Comparative Study of the Effect of Stress by the Heavy Metals Cd~(+2), Pb~(+2), and Zn~(+2) on Morphological Characteristics of Saprolegnia delica Coker and Dictyuchus carpophorus Zopf.

摘要

The effects of essential (Zn~(+2)) and non-essential (Cd~(+2) and Pb~(+2)) heavy metals on morphogenesis of two represantatives of informal group zoosporic fungi namely; Saprolegnia delica Coker and Dictyuchus carpophorus Zopf. were studied. These twospecies varied in their tolerance of each amended heavy metal. Lead had the most potent effect amongst the tested heavy metals in inhibiting the radial extension of the vegetative hyphae of the two tested species. The vegetative hyphae of S. delica andD. carpophorus assumed different morphological alterations compared with that at controls depending upon the applied heavy metal and the dose concentration. Both zoosporangial formation and discharges of the two tested fungi were greatly inhibited even at the low concentrations of Cd. Zoosporangia of D. carpophorus appeared curved at high concentrations of Cd. Zoosporangial formation and discharge of the two zoosporic fungi showed variable deformation when treated with Pb. The different applications ofZn nearly stimulated sporangial elongation in both zoosporic fungi. Sex organs varied in their numbers and morphogenesis at each treatment of the applied heavy metal. The gemmae of S. delica were greatly reduced or missed at the elevated toxic levels ofCd whereas they enhanced in numbers and size at most Pb treatments and little affected at Zn applications.