The connection between the two vascular systems in the glume cushion provides a double supply source to the lower female glumes. The tunicate inhibitor gene, which appears to be on chromosome 6 (Mangelsdorf, 1958), acts by greatly reducing development of the outer system and lacks outer-inner connections. The consequence is that in the presence of the Ti (tunicate inhibitor) gene, the usual elongate growth of tunicate glumes (Tu on chromosome 4) as well as papyrescent glumes (Pn on chromosome 7) is stunted by starvation into about the length of normal glumes. In their modified expressions, the tunicate glumes still have their usual foliaceous texture but of normal (non-tunicate) length, while likewise the papyrescent glumes have their usual papery texture but of normal (nonpapyrescent) length. In normal maize (tu, pn), the Ti gene inhibits cupule development and in some backgrounds may result in a non-cupulate female rachis in either maize or teosinte. Non-cupulate teosinte has no fruit cases to protect its kernels.
Walton C. Galinat
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