Pollen size is one of the important characteristics to be used in evolutionary studies. Twenty-nine distinct collections of Coix, including both Coix aquatica (2n=10) and C. lacryma-jobi (2n=20), collected from different geographical regions of the Indian sub-continent, were taken for the present study. All the populations of Coix were field grown in two different climatic zones of India: (i) IGAU, Raipur and (ii) IARI, New Delhi.

In general, the pollen grains of Coix were round or oval in shape with a single pore. Although Coix aquatica has a lower chromosome number than C. lacryma-jobi, the mean pollen grain size of C. aquatica (87.26 and 60.00 µm) was found to be more than that of C. lacryma-jobi (63.05 and 35.83 µm) at IGAU, Raipur and IARI, New Delhi, respectively (Table 1.). Significant reduction in pollen size has been observed in all the populations of Coix studied. Various sized pollen grains have been recorded within and between different collections of both species of Coix studied.

Table 1. Pollen grain size (in µm) in Coix.
 

	Mean pollen grain size
Collection	At IGAU	At IARI
(A) Coix aquatica (2n=10)
Coix-20	105.00	68.00
Coix-24	69.00	54.00
Coix-25	93.00	65.00
Coix-27	73.50	49.00
Coix-28	67.50	46.00
Coix-29	72.00	48.00
Coix-30	75.00	46.00
Coix-36	96.00	64.00
Coix-44	114.00	70.00
Coix-48	105.00	68.00
Coix-55	87.00	58.00
Coix-56	102.00	68.00
Coix-57	105.00	75.00
Coix-59	82.50	61.00
Coix-62	75.00	50.00
Coix-63	90.00	60.00
Coix-64	90.00	65.00
Coix-65	82.50	58.00
Coix-66	90.00	62.00
Coix-67	90.00	60.00
Coix-68	75.00	50.00
Coix-70	90.00	70.00
Coix-71	78.00	65.00
MEAN	87.26	60.00

(B) Coix lacryma-jobi (2n=20)

Coix-50	51.00	38.00
Coix-51	63.00	39.00
Coix-52	67.50	40.00
Coix-53	64.80	46.00
Coix-54	72.00	50.00
Coix-60	60.00	40.00
MEAN	63.03	35.83

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