|Title:||Acacia Abyssinica Hochst. Ex Benth: Pod and Seed Characteristics, Germination Physiology and Potentials for Seedling Establishment on Degraded Land|
|???metadata.dc.contributor.*???:||Dr. Legesse Negash|
|Publisher:||Addis Ababa University|
|Abstract:||This study was conducted on pod and seed characteristics, gennination physiology as well as the potentials of Acacia abyssinica Hochst. ex Benth ssp. abyssinica for growing on degraded land. Mature pods of A. abyssinica were collected from trees found in and around Addis Ababa (within a radius of 35 km). One hundred pods per tree were collected from 26 different trees. Comparison of the means of pod length, pod width and seed number per pod showed significant differences (p < 0. 05) among samples obtained from the different localities. Pod length, pod width and number of seeds per pod ranged between 3.7 and 14.4 cm, 1.0 and 2.7 cm and 2 and 13 respectively. There was no significant correlation behveen pod length and width. Pod length and number of seeds per pod were significantly correlated (p - 0.000). On the other hand, pod width and number of seeds per pod were negatively con•elated (p - 0. 000). Seeds collected from 35 different trees were made into 17 bulks (each containing 1000 seeds). the weight of the bulks ranged from 7 4. 01 to 116.11 g. There were significant differences (p - 0. 000) among the mean weights of the 17 seed bulks. Effects of gibberrelic acid (GA;/, indole-3-acectic acid (LAA) and kinetin with concentrations ranging from 103 M to 107 on percentage germination and radicle length of chemically scarified seeds of A. abyssinica were examined None of the plant growth regulators significantly increased the total percentage germination of seeds as compared to the control. Germination percentage decreased significantly at higher concentrations of LAA (103 M and107) and kinetin (103 M)LAA at 1 03M delayed germination for about a week as compared to the other concenhations of the same, though 63% of the seeds germinated within 10-15 days after incubation. GA3 (at 103 M) significantly increased radicle length, while LAA at 104M, 105 and 107M significantly decreased the radical length as compared to the control. The investigation on the potential of the species for growing on degraded land involved the growing of seedlings (GA3 104 M treated and the control) in plastic bags in the greenhouse. Soil samples from degraded land were collected from geomorphically different locations from an area ca 4 km2 along the road on the Modijo-Zeway road, at about 81 km south of Addis Ababa. Soil samples that served as a control were collected from places in and around Addis Ababa where A. abyssinica is currently found growing. Germinants from 104 M GA3 and the control were planted in both types of soils and were left to grow in the greenhouse for 12 weeks. All the seedlings survived until harvest. Chemical and physical analyses of the soil samples were conducted in the National Soils Laboratory in Addis Ababa. The results of the analyses indicate that total nitrogen organic carbon and available phosphorus were significantly higher (p < 0. 05) in the soils collected from places where A. abyssinica is curtly growing than those from the degraded land On the other hand pH, Na, K, Ca, and CEC were fo11nd significantly higher (p - 0.00) in the soils collected from degraded land The mean values of plant height, number of branches, number of leaves, shoot dry weight and root dry weight were found to be significantly higher in the controls. From the results, it could be concluded that: (I) the presence of hard seed coats is the most important factor inhibiting germination in seeds of A. abyssinica; (2) provided that seeds are carefully scarified (chemically or mechanically), no gennination stimulators are required for obtaining maximum percentage germination; and (3) the survival (until harvest} of the seedlings in soils collected Ji-om degraded land could indicate that A. abyssinica has the potentials for growing in degraded land provided that the minimum moisture requirements of the species is met.|
|Description:||A Thesis submitted in (partial) fulfillment for the Degree of Master of Science in Biology. Addis Ababa University|
|Appears in Collections:||Thesis - Biology|
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