Ethylene and carbon dioxide production by developing strawberries show a correlative pattern that is indicative of ripening climacteric fruit

Laser photoacoustic spectroscopy continuously quantified the ethylene (C₂H₄) produced by strawberry flowers and fruits developing in planta. C₂H₄ was first detected as flower buds opened and exhibited diurnal oscillations (to approximately 200 pl flower^-1 h^-1) before petal abscission. Exogenous application of silver thiosulphate (STS) to detached flowers inhibited petal abscission and flower senescence. In fruit, C₂H₄ production was maintained at a 'low level' (10-60 pl fruit^-1 h ^-1) until fruit expanded when levels increased in a diurnal pattern (to 200 pl fruit^-1 h^-1). After expansion, C ₂H₄ production declined to a low level until fruit attained the red-ripe stage for at least 24 h. After this time, C ₂H₄ levels increased linearly (no diurnal fluctuation) to approximately 1 nL fruit^-1 h^-1. Twenty-four hours after the re-initiation of C₂H₄ production by red fruit, CO ₂ levels increased approximately three-fold, indicative of a respiratory climacteric. STS applied to fruits developing in planta and dissected fruit parts ex situ established that C₂H₄ production is regulated by negative feedback until fruits had expanded. The C₂H₄ produced by red-ripe fruit was regulated by positive feedback. Anti-1-amino-cyclopropane-1-carboxylic acid oxidase IgG localization identified immunoreactive antigens of 40 and 30 kDa (M_r) within the fruit achenes of expanding and red-ripe fruit. Analysis of dissected fruit showed that seed C₂H₄ accounts for 50% the C ₂H₄ that is detectable from ripe fruit.