Journal of the Royal Society of Western Australia, 87(3), September 2004 
Australian Banksia species (Cowling & Lamont 1987). 
Once germinated, seeds were transferred to shallow 
seedling trays containing washed, coarse white sand in a 
temperature controlled glasshouse. In January 2001, 80 
seedlings per species were transferred into square pots 
18 cm tall by 8 cm wide, each containing coarse white 
sand with a top layer of small stones. Flooding trials 
began on 27 April 2001 and concluded 104 days later. 
Flooding was achieved using three 60 L clear plastic 
tubs each containing 10 pots per species. Tubs were filled 
with tap water until the pot, but not the seedling, was 
completely emersed. Another three tubs, set up exactly 
the same except with drainage holes, were watered twice 
a week for the duration of the flooding trial, and used as 
controls. Every two weeks seedlings were removed and 
all the tubs drained and scrubbed with tap water to 
remove the build up of algae on the tub walls. Seedlings 
were then put back into the tubs and refilled with fresh 
tap water. Four seedlings per species were removed from 
the tubs to assess the species' ability to recover after 36 
days of flooding. 
To examine the effects of submergence, 5-10 seedlings 
per species were placed in a 90 L clear plastic tub. This 
was filled with tap water until all plants were completely 
submerged. This tub was cleaned and refilled with fresh 
tap water every two weeks. Physiological data (stomatal 
conductance, chlorophyll fluorescence) were not collected 
from submerged plants because the leaves were 
constantly under water. 
Stomatal conductance 
Stomatal conductance and chlorophyll fluorescence 
data were measured approximately every 2 weeks from 4 
plants per species and treatment. Midday stomatal 
conductance (g s ) was measured on recently formed, fully- 
expanded leaves using a portable infra-red gas analyser 
(LCi, ADC Bioscientific Ltd, Hoddesdon, England) 
attached to a leaf chamber. Measurements were taken on 
relatively cloud-free, sunny days, with data collected 
within 1 min of enclosing the leaf. Conductance data 
were collected at ambient humidity and C0 2 
concentrations and when light intensity (PAR) was 
greater than 1000 pmol m' 2 s 1 . Day time air temperature 
within the glasshouse varied from 23-25°C. 
Chlorophyll fluorescence 
Chlorophyll fluorescence was measured on attached 
leaves using a modulated chlorophyll fluorometer (OS1- 
FL, Opti-Sciences, Tyngsboro, Massachusetts, USA). 
Midday measurements of potential photochemical 
efficiency of Photosystem II (F v /F m ) were recorded after a 
leaf dark adaptation time of 30 min using leaf clips 
provided by the fluorometer manufacturer. A reduction 
in the F v /F m ratio commonly indicates the occurrence of 
photoinhibition, particularly in plants exposed to periods 
of stress (Maxwell & Johnson 2000). Measurements were 
recorded from 4 plants per species and treatment. 
Actual efficiency of Photosystem II photochemistry, or 
quantum yield (^pg,,), was measured under natural light 
conditions on light-exposed leaves, using an additional 
light pulse during the midday period. O p , was 
calculated by the instrument according to Genty et al. 
(1989). was collected at PAR light intensity > 1000 
pmol nr 2 s* 1 and is used as an indication of overall 
photosynthetic performance (Maxwell & Johnson 2000). 
Seedling growth 
Four seedlings per species and treatment were 
harvested at the beginning of the experiment (27 April 
2001), towards the end (4 July) and at the end (7 August, 
B. littoralis only). Each seedling was separated into leaf, 
shoot (stem and side branches) and root components and 
Number of days 
Figure 1. Relative total (closed square), shoot (diamond) and root (open square) dry weight of Banksia seedlings subjected to continuous 
flooding. Data are means of four replicates and relative to data obtained for well-watered (control) seedlings. Dashed line (at 1) 
indicates where flood and control data would be equal. Asterisk indicates significant differences (P<0.05) between flooded and well- 
watered seedlings. SE bars are not included because of their overlapping nature. 
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