| Yield per spike was significantly affected (P>=.01) by row spacing and
plant spacing (Table 1). Spikes in the low population
levels yielded more as compared to those in high population levels (Table
2). Initially there is a much greater ear potential than is normally
fulfilled, but this declines as crop growth and competition increases. At
the lowest population there is little evidence of competition until the
advanced stages of growth. At the higher populations the onset of competition
is earlier and potential declines more rapidly. Even as early as ear initiation
the ear potential is decreased quite substantially at the high populations
; this could not be because of a direct effect on ear development but because
competition has already reduced shoot size (WILLEY & HOLLIDAY 1971). It
has also been reported that gibberellic acid inhibits the development of
the barley spike (HUGHES et al. 1978), hence can be an important
factor in reducing grain yield at high plant densities. KIRBY & FARIS (1970)
suggests that levels of GA in the plant are affected by light intensity
or composition. Light could therefore be an important environmental factor
affecting both carbohydrate production and GA-regulated growth mechanisms
under the conditions of manipulated plant density. Acknowledgements The valuable assistance of Professor O. Tosun of Agronomy Department, University of Ankara, Turkey, is greatly acknowledged. Senior author is also grateful to the Government of Pakistan and Government of Turkey for providing financial assistance under cultural Programme. References CLEMENT, E.L. & F.C. COLLINS 1976. Arkansas Farm Res. 25: 5. FEJER, S.O., G. FEDAK & B.J. GILLESPIE 1979. Z. Pflanz. 83(2): 185-191. FRIEND, D.J.C. 1965. Can. J. Bot. 43: 345-353. HUGHES, W.G., J.J. BODDEN & S. GALANOPOULOU 1978. Annal. Appl. Biol. 88(2): 313-319. KASIMOV, I. 1976. Rasteniev'dni Nauki 13(3): 46-54. KIRBY, E.J.M. 1974. J. Agri. Sci. Camb. 82: 437-447. KIRBY, E.J.M. & D.G. FARIS 1970. J. Exp. Bot. 21: 789-798 LEAKY, R.R.B. 1971. J. Agrie. Sci. Camb. 77: 135-139. MADDENS, K. 1974. Revue de1' Agriculture 27(3) : 543-558. MANGLICMOT, J.M., G.M. GARCIA, N.S. TAYLAN & A.R. MADAMBA 1964. Philippine J. Pl. Indus. pp 151-158. NAZlR, S., M. RASHID, G. ALI, & M.A. GILL 1975. Pak. J. Agric. Sci. 12(3/4): 133-136. PUCKRIDGE, D.W. 1968. Aust. J. Agric. Res. 19: 191-201. PUCKRIDGE, D.W. & C.M. DONALD 1967. Aust. J. Agric. Res. 18: 193-211. STICKLER, F.C. 1961. Trans. Kansas Univ. Acad. Sci. 64(1): 1-6. WILLEY, R.W & R. HOLLIDAY 1971. J. Agric. Sci. 77: 453-461. |
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