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Sudan Journal of Agricultural Research
Effect of heat stress on subsequent germination and viability of Ischaemum afrum (J.F.Gmel.) Dandy seeds
Hamada A. A. , H. Abdalla, K. Werner, S. Joachim and K. Markus
Abstract:
Seeds of Ischaemum afrum were collected from fields in the Rahad Scheme;
Central Sudan and were stored for six months at 20 – 30 0C. These were
placed in Petri dishes, lined with filter paper, moistened with deionized
water and incubated at various temperatures for varying periods. Treatments
were replicated four times and germination recorded. Ungerminated seeds were
transferred to 30/20 0C (12/12 hrs light/dark) for 7 days and seed
germination recorded. The viability of ungerminated seeds was determined by
1% Triphenyltetrazolium chloride (TTC). The results indicated that exposing
unimbibed Ischaemum afrum seeds to 60 0C for 24 hrs had no adverse effect on
their germination and viability. However, both germination and viability
were reduced under moist conditions in the incubator or in the water bath at
45-60 0C. At these temperatures, it was observed that the higher the
temperature and/or the longer the exposure period, the greater were the
reductions in seed viability. Viability of seeds without glumes followed the
same trend but was apparently more sensitive to heat stress compared to
seeds with glumes. Indisciminately, 7 days of heat stress at 50 0C under
moist conditions killed all the seeds. At 55 and 60 0C, exposure period
required to reduce viability of glumed seeds by 90% was 24 hrs and 6 hrs,
respectively. Seeds that were previously imbibed at 30 0C were more
susceptible to a 60 min exposure at 60 0C in a water bath than previously
unimbibed ones. A 60 min exposure at 60 0C in a water bath had no adverse
effect on seed viability. In contrast, the reduction in viability amounted
to 70% following 20 min exposure periods made daily for 3 consecutive days.
The first indication of seed damage by heat stress was a delay in
germination. The results are briefly discussed in relation to solarization.
Sudan Journal of Agricultural Research Vol. 11 (2008) PP. 1-8
