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Development and Growth Regulation

Development of the alt Mutant of Pisum sativum L. ¹

Department of Horticulture, Oregon State University, Corvallis, Oregon 97331, Department of Zoology, Oregon State University, Corvallis, Oregon 97331, National Clonal Germplasm Repository, Oregon State University, Corvallis, Oregon 97331, United States Department of Agriculture, Agricultural Research Service Horticultural Crops Research Laboratory, Oregon State University, Corvallis, Oregon 97331

The alt (albina-terminalis) mutant of Pisum sativum L. germinates normally, produces several nodes, and then above a sharp transition produces 2 to 3 bleached nodes, ceases growth, and eventually dies. Green nodes have normal chlorophyll content, absorption spectra, photosynthetic rates, and ultrastructure. In bleaching tissues, the chloroplasts degenerate rapidly, followed by extensive disruption and loss of the remaining cytoplasm and organelles. Application of tissue extracts of normal genotypes of pea, corn, and bean stimulates apical development of alt. The resulting tissues have essentially normal structure and function. Application of thiamine, thiamine monophosphate, and thiamine pyrophosphate also stimulate normal apical development at concentrations of 1 micromolar and above. Partial characterization of the stimulus from pea seed extracts is consistent with thiamine as the active factor.