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Influence of Polyethylene Glycol-Induced Water Deficits on Tiller Production in Spring Wheat¹

Tillering of wheat (Triticum aestivum L.) is influenced by management practices and environment. Numerous studies have shown that final tiller number in wheat is reduced by drought. This study was conducted to determine the effect of decreasing osmotic potential in the root zone on the production of specific classes of tillers in spring wheat under controlled conditions. ‘Edwall’ and ‘Waverly’ were grown hydroponically in an environmental chamber. In addition to a control, water potential of the hydroponic medium was maintained at –0.1, –0.3 and –0.5 MPa with polyethylene glycol (PEG). Tiller production, leaf area, plant dry weight, and plant water relations were determined during vegetative development. Varying the osmotic concentration in the vicinity of the roots delayed tiller initiation and reduced leaf area production, dry matter accumulation, and the number of tertiary and quarternary tillers. The number of primary and secondary tillers was not affected by the PEG treatments. At 40 days after planting, the water and osmotic potentials of plants growing in the PEG treatments were more negative than the control plants, but the pressure potentials of the treated and control plants were similar. The plants acclimated to the PEG stress by accumulating solutes to lower their osmotic potential and maintain normal turgot. After acclimation, tiller initiation resumed but tillers were small. Thus, tiller initiation and emergence were less sensitive to osmotic stress than was the subsequent vegetative growth of the tillers.

Key Words: Triticum aestivum L. • Water stress • Tillering • Plant development

² Former graduate student, now postdoctoral fellow, CIMMYT, Apartado Postal 6-641, 06600 Mexico D.F., Mexico, and Associate professor, Dep. of Agronomy and Soils, Washington State Univ., Pullman, WA 99164-6420.

Received for publication September 6, 1986.