Inoculation with arbuscular mycorrhizal fungi enhances growth of Litchi
chinensis Sonn. trees after propagation by air-layering
Lychee (Litchi chinensis Sonn.) is typically propagated by air-layering
mature tree branches which are potted in fertilized, soil-free media after
cutting. The size of these branches, low phosphorus retention by pot
substrates, and fertilization all might combine to preclude benefits of
arbuscular mycorrhizas to lychee.
In order to examine the potential of
lychee to benefit from arbuscular mycorrhizas in an agriculturally
realistic context, lychee air-layers were grown for 469 days in ca. 95-1
pots of soil-free substrate
inoculated with field-collected arbuscular mycorrhizal roots or not at
two different levels of phosphorus fertilization.
fertilization (a one-time addition of ca. 1.32g 1-1 slow-release
triple-superphosphate) had no detectable effects on mycorrhiza formation,
lychee survival, net CO2 assimilation, or growth. Inoculation with
indigenous South Florida arbuscular mycorrhizal fungi improved leaflet
expansion as early as 120 after inoculation, and subsequently enhanced
height growth and leaf production but did not affect stem diameter
growth, net CO2 assimilation, or survival.
At harvest, although
mycorrhizal colonization was low (average 7.4% colonized root length),
mycorrhizal plants had 39% higher above-ground dry weight than control
plants. Below-ground dry weights did not differ, but innoculated plants
had lower fine root to dry leaf weight ratios than control plants.
Leaflets of inoculated plants had higher concentrations of P, K, Cu, and
Zn, and lower concentrations of Ca, Mg, and Mn than those of control
plants, but total Kjeldahl nitrogen and iron concentrations did not
differ significantly 10 months after inoculation. Mycorrhiza enhancement
of lychee growth occurred even though phosphorus clearly was not limiting
Our observations suggest that in this soil-free medium,
arbuscular mycorrhizal fungus enhancement of copper and iron nutrition
improved lychee growth.
David P. Janos1,3, Michelle S. Schroeder1,
Bruce Schaffer2 & Jonathan H. Crane2
1Department of Biology, University of Miami, P.O. Box 249118, Coral Gables, FL 33124-0421
2Tropical Research and Education Center, University of Florida, 18905 S.W. 280 Street, Homestead, FL 33031-3314
Received on 23 August 2000, Accepted in revised form 13 February 2001