Polyamines in normal and auxin‐induced strawberry fruit development

Abstract

The possible involvement of polyamines during strawberry (Fragaria×ananassa Duch.) fruit development was investigated. Putrescine, spermidine, and spermine were identified in strawberry receptacles and achenes at all stages of development. Total (free) polyamine levels decreased from a maximum of 485 nmol g−1 fresh weight at pollination to a minimum of 55 nmol g−1 fresh weight in ripe receptacles. Total polyamine concentrations during corresponding stages of development were consistently higher in achenes than in receptacles, and ranged from 891 to 203 nmol g−1 fresh weight. Removal of achenes from the surface of developing receptacles 10 days after pollination reduced receptacle growth, and re‐initiation of growth by application of 1 mMα‐naphtaleneacetic acid (α‐NAA) was accompanied by a rapid increase in polyamine concentrations 24 h after treatment. Polyamine content per receptacle increased >3‐fold in normally developing receptacles and in de‐achened, auxin‐treated receptacles 10 days after removal of achenes, but did not increase during this period in de‐achened receptacles not treated with exogenous auxin. α‐NAA increased growth and polyamine levels to a greater extent than the structurally related, but less effective auxin, β‐NAA. Polyamine concentrations in receptacles with intact achenes remained similar to those of auxin depleted (de‐achened) receptacles, implying that the concentration of these compounds may not be limiting following achene removal.