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Comparative drought tolerance of tall and dwarf sunflowers

Connor, D.J. Prof; Ph: (03) 9344 5019; Fax: (03) 9344 4665;

Research organisation: University of Melbourne, Parkville Vic 3052

Collaborators: Comparative work on transpiration efficiency of sunflower cultivars is underway at the Research School of Biological Sciences ANU (Dr Farquhar). Field performance of sunflower in rainfed production in Queensland (Dr Hammer, Queensland DPI).

Sponsor: Oilseeds Research Council


To elucidate the relationship between stature, assimilate storage, yield and yield stability in the newly emerging dwarf sunflowers in comparison with earlier tall cultivars.


Pot and field experiments of the response of sunflower to transient stresses. Measurements of growth and yield and of the dynamics of labile carbon in the plant.


Transpiration of short hybrids before anthesis was less than that of taller hybrids. This was associated with their smaller interception of radiation.

Regulation of transpiration, irrespective of cultivar, depended upon timing of water shortage. Prior to anthesis the major effective was through reduced leaf expansion and after anthesis by a combination of stomatal response and leaf senescence.

Yield and radiation-use efficiency of dwarf hybrids was limited by their relative inability to set seed. This was identified by analyses of the partitioning of assimilate during grain filling. During this period dwarf cultivars have a smaller radiation-use efficiency than tall hybrids.

A simple two-parameter model of yield was developed that could explain yield response to biomass/transpiration and source sink relationships.

Period: starting date: 1988-07; completion date 1991-06

Status: terminated

Keywords: sunflower, drought stress, tall and dwarf hybrids


Sadras, V.O. and Connor, D.J. (1990). Sink-sink and source-sink interactions between stems and reproductive structures in sunflower with ontogeny and water stress. Proceedings of the 5th Australian Agronomy Conference, Perth, p.510.

Sadras, V.O., Connor, D.J. and Whitfield, D.M. (1990). Yield and yield components of sunflower hybrids of different stature under water stress as affected by source-sink relationships between stems and reproductive structures. Proceedings of the Australian Sunflower Association, 8th Workshop, Kooralbyn, pp. 98-102.

Sadras, V.O. and Connor, D.J. (1991). Physiological basis of the response of harvest index to the fraction of water transpired after anthesis. A simple model to estimate harvest index for determinate species. Field Crops Research 26, 227-239.

Sadras, V.O., Whitfield, D.M. and Connor, D.J. (1991). Regulation of evapotranspiration and its partitioning between transpiration and soil evaporation. A comparison between hybrids of different stature. Field Crops Research 28, 17-37.

Sadras, V.O., Whitfield, D.M. and Connor, D.J. (1991). Transpiration efficiency in crops of semi-dwarf and standard-height sunflower. Irrigation Science 12, 87-91.

Connor, D.J. and Sadras, V.O. (1992). Physiology of yield expression in sunflower. Field Crops Research 30, 333-389.

Sadras, V.O., Connor, D.J. and Whitfield, D.M. (1992). Yield, yield components and source-sink relationships in water-stressed sunflower. Field Crops Research 31, 27-39.


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