DIRECT AND DELAYED COSTS OF REPRODUCTION IN AESCULUS-CALIFORNICA

(1) Reproduction in Aesculus californica involves both direct and delayed costs. In this shoot-level analysis, direct costs were measured as the total non-structural carbohydrate, nitrogen and total dry weight in reproductive tissues. Delayed costs were measured as deleterious effects of reproduction on growth and reproduction in the season following reproduction. (2) The costs of reproduction were unevenly distributed among shoots. Fruit-bearing shoots incurred the greatest direct and indirect costs. Mature fruits were produced on only 42% of flowering shoots following the abortion of more than 90% of bisexual flowers and young fruits. The dry weight allocated to reproduction on non-bearing shoots was only 12% of the amount allocated on fruit-bearing shoots. (3) A girdling experiment demonstrated that individual fruit-bearing shoots could not independently supply all the resources required in fruit development. (4) Fruit-bearing shoots incurred delayed costs not shared by other branches. In the season following reproduction, bud break on fruit-bearing shoots was significantly later than on non-bearing shoots. The dry weight and leaf area of new growth produced on previously fruiting branches was less than one third of that produced on non-fruiting branches. Leaf nitrogen concentration was also significantly lower on previously fruiting branches. In 1984, previously bearing branches were less likely to initiate inflorescences and mature fruits than were previously non-fruiting branches. The effect was not observed in 1985.