WATER RELATIONS AND GAS EXCHANGE OF MYCORRHIZAL <em>LEUCAENA</em> <em>LEUCOCEPHALA</em> SEEDLINGS

Abstract

Leucaena leucocephala seedlings were inoculated with four species of vesicular-arbtiscular mycorrhizal (VAM) fungi, Gigaspora margarita, Glomus deserticola, Glomus etunicatum and Glomus intraradices, and two species of ectomycorrhizal fungi, Pisolithus tinctorius and Laccaria laccala. After 16 weeks in a glasshouse, plants inoculated with VAM fungi were significantly larger (biomass and leaf area) than non-inoculated control seedlings. Adequate VAM colonization was observed on root systems of plants inoculated with Gigaspora and Glomus species. Plants inoculated with ectomycorrhizal fungi were non-mycorrhizal but were larger in biomass than non inoculated control seedlings. Phosphorus concentration of mycorrhizal seedlings was significantly greater than nonmycorrhizal plants. Leaf water potential, leaf stomatal conductance and photosynthesis of seedlings were measured at mid-light during pre-, mid-, and post-water stress treatments. Although larger in biomass and leaf area, the VAM seedlings maintained slightly greater leaf water potential, leaf stomatal conductance and photosynthesis relative to the non-mycorrhizal plants at the peak of the drought. After re-watering the growth medium, leaf water potential, leaf conductance, and photosynthesis of the VAM seedlings were significantly greater compared to nonmycorrhizal plants. These data suggest that VAM fungi help leucaena leucocephala to avoid drought stress.