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Germination physiology
subjected to dark treatments were inspected every second day under a green “safe
light” with a PPFD of 0.3 mol m −2 s −1 . Mean germination time (MGT) was calculated
using the equation: MGT = (n×d)/N, where ‘n’ is the number of seeds germinated
on each day, ‘d’ is the number of days the experiment has been active and ‘N’ is the
total number of seeds germinated after 90 days (ELLIS & ROBERTS, 1981).
To test the effect of temperature and light on germination of four Romulea species,
decontaminated seeds were placed in growth chambers set at 10, 15, 20, 25, 30 and
30/15 C (day/night) with 16 h light: 8 h dark photoperiod. Petri dishes were covered
with aluminium foil for the dark treatment and were only opened under a ‘safe light’
as indicated earlier.
For the stratification experiment, surface decontaminated seeds were placed
between two layers of paper towelling moistened with distilled water. The towels
were placed inside a plastic bag and were covered with aluminium foil to eliminate
light. Seeds of all species were placed in a refrigerator at 5 C, except those of R.
rosea which were placed at 30 C, as EDDY & SMITH (1975) reported pre-chilling did
not improve the germination of this species. Seeds were kept under these conditions
for 7, 14 and 21 days before placing them for germination in a growth chamber set at
20 C. Control seeds did not receive stratification treatment and were placed in the
same growth chamber with the seeds of the 7 day stratified set.
For acid scarification, seeds were placed in 50% sulphuric acid for 5 min. Seeds
were also mechanically scarified by rubbing them between two pieces of sand paper
(P120 grade) for 1 min. Control seeds were not subjected to scarification treatment.
To test the effect of various plant growth promoting substances, seeds of R. rosea
were placed in Petri dishes with filter papers moistened separately with 10 -5 M of GA3,
Kinetin, KNO3, IBA, NAA and IAA. Smoke water concentration of 1:500 (v/v) and
butenolide (3-methyl-2H-furo[2,3-c]pyran-2-one) solution of 10 -8 M were also used in
this study. Butenolide is a compound isolated from plant-derived smoke water that
enhances germination of many seeds, including Eucomis (KULKARNI et al., 2006).
Plant-derived smoke water was prepared according to BAXTER et al. (1994) and
butenolide was isolated by the method of VAN STADEN et al. (2004). The effect of
macro-nutrient deficiency was investigated by placing seeds on filter paper
moistened with 3.5 ml of 50% Hoagland’s nutrient medium deficient of either nitrogen
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