Cultivation under partially controlled conditions with
artificial water stress, phenological monitoring and analysis
of floral morphology
In the plants grown in the greenhouse, the regular flower production began about 50 days after start of the cultivation. At thistime, three soil treatments were applied: moist soil—100% water-
holding capacity (WHC); soil with moderate drought stress—50%
WHC; and soil with severe drought stress—30% WHC. The water
retention capacity was determined with five substrate samples of
100 g, dried at 103 ◦C for 48 h for dry weight determination, after
saturated weight determination upon addition of water until the
percolated water volume was constant (Freire et al., 1980). Values
were adjusted to 30% and 50% WHC in the respective treatments.
The irrigation was controlled based on the gravimetric method
(Freire et al., 1980).
To check whether the treatments with water scarcity (soil with
50% and 30% WHC) induced water stress for the plants, a curve
was fitted to the data of water retention and the respective soil
water potential ( w). For this purpose, the water content in the
pots was measured monthly to monitor the water potentials the
plants were exposed to. By the end of the experiment, to check if
the water scarcity treatments imposed water stress, the rates of
net photosynthesis (A), transpiration (E) and stomatal conductance
(Gs) were evaluated. For this, a LiCor 6400 infrared gas analyzer
with fixed light source was used, whose value corresponds to the
optimal point of the species’ photosynthetic light response curve
(400 mol m−2 s−1).
The flowers and fruits of the different water treatments were
counted weekly. Seed production was estimated by multiplying
the number of fruits produced per plant by the respective aver-
age number of seeds. Seeds of 30 fruits were counted to estimate
the average number of seeds per plant and treatment. The flower
morphology parameters of the plants in each treatment (N = 30 per
treatment) were measured as described above.
The plant height (stem base to apex) was measured at the end
of the experiment, to check whether the vegetative growth of the
plants under water stress compared to those in moist soil was
reduced. From each value, the initial length of the cuttings was
subtracted. In addition to these measurements, the dry matter was
calculated by harvesting finally and drying the plants to constant
weight in an oven at 60 ◦C.