Imbibitional Stress and Transverse Cracking of Bean, Pea, and Chickpea Cotyledons

Abstract

Transverse cracking was examined in cotyledon tissue of snap bean ( Phaseolus vulgaris L. ‘Apollo’), pea ( Pisum sativum L. ‘Garfield 81’), and chickpea ( Cicer arietinum L. ‘Surutato 77’). The hypothesis that imbibitional cracks develop along lines of least resistance or along preexisting cracks was evaluated. Columns of tissue were cut from cotyledons. Time from the start of imbibition to detection of the first crack was compared between whole bean cotyledons and columns. Bean columns cracked transversely with respect to the long axes of the columns. They did not crack longitudinally, even if the long axis of a column was originally perpendicular to the long axis of the cotyledon. These results do not support the hypothesis that imbibitional cracks form along preexisting cracks or along lines of weakness. Imbibitional stresses induced new cracks to form. The mean time to first crack and SE associated with its measurement were both significantly reduced in columns relative to the corresponding values for whole cotyledons (40 ± 2.6 and 100 ± 8.0 min, respectively) at an imbibition temperature of 19.3°C. Pea and chickpea cotyledon tissues also cracked transversely when they were cut into long, narrow columns.