This study was conducted on three naturally growing populations of the perennial grasses Panicum turgidum Forssk, Lasiurus scindicus Henrard and Pennisetum divisum Henrard in Egypt, south west Saudi Arabia and Qatar. Vegetative reproduction occurs by rhizome growth and sexual reproduction by tillering, where each tiller may end with a spike. The failure of sexual reproduction is mainly related to the extremely arid conditions and the overgrazing of flowering branches or seeds before dispersal. Phenological behaviour varied among species and differed within the same species in the three study areas. The earliness/lateness and narrow/wide spectrum of the active phenological phases (vegetative growth, flowering and fruiting) were species-dependent rather than locality-dependent. The phenophases of the three species in Saudi Arabia and Qatar proceeded at a faster rate than in Egypt. The plants collected from Saudi Arabia and Egypt attained higher energy content than those collected from Qatar. The overall energy content of P. turgidum (over 6 kcal. g -1 dry weight) is higher than that of L. scindicus and P. divisum (less than 6 kcal. g -1 dry weight). During the peak flowering/fruiting time, the fruits and rhizomes of the three species showed higher energy content than the roots and shoots. When the growth characteristics and energy content were taken as a measure of the grazing value, P. turgidum had better value as a forage plant than the other two species.
Abdel Rahman, A. A. (1986): The deserts of the Arabian Peninsula. pp. 29-54. In: Evenari, M., Noy-Meir, I., Goodall, D. W. (eds.), Ecosystems of the World 12B, Hot Deserts and Arid Shrublands. Elsevier Science Publishers B.V., Amsterdam.
Ecosystems of the World 12B, Hot Deserts and Arid Shrublands , () 29 -54 .
Draz, O. (1969): The hema system of range reserves in the Arabian Peninsula: its possibilities in range improvement and conservation projects in the Middle East. FAO.PL: PFC/13.11, Rome.
The hema system of range reserves in the Arabian Peninsula: its possibilities in range improvement and conservation projects in the Middle East. FAO.PL: PFC/13.11 , ().
Suliman, M. M. (1988): Dynamics of range plants and desertification monitoring in the Sudan. Desertification Control Bulletin, 16, 27-31.
'Dynamics of range plants and desertification monitoring in the Sudan ' () 16 Desertification Control Bulletin : 27 -31 .
Thomas, I. (1999): The recent history of rangelands in western Asia. Proceedings of VI International Rangeland Congress. Townsville, Australia. pp. 1048-1052.
'The recent history of rangelands in western Asia ' , , .
Wroblewski, R. J. (1977): Two methods of determining the caloric value of plant matter: a comparison. Poland Archive of Hydrobiology, 24, 299-303.
'Two methods of determining the caloric value of plant matter: a comparison ' () 24 Poland Archive of Hydrobiology : 299 -303 .
Zahran, M. A., Younes, H. A. (1990): Hema system: traditional conservation of plant life in Saudi Arabia. Science Journal of King Abdulaziz University, 2, 19-41.
'Hema system: traditional conservation of plant life in Saudi Arabia ' () 2 Science Journal of King Abdulaziz University : 19 -41 .
Hegazy, A. K. (2001): Reproductive diversity and survival of the potential annual Diplotaxis harra (Forssk.) Boiss. (Brassicaceae) in Egypt. Ecography, 24, (in press).
'Reproductive diversity and survival of the potential annual Diplotaxis harra (Forssk.) Boiss. (Brassicaceae) in Egypt ' () 24 Ecography .
Lieth, H. (ed.) (1974): Phenology and Seasonality Modeling (Ecological Studies, 8). Springer-Verlag, New York. 444 p.
Phenology and Seasonality Modeling (Ecological Studies, 8) , () 444 .
Hegazy, A. K. (2000): Intra-population variation in reproductive ecology and resource allocation of the rare biennial species Verbascum sinaiticum in Egypt. Journal of Arid Environments, 44, 185-196.
