ECOLOGY OF ASCLEPIAD LIANES 
105 
Marsdenia Rhyncharrhena 
16/14°C 25/15°C 16/14°C 25/15°C 
Shoot length (mm) 
Dry weight (g) 
66 
436 
199 
1142 
Shoot 
0.14 
1.57 
0.15 
1.58 
Root 
0.29 
1.89 
0.38 
0.71 
Total 
0.43 
3.46 
0.53 
2.29 
Table 2. Mean shoot length and dry weight of 18 wk old Marsdenia australis and Rhyncharrhena linearis 
seedlings at two temperature regimes. 
for supported young plants except for a single 
Marsdenia plant which twined 1.1 m up a stake 
in 10 weeks. Possible effects on growth caused by 
provision of support need investigating. 
PHENOLOGY 
Methods 
General observations were made at all sites. At 
site 1, from 13 February to 23 May 1990, effects 
of water supply on shoot growth and flowering 
were studied by watering two Marsdenia and 
three Rhyncharrhena plants with a total of 600 L 
per plant via 22 L containers feeding a dripper 
system running at 400 mL/hr. Watering stopped 
f SeVen " Week “°l d see dl‘ n g s °f Marsdenia aus- 
a ls (left) and Rhyncharrhena linearis (right) grown 
in a growth cabinet at 25/15°C. 
in May when rainfall had clearly provided avail¬ 
able water in the topsoil. Six unwatered control 
plants were monitored per species. 
At site 2, from 19 February to 6 April 1990, 
one Marsdenia and three Rhyncharrhena were 
given 150 L of water each. One Marsdenia and 
three Rhyncharrhena were monitored as 
unwatered controls. 
All plants monitored at sites 1 and 2 were 
more than 0.8 m high and were supported by 
shrub canopies. From 2 to 6 shoots per plant 
were tagged initially. Shoots were monitored 
until September 1990. Unfortunately it was log- 
istically impossible to provide continuous 
watering to a larger number of plants. This fac¬ 
tor, plus death of and damage to some shoots, 
produced very low replication in some cases, 
reducing the value of the experiment. Only a 
summary' of the results is given below. 
Results 
Flowering and fruiting. Observations in the Red 
Cliffs district on similar numbers of plants of 
each species from 1981 to 1990 gave a flowering 
time range of October to March for Marsdenia 
and February' to May for Rhyncharrhena. For 
the latter, however, buds can sometimes be seen 
even in July and September and we think it 
likely that flowering can occur from October to 
May (see also Cunningham et al. 1981, Jones & 
Gray 1988). In general, flowering for both occurs 
in the warmer months, especially when signifi¬ 
cant rain has fallen previously. However, Mars¬ 
denia is more likely to exhibit plentiful general 
flowering in December-January under a wide 
range of rainfall regimes. Rhyncharrhena seems 
to have a less definite flowering period; it seems 
more opportunistic, reacting more quickly with 
vigorous growth and flowering after significant 
summer-autumn rains. This species difference 
is dealt with more fully below. The smallest 
plants of both species seen flowering were about 
600 mm high. 
