Tiller Development at the Coleoptilar Node in Winter Wheat 1

The formation of a secondary crown from a coleoptilar tiller can be important in wheat ( Triticum aestivum L.) producing regions where severe frosts can destroy or limit primary crown development in winter wheat. The outgrowth of a tiller from the coleoptilar node is influenced by both seed and environmental factors. This study was conducted to determine and compare factors likely to affect the carbohydrate status of the seedling, including seed reserves, seedling leaves, irradiance, and planting density. Plants of ‘Stephens’ wheat, grown from seeds of three sizes, were maintained in a controlled environment. Before being sown, endosperm reserves were removed; after germination, the blade from one of the first three foliage leaves was excised to determine the influence of reduced endosperm and foliage leaf food sources on coleoptilar tiller development. Plants grown from largest seeds produced the most coleoptilar tillers, and these tillers appeared earlier in leaf development. The greatest number of subtillers and nodal roots were formed on coleoptilar tillers when plants from large seeds were grown under bright irradiance and a lower planting density. Treatments where a reduced number of coleoptilar tillers was obtained included: small seed sizes, blade excision from the first foliage leaf, intermediate irradiance, and high planting density. No coleoptilar tillers or nodal roots were produced at coleoptilar nodes both when endosperm reserves were excised prior to germination and when seedlings were grown under low irradiance. The length of the coleoptilar tiller and the number of its leaves at termination of the experiment were influenced both by seed size and irradiance levels during seedling development. The use of large seeds and adequate irradiance levels during early seedling growth resulted in more numerous coleoptilar tillers with more vigorous growth.