© 2006 Heron Publishing—Victoria, Canada
Physiology and anatomy of lenticel-like structures on leaves of Eucalyptus nitens and Eucalyptus globulus seedlings
Elizabeth Pinkard (1, 2, 5), Warwick Gill (3) and Caroline Mohammed (1, 2, 4)
1. Cooperative Research Centre for Forestry, Private Bag 12, Hobart, Tasmania 7001, Australia / 2. School of Agricultural Science, University of Tasmania, Private Bag 54, Sandy Bay, Tasmania 7005, Australia / 3. Tasmanian Institute of Agricultural Research, University of Tasmania, 13 St. Johns Avenue, New Town, Tasmania 7008, Australia / 4. ENSIS, CSIRO, Private Bag 12, Hobart, Tasmania 7001, Australia / 5. Corresponding author (Libby.Pinkard@ffp.csiro.au) / Received October 12, 2005; accepted November 11, 2005; published online May 1, 2006
Summary
Intumescences or abnormal, non-pathogenic, blister-like protuberant growths, form on Eucalyptus globulus Labill. and, to a much lesser extent, Eucalyptus nitens (Deane and Maiden) Maiden leaves when plants are grown in a high relative humidity environment. We examined the histology
of intumescences and their effects on leaf photosynthetic processes. Intumescences were induced by placing E. globulus and E. nitens seedlings in a relative humidity of 80% in a greenhouse for 5 days. Symptomatic and asymptomatic leaves of plants with intumescence
development were compared with leaves of control plants. Light-saturated carbon dioxide (CO2) assimilation (Amax) and responses of CO2 assimilation (A) to varying intercellular CO2 partial pressure (Ci) were measured. Symptomatic and asymptomatic leaf samples were fixed and sectioned and cellular structure was examined. Intumescences
greatly reduced the photosynthetic capacity of E. globulus leaves and were associated with reduced electron transport rate and ribulose bisphosphate (RuBP) regeneration capacity. Tissue
necrotization and cellular collapse of the palisade mesophyll and deposition of phenolic compounds in the affected areas,
probably reduced light penetration to photosynthesizing cells as well as reducing the amount of photosynthesizing tissue.
Photosynthetic capacity of E. nitens was unaffected. The intumescences resembled simple lenticels, both morphologically and developmentally. To our knowledge,
this is the first time that lenticel-like structures developed in response to environmental conditions have been described
on leaves.
Keywords:
CO2 assimilation, electron transport, histology, intumescence, oedema, RuBP.
