Classification of dormancy types

All species imbibed water within the first few hours. Methylene blue stain had passed through the seed coats of all species after 4 days. Embryo morphologies ranged from underdeveloped rudimentary types to those that were fully developed and non-endospermic (Table 21.1). Of the five Ericaceae tested, only one species, Leucopogon amplexicaulis (Rudge) R. Br., did not have an underdeveloped embryo. Only Petrophile pulchella (Schrad. and J.C. Wendl.) R. Br. seeds were germinated, with total germination reaching 100% at all three temperature regimes. Rates of germination, however, varied between the three temperature regimes (data not shown). The classes of dormancy identified were MPD and PD (Table 21.1).

The effect of fire cues on morphophysiological dormancy

Studies that applied fire treatments to fresh seeds identified 62 species from around Australia that were likely to have MPD. A total of 24 genera were represented from the families Antheriaceae, Apiaceae, Dasypogonaceae, Dilleniaceae, Ericaceae, Iridaceae, Ranunculaceae and Santalaceae. Of the 62 species identified, 96% failed to germinate with or without fire cue treatments or, occasionally, produced minimal (<5%) germination, at the end of 30 days.

Proportion of dormancy types in the shrub layer of the fire-prone Sydney flora

A total of 700 shrub species from fire-prone heath and forest communities within the Central Coast Botanical Subdivision were identified. Nearly half of these species were members of the Fabaceae, Proteaceae and Myrtaceae. A further one-third of all shrub species came from the Rutaceae, Ericaceae, Asteraceae and Lamiaceae families, all of which are known to have many species with a physiological component to their dormancy. Dormancy type was identified, or more confidently inferred, for 608 species. Of these, 28.6% were classified as ND and 71.4% as dormant. In terms of proportion of dormant species, the largest class of dormancy represented was PY (42.9%) followed by PD (40.1%) and MPD (17.1%) (Fig. 21.1). Since little information was available on germination requirements or dormancy type for most

Physical Physiological Morphophysiological Morphological dormancy (PY) dormancy (PD) dormancy (MPD) dormancy (MD)

Fig. 21.1. Shrub species from the Central Coast Botanical Subdivision (New South Wales) in south-eastern Australia in each dormancy class. Values are a proportion of total species (n = 434) known or inferred to be dormant (i.e. excluding species that are non-dormant or have unknown dormancy).

of the species identified, inferences were made, sometimes at a family level. For example, data from other fire-prone regions show that the majority of species in the Rutaceae have PD (Bell et al., 1993; Baskin and Baskin, 1998). Therefore, they were assigned to PD unless available research suggested otherwise. Most of the Sapindaceae and Rhamnaceae species were classified as PY using the same logic. Many Asteraceae species were left unknown due to the variability of dormancy types shown by species within this family. Although it is likely that species have either ND or PD, neither classification could confidently be assigned.

Was this article helpful?

0 0

Post a comment