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Sunflower Germination under Simulated Drought Stress¹

Sunflower (Helianthus annuus L.) production is occurring and expanding undelr dryland conditions in many semiarid regions of the world. In some of these areas moisture stress may limit stand establishment. Germination of sunflower seeds in aqueous solutions of polyethylene glycol 20,000 (PEG) was evaluated as a screening technique for the selection of sunflower cultivars able to emerge under low soil moisture conditions. Germination of seed from four sunflower cultivars was determined at 0, –6, –11, –15, and –21 bars osmotic potential. No significant differences were observed among cultivars at 0 and –6 bars. Germination of three cultivars was significantly reduced at –11 bars. The germination of all cultivani was further reduced at –15 bars and completely inhibited at –21 bars. Emergence of the same cultivars from Palouse silt loam soil (fine-silty, mixed, mesic Pachic Ultic Haploxeroll) adjusted to –4, –6, –7, –11, and –14 bars matric potential was not significantly different at –4, –6, and –7 bars for three cultivars, while one cultivar exhibited reduced emergence at all these matric potentials. The emergence of the seed of all cultivars was reduced at –11 bars and completely inhibited at –14 Bars. Data from each analysis were pooled over all cultivars at each water potential for comparison of the two methods. Emergence from the soil was reduced at higher water potentials than germination in PEG solutions. However, the relationships of emergence to matric potential and germination to osmotic potential were similar indicating that PEG solutions may be useful in screening sunflower cultivars for improved emergence during moisture stress.

Key Words: Helianthus annuus L. • Polyethylene glycol • Emergence • Osmotic potential • Matric potential • Screening method

² Graduate research assistant, assistant professor of agronomy and former graduate research assistant, Washington State Univ., Pullman, WA 99164.

Received for publication May 6, 1982.