AUTOLYSIS IN HERBACEOUS, DICOTYLEDONOUS PLANTS - EXPERIMENTAL MANIPULATION OF PITH AUTOLYSIS IN SEVERAL CULTIVATED SPECIES

Pith autolysis, a condition in which dicotyledonous herbaceous plants have a hollow stem, results from the autolysis of a plant's storage pi th. Our central hypothesis concerning the aetiology of pith autolysis states that the carbon from the pith is transported to the growth regi ons of the plant and used at times when the plant cannot meet its carb on needs by photosynthesis alone. According to this hypothesis, accele rated growth should increase pith autolysis. We here provide supportin g evidence for the central hypothesis. More pith autolysis was found i n faster growing tomato varieties than in dwarf varieties. More pith a utolysis was found in both beans and tomatoes treated with GA(3) than in controls. More pith autolysis was found in leggy bean plants grown in low light than in normal plants grown under normal light conditions . Pith autolysis decreased in both beans and tomatoes when mechanicall y perturbed or sprayed with paclobutrazol, both treatments that reduce d growth. The stems of buckwheat plants that were flowering showed gre ater pith autolysis and therefore were more hollow than plants which w ere not flowering or which had the incipient flowers pinched off. This indicated that carbon from the storage pith may also be used in the f ormation of reproductive structures which require extra carbon. Also i n support of the central hypothesis is the prevention of pith autolysi s by the addition of extra carbon to the plant, in the form of an incr eased CO2 concentration of the surrounding air. (C) 1995 Annals of Bot any Company