Heat production and respiration by broccoli florets during senescence at 20°C

Broccoli ( Brassica oleracea L. var. italica ’ Shogun’) branchlets were treated with water or 50 ppm 6‐benzylaminopurine (BAP) and stored for up to 5 days in the dark at 20°C. Florets were removed from the branchlets and subjected to measurements of metabolic activity (heat production or oxygen uptake) and colour change. Water‐treated florets turned yellow much sooner than did BAP‐treated florets. Heat production and respiration decreased after both treatments, and then increased dramatically between 24 and 96 h in water‐treated florets, but increased only slightly in BAP‐treated florets. We discuss possible causes for the higher metabolic activity in water‐treated florets.