Date of Award

2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr-. Ali EI-Keblawy

Second Advisor

Dr. Turki Al-Turki

Third Advisor

Dr. Adam Aboubacar

Abstract

Cyperus conglomeratus is among few species that tolerate the instability of sand dunes and its low nutrients. This species tolerates grazing animals and sand burial. It is considered as a good fodder for both domestic and wildlife animals. It has the potential to fix sand dunes. In addition, a preliminary observation indicated the presence of high contents of oil in the seeds. Despite the ecological importance of C. conglomeratus, little information is available about germination behaviour and seed composition. The present study assessed the dormancy, germination requirement, tolerance to salinity and drought during germination stage, the impact of dormancy regulation chemicals on innate dormancy and salinity-induced germination inhibition and seed composition of the glycophytic desert sedge C. conglomeratus seeds.

Fresh seeds of C. conglomeratus have little innate dormancy; 84% of the seeds germinated in distilled water. In addition, none of studied dormancy regulating substances improved seed germination. The effects of maternal habitat, time of seed maturation and seed storage, and their interaction were assessed on light and temperature requirements during seed incubation on final germination percentage and germination rate of C. conglomeratus. The results showed significant effects for maternal habitat, time of seed collection, seed storage and both light and temperature of seed incubation and their interaction on both germination percentage and rate. Seeds of C. conglomeratus produced on dry sand dunes (AI Wathbah, Al Khattem and Dubai) produced higher germination percentages whereas those produced in the two sites of Al-Ain (Manaseer and Industrial area) produced significantly lower germination. The lowest germination was recorded for seeds of Liwa population and this was attributed to the extremely water stress in that area which would lead to improper seed filling and high rate of seed abortion.

Both light and temperature of incubation significantly affected the final germination percentage and germination speed of C. conglomeratus. Germination in light was significantly greater than it in dark, especially at higher temperature. Germination at higher temperatures was significantly greater than that at lower temperatures. The light requirement for germination of C. conglomerates seeds at higher ensures that they will germinate successfully on or near the soil surface when other conditions are suitable for seedling emergence. Such result might explain the high seedling emergence observed in disturbed sand dunes, especially after effective rainfall at the end of the rainy season.

The effect of salinity, light and temperature of incubation and their interaction had significant effects on final germination percentage of C. conglomeratus. The germination was greatly reduced in 25 mM NaCl and completely inhibited in 50 mM NaCl. Salinity tolerance was greatest in darkness at higher temperatures. For all salinities, no seeds were recovered at the lower temperatures and recovery germination percentage was significantly greater at 30/40 °C than 25/35 °C. Fusicoccin, GA3 and kinetin, completely alleviated salinity induced dormancy in all salinity levels. Nitrate and thiourea completely alleviated the germination inhibition in lower salinities, but partially alleviated it in 100 mM NaCl.

The effect of Polyethylene osmotic pressure on the germination of C. conglomeratus seeds was significant. The final germination was 90% in -0.1 MPa then decreased to 67%, 57% and 44% in -0.2, -0.3 and -0.4 MPa, respectively, and completely inhibited in -0.5 MPa This result indicates that the germination inhibition in saline solutions is more likely due to osmotic effect, rather than ion toxicity.

Final germination of fresh seeds of C. conglomeratus was significantly greater, compared to it for seeds stored for 15 months. This result indicates that storage either induced a secondary dormancy or resulted in viability loss of the seeds.

There was no compositional analysis data available for the seeds of this plant. Seeds collected from the plants in the sand dunes of Abu Dhabi, Dubai and Al-Ain were found to contain moisture- 2.51%, ash- 7.74%, fat- 29.5% and protein- 13 .5%. The seeds of this plant are rich in oil and the fatty acid profile of the soxhlet extracted fat was determined by capillary gas chromatography and found to be: C10:0- 0.10, C12:0- 0.10, C14:0 - 0.16, C16:0 -7.47, C16:1 - 0.12, C18:0 - 3.52, C18:1 -73.8, C18:2- 13.14, C18:3 - 0.56, C20:0 - 0.12, C20:1 - 0.27, C22:0 - 0.39, C22:1 - 0.17. Lipids were also extracted using supercritical fluid extraction (SFE) and SFE conditions of 50 °C and 400 bar gave maximum yield of 28.6%. The fatty acid profile of SFE oil was similar to that of the soxhlet extracted oil. The mineral composition (mg/kg) was found to be as: Na: 297, K: 3029, Ca: 896, Mg: 2303, Fe: 191, P: 3491, Cu: 9.57 and Zn: 53.3. Heavy metal contaminants (mg/kg)- Pb: 0.23, Cd: 0.14 were found to be within acceptable limits. The study indicates that the seeds are highly nutritious and the seed oil is rich in unsaturated fatty acids. The seeds could serve as a highly nutritious feed for animals and poultry.

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