Volume 32, Issue 5
November 1950, pages 179-230
pp 179-204 November 1950
pp 205-214 November 1950
pp 215-221 November 1950
pp 222-226 November 1950
The opinion held by some that the baneful action ofStriga lutea on the host (maize) is entirely due to its depriving the host of its plant food is disputable.
In the culture experiment conducted with the young rice seedlings it appears that the death of the rice plant in the culture solution treated with the root extract ofStriga is due to some toxic substance contained in the extract. The effect ofStriga on rice in the field may thus be both parasitic and toxic.
From the culture experiment conducted with the young and aged rice seedlings, it is seen that the latter is able to resist the toxic effect much better than the former which perhaps partly explains why an early sown rice crop in the field is better able to resist an attack ofStriga than a late sown one.
An explanation for the differential behaviour between the young and old rice plants in contact withStriga root extract in the above culture experiment is suggested.
The mechanical injury done to the host plant by the haustorial hyphæ in the establishment of parasitism appears partly to contribute to the injury sustained by the rice plant on account of this parasite. This phenomenon appears to be not strictly in line with what has been observed in the case of the parasiteCuscuta in which the invading hypha fuses with the host vessel in such a way as not to cause it any mechanical injury and subsequent functional degeneration.
pp 227-230 November 1950
Cytological examination ofD. annulatum, D. caricosum, D. nodosum andB. intermedia was undertaken.
Meiotic and somatic chromosome numbers observed namelyn = 20 and2n = 40 inD. annulatum are in confirmation with the observations of the previous workers.
Meiotic and somatic chromosome numbers inD. caricosum have been observed as 20 and 40 respectively for the first time as the somatic number reported by Krishnaswamy (1939) does not agree with the number reported here.
The somatic chromosome number inD. nodosum is 2n = 40. This is being reported for the first time.
No polyploidy was observed in the forms of the three species ofDichanthium studied.
InB. intermedia 40 chromosome type is being reported for the first time and the existence of 60 chromosome type is confirmed.
The existence of polyploidy has been observed inB. intermedia and the increase in chromosome number is associated with the increase in size and other characters.