Maintenance respiration correlates with sugar but not nitrogen concentration in dormant plants

The range and source of variation in foliage respiration rate in the dorman t season were investigated for plants of Lycopodium annotinum L,, Pinus con torta Dougl, var. latifolia Engelm,, Picea abies (L,) Karst,, Andromeda pol ifolia L,, Calluna vulgaris (L,) Hull, Vaccinium myrtillus L,, Vaccinium vi tis-ideae L, and Empetrum hermaphroditum Hagerup. Field-grown plants were t ransferred to a cold room kept at 5 degrees C in late autumn and then analy sed for the foliage respiration rate in relation to nitrogen and sugar conc entration over a period of many weeks. Respiration rate varied 1.6-fold amo ng species at a given time, and decreased with time as long as plants remai ned dormant. Most of both sources of variation were accounted for by the sa me linear and positive correlation with total soluble sugar concentration, whereas no relationship with nitrogen concentration was found. The hypothes is presented is that respiration rate correlates with sugar concentration i n the dormant season because cellular sugar concentrations are much increas ed and, thereby, the costs of maintaining concentration gradients. Pinus co ntorta had a significantly higher respiration rate for a given sugar concen tration than any other species, and therefore suffered larger relative loss es of sugars when kept at 5 degrees C; possible reasons and consequences of this are discussed in relation to field performance.