Physiological Disorders 127
sprays (0.1%) is more effective than soil application. The basal application of borax
at 5.0 g/plant at onset of reproductive stage is very effective to control the bumpy
fruit disorder of papaya, however, application of 13% borax at 12.5 kg ha−^1 or boron
at 1.63 kg/ha for sandy loam soils of North Bihar was also found effective (Saran
et al. 2013a, b, c, d). It is important to go for only one spray of boron at initial fruit
development stage and if both are combined, it may prove toxic to the plant. It is also
suggested to eliminate through pruning all the fruits before physiological ripening
that show bumpiness aspect and boron deficiency, because they do not have commer-
cial value due to bad appearance and low level of sweetness in its pulp.
11.2 Carpelloidy Fruits
Papaya plants in orchards, sometimes, fail to develop appropriate fruit shape
(Figure 11.2). The plant may begin to develop fruits, but they are deformed/warty.
Gynodioecious lines were the sensitivity of many hermaphrodite genotypes to fruit
deformity caused by stamen carpelloidy. This is a genetic proclivity affecting floral
development in hermaphrodites such that stamens become carpel-like and attach to
the ovary in irregular or occasionally symmetrical lobes particularly during the cool,
wet season. Carpel abortion is usually most pronounced under warm, dry season
(Manshardt 2012).
The hermaphrodite plants are sexually ambivalent, producing staminate, perfect
and pistillate flowers. The pistillate plant is stable. Staminate and hermaphrodite
plants may be phenotypically stable or ambivalent, going through seasonal sex-
reversal, during which they produce varying proportions of staminate, perfect and
pistillate flowers (Ram 1996). The female plants normally bear pistillate flowers, but
rarely, they can produce bisexual flowers. Alterations and reversions of bisexuality
have frequently occurred during angiosperm evolution and resulted in functional
unisexuality (male or female sterility) or morphological unisexuality (Mitchell and
Diggle 2005). Through these alterations, carpelloidy/pistilloidy, restricted to the
FIGURE 11.2 (See colour insert.) Carpelloid fruits of hermaphrodite papaya line, PS-3.