'Intra-population variation in reproductive ecology and resource allocation of the rare biennial species Verbascum sinaiticum in Egypt ' () 44 Journal of Arid Environments : 185 -196 .
Hegazy, A. K. (1996): Effects of cement-kiln dust pollution on the vegetation and seed bank species diversity in the eastern desert of Egypt. Environmental Conservation, 23, 249-258.
'Effects of cement-kiln dust pollution on the vegetation and seed bank species diversity in the eastern desert of Egypt ' () 23 Environmental Conservation : 249 -258 .
Hegazy, A. K. (1999): Deserts of the Middle East. pp. 360-364. In: Mares, M. A. (ed.), Encyclopedia of Deserts. University of Oklahoma Press, Norman.
Encyclopedia of Deserts , () 360 -364 .
Draz, O. (1979): Revival of hema system of range reserves as a basis for the Syrian range development programme. Proceedings of the First International Rangeland Congress. Denver, Colorado. pp. 100-103.
'Revival of hema system of range reserves as a basis for the Syrian range development programme ' , , .
El-Demerdash, M. A., Hegazy, A. K., Zilay, A. M. (1995): Vegetation-soil relationship in Tihamah coastal plains of Jazan region, Saudi Arabia. Journal of Arid Environments, 30, 161-174.
'Vegetation-soil relationship in Tihamah coastal plains of Jazan region, Saudi Arabia ' () 30 Journal of Arid Environments : 161 -174 .
Estabrook, G. F., Winsor, J. A., Stephenson, A. G., Howe, H. F. (1982): When are two phenological patterns different? Botanical Gazette, 143, 374-378.
'When are two phenological patterns different? ' () 143 Botanical Gazette : 374 -378 .
Evenari, M. (1981): Ecology of the Negev desert: a critical review of our knowledge. pp. 1-33. In: Shuval, H. (ed.), Development in Arid Zone Ecology and Environmental Quality. Balaban ISS, Philadelphia.
Development in Arid Zone Ecology and Environmental Quality , () 1 -33 .
Hegazy, A. K. (1995): Phytomonitoring and management of tar-piles on the Qatari coastal marshes, Arabian Gulf. Environmental Pollution, 90, 187-190.
'Phytomonitoring and management of tar-piles on the Qatari coastal marshes, Arabian Gulf ' () 90 Environmental Pollution : 187 -190 .
Hegazy, A. K., Eesa, N. M. (1991): On the ecology, insect seed-predation, and conservation of a rare and endemic plant species: Ebenus armitagei (Leguminosae). Conservation Biology, 5, 317-324.
'On the ecology, insect seed-predation, and conservation of a rare and endemic plant species: Ebenus armitagei (Leguminosae) ' () 5 Conservation Biology : 317 -324 .
Omar, S. A. S., Fargher, J., Andrew, M. H. (1999): Inventory of rangeland resources by soil survey techniques. Proceedings of the VI International Rangeland Congress. Townsville, Australia. pp. 782-783.
'Inventory of rangeland resources by soil survey techniques ' , , .
Orshan, G. (1986): The deserts of the Middle East. pp. 1-82. In: Evenari, M., Noy-Meir, I., Goodall, D. W. (eds.), Ecosystems of the World 12B, Hot Deserts and Arid Shrublands. Elsevier Science Publishers B.V., Amsterdam. 451 p.
Ecosystems of the World 12B, Hot Deserts and Arid Shrublands , () 1 -82 .
Pianka, E. R. (1983): Evolutionary Ecology. 3rd edn. Harper & Row Publications, New York. 416 p.
Evolutionary Ecology , () 416 .
Rathcke, B., Lacy, E. P. (1985): Phenological patterns of terrestrial plants. Annual Review of Ecology and Systematics, 16, 179-214.
'Phenological patterns of terrestrial plants ' () 16 Annual Review of Ecology and Systematics : 179 -214 .
