Seed Germination Physiology and Nursery Establishment of Croton macrostachyus Hocht. Ex Del.
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Date
2007-07
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Addis Ababa University
Abstract
Germination studies were conducted on seeds of Croton macrostachyus Hochst. ex Del. with a
view to analyzing effects of different seed pre-treatment procedures. Seed pretreatments were
achieved using various concentrations of gibberelic acid (GA3), potassium nitrate (KNO3),
various dilutions of plant-derived aqueous smoke extracts, and distilled water (control) under
illuminated (using fluorescent lamp = ca 40 μmol m-2 s-1) and non-illuminated ( buried in sand)
conditions. Studies on the germination responses of seeds sown in pots, provenance differences,
impact of seed storage time, as well as nursery establishment requirements for the seedlings
were also conducted. Experiments were conducted in Addis Ababa under laboratory, glasshouse,
and nursery conditions. The study found that percentage germination, mean germination time,
and germination vigor were best when seeds were pre-treated with aqueous smoke extracts and
were significantly different (P<0.001) from those pre-treated with either GA3 or KNO3. Of all
the pre-treatments employed, seeds under non-illuminated conditions resulted in significantly
higher (P<0.001) final germination percentage and vigor value than those allowed to germinate
under the light conditions. Final germination percentage and germination rate were significantly
(P<0.001) higher for seeds germinated in the glasshouse compared to those germinated outside
the glasshouse. Seed provenances from east Wollega, Ilubabor, and Jimma were similar in terms
of final germination percentage, mean germination time, and germination vigor, while these
were significantly (P<0.01) different from west Arsi (Shashamane) and west Shoa (Bako)
provenances. Germination percentage and vigor decreased with increasing storage time for all
storage temperatures. Also, mean germination time for seeds stored at room temperature (22° C)
significantly (P<0.01) increased compared to those stored at 15 and 5° C Growth media
containing red soil, decomposed cow dung and sand in ratios of 4:3:1, 4:1:3, 4:3:2, 2:1:1, and
1:1:1, respectively resulted in significantly (P< 0.05) better height growth compared to the
mixture containing red soil and decomposed cow dung in equal proportions. From these
investigations, it is concluded that pre-treating seeds of C. macrostachyus with aqueous smoke
extract is the best option for attaining maximum germination indexes. The results also indicate
that the species is easy to propagate by seed, seedlings grow fast and reach planting stage within
5-6 months if a soil mixture containing red soil, decomposed cow dung, and sand in equal
proportions is used for the nursery establishment under suitable growing conditions. But
germination conditions of the species vary from region to region and seeds are short-lived if
stored under room temperature.
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Biology