Deuterium Content in Organic Material of Hosts and Their Parasites
405
The average oD of the Australian hosts (all C3 plants) is -72.8%0 (±
19.55), and oftheir mistletoes, -51.1%0 (± 16.78). The difference (mistletoes
richer in deuterium) is highly significant (p < 0.001). In the African host
plants, the average oD values of the C3 plants is -67.8 (± 10.68) and -53.3
(± 12.31) for their parasites. In the CAM hosts from Africa, the average oD
value is -41.7 (± 21.36), and -54.4%0 (± 28.06) in their mistletoes. This
means that the ratio mistletoe/host is reversed in the pairs with CAM hosts,
compared with those with C3 hosts.
There is no correlation between the 013C values and the oD values of the
Australian (K = 0.160) or African hosts (K = 0.382) nor between the 013C
values and the oD values of the Australian (K = 0.259) or African parasites
(K = 0.073).
19.2.4 Isotope Contents of Parasitic or Saprophytic Fungi
and Their Host Plants
The last combination we analyzed for isotope relationships was woody
plants and associated wood parasites or saprophytes. In addition, a smut
(order Ustilaginales), the common corn smut, Ustilago maydis, which infects
maize plants and causes large boils or tumors, was included. In our experiment, the fungal spores were compared with the distorted leaves of the host
plant.
When we consider the isotope contents of the host plants and in fungal
fruiting bodies (basidiocarps) (Table 19.4), we come to the following conclusions:
The average Ol3C value of the eight hosts was -25.3%0 (± 2.26), and
-24.3%0 (± 1.31) of the fungi. The difference is not statistically relevant.
The average of the host oD values is -106.7%0 (± 16.16) and -50.9 (±
15.95) for the parasites. This difference is statistically highly significant
(p < 0.001).
We find a similar situation in the Zea mays/Ustilago may dis combination:
while the 013C values are identical (C4-typical), the relative deuterium
content of the fungal spores is much higher (oD considerably less negative)
than in the host tissue.
There is no correlation between the 013C and the oD values of the host
(substrate) or between the 013C and oD values of the fungi.
19.3 What Are the Reasons for the Isotope Discriminations?
The causes for differences in the 013C values between hosts and parasites (as
far as they exist) are in general more easily explained than the differences in
oD values.
405
The average oD of the Australian hosts (all C3 plants) is -72.8%0 (±
19.55), and oftheir mistletoes, -51.1%0 (± 16.78). The difference (mistletoes
richer in deuterium) is highly significant (p < 0.001). In the African host
plants, the average oD values of the C3 plants is -67.8 (± 10.68) and -53.3
(± 12.31) for their parasites. In the CAM hosts from Africa, the average oD
value is -41.7 (± 21.36), and -54.4%0 (± 28.06) in their mistletoes. This
means that the ratio mistletoe/host is reversed in the pairs with CAM hosts,
compared with those with C3 hosts.
There is no correlation between the 013C values and the oD values of the
Australian (K = 0.160) or African hosts (K = 0.382) nor between the 013C
values and the oD values of the Australian (K = 0.259) or African parasites
(K = 0.073).
19.2.4 Isotope Contents of Parasitic or Saprophytic Fungi
and Their Host Plants
The last combination we analyzed for isotope relationships was woody
plants and associated wood parasites or saprophytes. In addition, a smut
(order Ustilaginales), the common corn smut, Ustilago maydis, which infects
maize plants and causes large boils or tumors, was included. In our experiment, the fungal spores were compared with the distorted leaves of the host
plant.
When we consider the isotope contents of the host plants and in fungal
fruiting bodies (basidiocarps) (Table 19.4), we come to the following conclusions:
The average Ol3C value of the eight hosts was -25.3%0 (± 2.26), and
-24.3%0 (± 1.31) of the fungi. The difference is not statistically relevant.
The average of the host oD values is -106.7%0 (± 16.16) and -50.9 (±
15.95) for the parasites. This difference is statistically highly significant
(p < 0.001).
We find a similar situation in the Zea mays/Ustilago may dis combination:
while the 013C values are identical (C4-typical), the relative deuterium
content of the fungal spores is much higher (oD considerably less negative)
than in the host tissue.
There is no correlation between the 013C and the oD values of the host
(substrate) or between the 013C and oD values of the fungi.
19.3 What Are the Reasons for the Isotope Discriminations?
The causes for differences in the 013C values between hosts and parasites (as
far as they exist) are in general more easily explained than the differences in
oD values.