Sestak, Z., Catsky, J., Jarvis, P. G. (eds.) (1971): Plant Photosynthetic Production Manual of Methods. Dr. W. Junk N. V. Publishers, The Hague, Netherlands. 818 p.
Plant Photosynthetic Production Manual of Methods , () 818 .
Snedecor, G. W., Cochran, W. G. (1967): Statistical Methods. 6th edn. Iowa State University Press, Iowa. 534 p.
Statistical Methods , () 534 .
Hoffman, A. J., Walker, M. J. (1980): Growth habits and phenology of drought-deciduous species in an altitudinal gradient. Canadian Journal of Botany, 58, 1789-1769.
'Growth habits and phenology of drought-deciduous species in an altitudinal gradient ' () 58 Canadian Journal of Botany : 1789 -1769 .
Larcher, W. (1980): Physiological Plant Ecology. 2nd edn. Springer-Verlag, New York. 303 p.
Physiological Plant Ecology , () 303 .
Le Houerou, H. N. (1986): The desert and arid zones of North Africa. pp. 101-147. In: Evenari, M., Noy-Meir, I., Goodall, D. W. (eds.), Ecosystems of the World 12B, Hot Deserts and Arid Shrublands. Elsevier Science Publishers B.V., Amsterdam. 451 p.
Ecosystems of the World 12B, Hot Deserts and Arid Shrublands , () 101 -147 .
Le Houerou, H. N. (1997): Biogeography of the arid steppeland north of the Sahara. pp. 207-228.
Biogeography of the arid steppeland north of the Sahara , () 207 -228 .
Lee, Y. N. (1971): Patterns of flowering in selected floras of the world. Journal of the Korean Research Institute for Better Living, 6, 1-52.
'Patterns of flowering in selected floras of the world ' () 6 Journal of the Korean Research Institute for Better Living : 1 -52 .
Ludwig, J. A., Reynolds, J. F., Whitson, P. D. (1975): Size-biomass relationship of several Chihuahuan desert shrubs. American Midland Naturalist, 94, 451-461.
'Size-biomass relationship of several Chihuahuan desert shrubs ' () 94 American Midland Naturalist : 451 -461 .
Migahid, A. M., El-Shourbagui, M. N. (1958a): The ecological amplitude of the desert fodder grass Panicum turgidum. III. Transplantation in Ras El-Hikma and Fuka. Bulletin de l'Institut de Desert d'Egypte, 8, 67-98.
'The ecological amplitude of the desert fodder grass Panicum turgidum ' () 8 III. Transplantation in Ras El-Hikma and Fuka. Bulletin de l'Institut de Desert d'Egypte : 67 -98 .
Migahid, A. M., El-Shourbagui, M. N. (1958b): The ecological amplitude of the desert fodder grass Panicum turgidum. IV. Comparison of the natural vegetation at Fuka and Almaza. Bulletin de l'Institut de Desert d'Egypte, 8, 99-108.
'The ecological amplitude of the desert fodder grass Panicum turgidum ' () 8 IV. Comparison of the natural vegetation at Fuka and Almaza. Bulletin de l'Institut de Desert d'Egypte : 99 -108 .
Hegazy, A. K., El-Demerdash, M. A., Hosni, H. A. (1998): Vegetation, species diversity and floristic relations along an altitudinal gradient in south-west Saudi Arabia. Journal of Arid Environments, 38, 3-13.
'Vegetation, species diversity and floristic relations along an altitudinal gradient in south-west Saudi Arabia ' () 38 Journal of Arid Environments : 3 -13 .
Hendricksen, R. E., Miller, C. P., Punter, L. D. (1999): Diet selection by cattle grazing tropical tallgrass pasture. Proceedings of the VI International Rangeland Congress. Townsville, Australia. pp. 222-223.
'Diet selection by cattle grazing tropical tallgrass pasture ' , , .