A classification of the eucalypts

ABSTRACT Pryor, L.D., and Johnson, L.A.S. (Dept. Bot., Aust. Nat. Univ., Canberra, and Roy. Bot. Gardens and Nat. Herb., Sydney). A CLASSIFICATION OF THE EUCALYPTS (Dept. Bot. Puhl.), 102 pp., 1971.-­A new classification is presented of all taxa of EuaaZyptus (and Angophora) (Myrtaceae­Leptospermoideae), on the basis of studies from many disciplines and extensive field experience. This is not in the traditional revisionary form and formal nomenclatural innovations at the species and subspecies level will follow later. Infrageneric classification into subgenera, sections, series, and subseries follows a rationalised plan explicitly divorced from the traditional system embodied in the International Code of Botanical Nomenclature. This is accompanied by an equivalent and flexible system using 1- to 6-letter coded designations for taxa of the various ranks, which embodies the whole classificatory structure. There is a comprehensive index to specific and infraspecific names. Discussion covers the kinds of evidence used, the inflorescence, the operculum, the ovule, and the seed, as well as genetic behaviour, the range of variation-patterns found, and the case for recognition of segregate genera. Recognition of two (only) such genera (EuaaZyptus s. str. and Symphyomyrtus) as proposed by some recent authors is considered oversimplified and contrary to the evidence. Although division into a number of genera may perhaps be desirable in the future, it seems best at present to consider all the eucalypts as constituting a single genus with eight subgenera. Angophora would logically be included as one of these but, to avoid possible future reversals, its generic status ·is not· formally reduced at this· stage

Stomatal responses of Eucalyptus species to elevated CO2 concentration and drought stress

Five species of Eucalyptus (E. grandis, E. urophylla, E. camaldulensis, E. torelliana, and E. phaeotrica), among the ten species most commonly used in large scale plantations, were selected for studies on the effects of elevated CO2 concentration [CO2] and drought stress on stomatal responses of 2.5-month old seedlings. The first three species belong to the subgenus Smphyomyrtus, whereas the fourth species belongs to the subgenus Corymbia and E. phaeotrica is from the subgenus Monocalyptus. Seedlings were grown in four pairs of open-top chambers, arranged to have 2 plants of each species in each chamber, with four replications in each of two CO2 concentrations: 350 ± 30 mumol mol-1 and 700 ± 30 mumol mol-1. After 100 days in the chambers, a series of gas exchange measurements were made. Half the plants in each chamber, one plant per species per chamber, were drought-stressed by withholding irrigation, while the remaining plants continued to be watered daily. Drought stress decreased stomatal conductance, photosynthesis and transpiration rates in all the species. The effect of drought stress on stomatal closure was similar in both [CO2]. The positive effects of elevated [CO2] on photosynthesis and water use efficiency were maintained longer during the stress period than under well-watered conditions. The photosynthetic rate of E. phaeotrica was higher even in the fourth day of the drought stress. Drought stress increased photoinhibition of photosynthesis, as measured by chlorophyll fluorescence, which varied among the species, as well as in relation to [CO2]. The results are in agreement with observed differences in stomatal responses between some eucalyptus species of the subgenera Symphyomyrtus and Monocalyptus