NUTRIENT STATUS, WATER-UPTAKE AND GAS-EXCHANGE FOR 3 DESERT SUCCULENTS INFECTED WITH MYCORRHIZAL FUNGI

Mycorrhizal infection and its consequences were assessed for Agave deserti Engelm., Ferocactus acanthodes (Lem.) Britton & Rose, and Opuntia ficus-indica (L) Miller. For A. deserti and F. acanthodes in the field, mycorrhizal infection varied from 2 to 11 %; the higher infection in May than in March 1991 was probably associated with improved soil water conditions. Using field-collected fungi, mycorrhizal infection for glasshouse-grown A. deserti, F. acanthodes and O. ficus-indica varied from 8 to 64 %, with the highest infection occurring for lateral roots of A. deserti. Five months after inoculation, root P was significantly higher (P < 0.01) for inoculated A. deserti and shoot P and Zn were significantly higher (P < 0.02) for inoculated A. deserti and F. acanthodes compared with uninoculated plants. Root hydraulic conductivity (L(p)) of lateral roots of A. deserti was 24 % higher for inoculated than for uninoculated plants (P < 0.1). The increase in L(p) was caused by a higher radial conductivity, which could be due to increased root cell membrane permeability and more hyphal entry points. Daily net CO2 uptake was 19 % higher for inoculated than uninoculated A. deserti. Mycorrhizal infection apparently enhances water and nutrient uptake in dry environments for these three desert succulents.