleviated by pollinating the flowers with pollen from the
male flowers that are usually produced on andromonoecious (hermaphroditic) trees
before bagging (Nakasone 1986). Studies on the Sunrise variety suggest occurrence
of cleistogamy in this variety. The time from pollination to first ovule penetration
was 25 h at 28°C temperature.
2.2.4 Pollinators...................................................................
Papaya requires pollination for set fruit. The pollination of the dioecious flowers is
primarily carried out by nocturnal moths known as hawk moths or sphinx moths
(Martins and Johnson 2009). Although papaya flowers are visited by hawk moths,
several beetles, skipper butterflies, bees, flies, and humming birds also visit papaya
flowers (Figure 2.2). The actual species of hawk moths vary from site to site but, in
general, any medium-to-large-bodied, relatively long-tongued species of hawk moth
can serve as major floral visitors/pollinators, namely Hippotion celerio, Herse con-
volvuli, Macroglossum trochilus, Daphnis nerii, Nephele comma due to fast-flying
and highly mobile insects, makes them efficient pollinators, whereas Ceoliades
sp. (Hesperiidae) and Sphingomorpha chlorea (Noctuidae) are occasional visitors
(Garrett 1995). Brown et al. (2012) reported that hawk moths are responsible for
most of the pollen exchange. Moths visit the flowers searching for nectar. Pollen is
transported on the moth’s tongue by large species and rarely on the body by smaller
species. Wind pollination has also been reported (Sritakae et al. 2011).
2.2.5 Parthenocarpy
Parthenocarpy in papaya is not a general rule but occurrences have been reported.
There are apparently some female trees that exhibit parthenocarpy. In an experiment,
FIGURE 2.2 (See colour insert.) Major floral visitors/pollinators of papaya.