(Ricinus communis L.) is cultivated around the world because of the
commercial importance of its oil.
Castor is extensively grown in Western India and in a few places around
the world. Brazil and China complement castor seed production. In
the recent years, the two countries have experienced a shift in the
crop pattern coupled with a steady increase in its domestic consumption.
Castor is grown under tropical conditions. It loves heat and humidity
and does best in regions where both are ample. India, gifted with
an ideal climatic condition, has recorded a produce of close to 850,000
tones of castor seed. This accounts for 75.6% of the world production.
Gujarat produces 86% of the total castor seeds in India followed by
Andhra Pradesh and Rajasthan. Mehsana and Banaskantha are the largest
castor producing districts in Gujarat.
In India, Castor is planted during July or August and harvested around
December or January. The seed pods are dried, de-podded and brought
to the market yards during December or January for trading. The Indian
variety of castor has an oil content of 48% and 42% can be extracted,
while the cake retains the rest.
Although commonly referred to as a "bean," castor is not a legume.
The plant has also been called the "castor oil plant." The Egyptians
used castor oil, one of the oldest commercial products, in lamps more
than 4,000 years ago, and seeds have been found in their ancient tombs
(Weiss 1971). Castor is considered by most authorities to be native
to tropical Africa, and may have originated in Abyssinia (Weiss 1971).
Although grown as annual plants, they act as perennials in the tropics
and subtropics and the plants reach heights of 9 to 12 metres. The
dwarf-internode cultivars 'Hale' and 'Lynn', and hybrids using them
as the pollen parent, vary in height from 0.9 to 1.5 m, compared to
1.8 to 3.7 m for the normal-internode types formerly grown (Brigham
1970a,b). Soil conditions, availability of moisture, and levels of
nutrients can cause considerable variation in height of plants. Plants
have a tap root, plus prominent lateral roots below the soil surface.
The large leaves are palmately lobed, (hence the name Palma Christi
used for castor) and are borne more or less alternately on the stems,
except for the two opposite leaves at the node just above the two
cotyledonary leaves. The petioles are usually several times as long
as the long axis of the leaves. The main stem is terminated by the
first or primary raceme, which often is the largest on the plant.
The primary raceme of early dwarf-internode cultivars usually occurs
after the 6th to 10th node. On later cultivars, the primary raceme
may occur after the 8th to 16th node. In introductions from other
countries, dwarf-internode types flowering after 40 or more nodes
After the first raceme appears, branches originate at the nodes below
it. The number of branches depends on plant spacing and in some cases
the cultivar. Under field conditions, two or three branches occur
at almost the same time, but generally in the following order: the
first branch at the node immediately beneath the primary raceme, the
second at the second node, and the third at the third node below the
primary raceme. The first racemes formed on the branches are commonly
called the "second set" of racemes. Subsequent branches arise from
the nodes just beneath the racemes of the second set. This sequence
of development continues as long as the plant remains alive and growing
actively. Thus, the development of racemes along any one axis is sequential,
making it possible for a plant to have racemes in all stages of development
from bud stage to complete maturity.
Typically, the racemes usually bear pistillate flowers on the upper
30 to 50% and staminate flowers on the lower 70 to 50% of the raceme.
Number of staminate and pistillate flowers can vary greatly, depending
upon raceme size. The flowers are without petals. After the pollen
is shed, the staminate flowers dry up and usually drop. The pollen,
which is discharged forcibly from the anthers, is carried to stigmas
mainly by wind (Brigham 1967). After fertilization, the pistillate
flowers develop into spiny capsules, though spineless types are known.
At maturity, the hull (pericarp) of the capsule may split along the
outside seam (dorsal suture) of each of the three capsule segments
(carpels). If splitting is violent, as in wild types, the seed will
be ejected and scattered on the ground around the plant. This type
of splitting (dehiscence) is not present in cultivars grown for mechanized
production. Seeds of present cultivars are held within the capsule
for several weeks after frost with no appreciable loss.
Seeds of current cultivars weigh from 3.0 to 3.5 g. Seed color ranges
from light to dark brown, with various mottling patterns. The seed
coat makes up about 25% of the weight of the seed. Oil content averages
50% on a dry weight basis.
Chromosome number of castor is 2n = 20. Autotetraploids have been
produced using colchicine, and haploids have been reported, but in
nature, castor is found mainly in the diploid form. There is little
or no loss of vigor when castor plants are inbred (Moshkin 1980).
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