Notes and Brief Articles 297In two other experiments, after subjecting apothecia to the initial z-day

darkness in a stream of saturated air, the rate of discharge withoutagitation was determined for 2 h, following which an apothecium in eachexperiment was vibrated continuously for 5 h and then allowed to remainstill. After the first 3 h of the 5 h period, the apothecium was illuminatedwith blue light for I h. The results (Fig. 7) indicate again no significantchange in rate on the onset of vibration, but a puff was obtained im­mediately on introducing blue light. In an earlier paper the action ofblue light in inducing puffing has been considered (Ingold & Oso, 1969).It is thus clear that the apothecia which failed to puff under condition ofvigorous agitation, were, in fact, in a condition to do so.

REFERENCES

BULLER, A. H. R. (1934). Researches onfungi, vol. VI. London: Longmans, Green and Co.INGOLD, C. T. (1965). Spore liberation. Oxford: Oxford University Press.INGOLD, C. T. & MARSHALL, B. (1953). Further observations on light and spore dis­

charge in certain Pyrenomycetes. Ann. Bot. 27, 481-491.INGOLD, C. T. & OSO, B. A. (1969). Light and spore discharge in Ascobolus. Ann. Bot. 33,

463-471.Oso, B. A. (1969). Spore discharge in discomycetes in relation to changes in relative

humidity. Trans. Br. mycol. Soc. 53, 119-126.

B. A. oso, Department ofBotany, Birkbeck College, London*

'GRAMoxONE' W: ITS EFFECTS ON SPORES AND MYCELIA

OF RHIZOPUS STOLONIFER

During investigations into the effects of herbicides on the growth ofsoil fungi, a commercial formulation of paraquat, 'Gramoxone' W, twasfound to affect the spores of Rhizopus stolonifer at concentrations as low as10 p.p.m. Spores used to inoculate Petri dishes of either Czapek-Dox agaror potato dextrose agar (PDA) containing 10 p.p.m. of paraquat failedto produce a mycelium. On untreated plates the spores germinated rapidlyand the resulting mycelium covered these plates within 48 h of inoculation.Further investigations revealed that the growth of mycelium from sporeswas sensitive to even lower concentrations of 'Gramoxone' W. Plates ofPDA incorporating' Gramoxone' W at five concentrations ranging fromo to 5 p.p.m. of paraquat, were inoculated with spores of R. stolonifer andincubated at 25 "C. Although spore germination was not prevented byI and 5 p.p.m. of paraquat, the subsequent rate of growth of the colonieswas reduced to 40 %of the growth rate of the controls.

By contrast, hyphal inocula of R. stolonifer were more tolerant of' Gram­oxone' W. Plates of PDA incorporating 'Gramoxone' W at concentra­tions of between 0 and 500 p.p.m. of paraquat were inoculated withhyphal disks (4 mm diam) cut from the margin of a colony growing on

'" Present address: Department of Botany, University of Ibadan, Nigeria.t Registered trade mark of Plant Protection Limited.

Trans. Br. mycol. Soc. 53 (2), (1969). Printed in Great Britain

298 Transactions British Mycological Society

PDA. The inoculum disks were inverted to bring the hyphae into directcontact with the medium. Colonies of R. stolonifir arising from hyphalinocula were unaffected by 10 p.p.m. of paraquat in the medium andgrowth continued, at a reduced rate, from inoculum disks on mediumincorporating 100 p.p.m. of paraquat.

There seemed to be two possible explanations for the greater sensitivityto paraquat of growth of mycelia from spore inocula compared withgrowth from hyphal inocula: (a) interference by paraquat with someparticular process of spore germination; (b) interference with substrateutilization (i.e. the mycelium growing from hyphal inocula might beexisting on nutrients present in the original disk, not those in the paraquat­containing agar).

Two more experiments were therefore carried out. In the first, 4'0 mmdisks of fungal hyphae on cellophane, instead of on agar, were used toinoculate plates containing 10 p.p.m. of paraquat. In the second, acoverslip supporting a 4'0 mm disk of PDA, inoculated with spores ofR. stolonifir, was placed on the surface of PDA containing 10 p.p.m. ofparaquat. The coverslip prevented the herbicide from diffusing into thedisk of 'plain' agar and inhibiting spore germination. Results were con­sistent with the suggestion that' Gramoxone' W interfered with substrateutilization. Growth of R. stolonifir from cellophane inocula on mediumincorporating paraquat was slow and it ceased before the myceliumreached the edge of the plate. The colonies on PDA containing 10 p.p.m.of paraquat which arose from spores inoculated on to a disk of' plain' agargrew at the same rate as the controls without paraquat.

Table I. Effects of ,Gramoxone' Won germination ofspores of R. stolonifer

Spores not Germ tube Germ tube> Germ tubeMedium germinating = bud spore diameter branching

Control 58 10 8 24ro p.p.m. 61 12 27 0

paraquat

However, 'Gramoxone' W was also shown to have some effect ongermination. Spores of R. stolonifer inoculated into liquid medium con­taining 10 p.p.m. of paraquat as 'Gramoxone' W were examined by lightmicroscopy. After 20 h incubation at 25° four stages of germination wererecognized: (I) no visible germination, (2) the appearance of a small bulgeor bud on the side of the spore, (3) the further development of this budinto an extending germ tube; and (4) branching of the germ tube. Detailsof the first 100 spores examined from the paraquat-containing mediumand from the controls are given in Table I. 'Gramoxone' W did not pre­vent germination of the fungal spores, but it induced germ tube deformi­ties. Distortions characteristic of' Gramoxone' W treatment are shown inFig. 1 A. By contrast, Fig. 1 B shows an untreated spore, incubated for thesame length of time, with a healthy branching germ tube.

Trans. Br. mycol. Soc. 53 (2), (1969). Printed in Great Britain

Notes and Brief Articles 299Rhizopus spp. occur commonly in soil. They grow rapidly by comparison

with other soil fungi and they are among the primary colonizers of organicmatter incorporated into soil. These results, indicating that low concentra­tions of ' Gramoxone' W might reduce the ability of spores of R. stoloniferto colonize a substrate containing residues of the herbicide, suggest that

A~

10p m

B

I-:-:--i10pm

Fig. 1, R. stolonifer. A, Spores germinating in liquid medium containing 10 p.p.m. ofparaquat as ' Gramoxone ' Wj B, a spore germinating in control medium (both 20 hafter inocula tion).

patterns of saprophytic colonization in the field may be affected by herbi­cides. The concentrations of ' Gramoxone' W used in these experimentsare well within the range likely to occur in sprayed vegetation in the field.

VALERIE WILKINSON and R. L. LUCAS, Department ofAgricultural Science, University of Oxford

ANAEROBIC GROWTH OF FUNGI

J. W. Foster (1949) said: ' One of the major metabolic differencesbetween fungi and bacteria is that there are no anaerobic moulds eitherobligate or facultative.' Anaerobic growth has, however, been achieved inrecent years with species of Mucor and Fusarium (Bartnicki-Garcia &Nickerson, 1962; Gunner & Alexander, 1964) and other fungi (Stotzky &Goos, 1965).

Trans. Br. mycol. Soc. 53 (2), (1969). Printed in Great Britain