Endogenous Growth Regulation in Carpophores of Agaricus bisporus

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Abstract
Growth curves for carpophores of Agaricus bisporus var. albidus (Lange) Singer showed that the average maximum growth rate was 1.4 cm/day at 15-17[degree]C, and that the increase in cap diameter was numerically equal to the carpophore length up to 5 cm, when the cap began to flatten. Stipe elongation and cap expansion ceased at the same time. Removal of portions of the cap resulted in a slight decrease in total stipe growth and maximum growth rate compared to intact specimens. After decapitation the stipe growth decreased without recovery during the 1st day but did not stop until 3-4 days after the operation except at less than 2 cm length, where it stopped during the 1st day. This residual growth was studied in detail. There is no regeneration of a "physiological apex" either in the stipe or in the cap trama. Growth studies after selective removal of cap trama or lamellae showed that the lamellae are the regulatory center of stipe growth and also of cap trama expansion. There is no synergistic effect on stipe growth between the lamellae and the cap trama. The action of the lamellae cannot be attributed to water relations and must be due to one or more growth factors which are not synthesized elsewhere in the fruit body. Transmission of the growth-promoting effect to the stipe seems to take place either through hyphae at the base of the cap adjacent to the lamellae, or directly through the lamellae. Transmission through the main body of the cap trama seems to be impeded though not completely prevented. Cap portions or lamellae alone left at 1 side of the stipe gave strong negative curvatures during the early phase of elongation, while cap portions without lamellae gave small curvatures or none. Unilateral cap portions with lamellae also gave negative curvatures during a later phase of elongation (around 5 cm length) but these were smaller than in younger specimens. Significant unilateral injury of the stipe surface causes curvatures.

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