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We showed that temperature responses of dark respiration for foliage of Pinus radiata could be approximated by Arrhenius kinetics, whereby E(0) determines shape of the exponential response and denotes overall activation energy of respiratory metabolism. Reproducible and predictable deviation from strict Arrhenius kinetics depended on foliage age, and differed between R(CO2) and R(O2). Inhibition of oxygen reduction (R(O2)) by cyanide (inhibiting COX) or SHAM (inhibiting AOX) resulted in reproducible changes of the temperature sensitivity for R(O2), but did not affect R(CO2). Enthalpic growth--preservation of electrons in anabolic products--could be approximated with knowledge of four variables: activation energies (E(0)) for both R(CO2) and R(O2), and basal rates of respiration at a low reference temperature (R(REF)). Rates of enthalpic growth by P. radiata needles were large in spring due to differences between R(REF) of oxidative decarboxylation and that of oxygen reduction, while overall activation energies for the two processes were similar. Later during needle development, enthalpic growth was dependent on differences between E(0) for R(CO2) as compared with R(O2), and increased E(0)(R(O2)) indicated greater contributions of cytochrome oxidase to accompany the switch from carbohydrate sink to source. Temperature-dependent increments in stored energy can be calculated as the difference between R(CO2)DeltaH(CO2) and R(O2)DeltaH(O2).

Leader dieback associated with B deficiency in P. radiata D. Don plantations was treated with borax applied at rates of 50, 100 and 150 kg ha -1. This initially increased B in foliage from 5 to 40, 80 and 110/xg g-~ respectively, and was followed by a rapid decline and stabilisation at around 25/xg g-I for the duration of the study. Annual fluctuations in foliage B levels were strongly correlated with rainfall during the preceding spring and summer. Uptake of N, P and K increased as a result of applied B and comparison of the distribution of these nutrients in crowns of fertilized and unfertilised trees six years after application indicated continued uptake of these nutrients probably as a result of improved root growth due to B. Foliage concentrations of B like N, P and K, increased in young needles towards the upper crown and this, together with a decline in needle concentrations of B as foliage aged, indicated some redistribution of B from older to new foliage. A limit of 5/zg g-1 was found below which little redistribution seems to occur.Application of B prevented further leader dieback, improved apical dominance and height growth and increased volume production by 25 m 3 ha-1 at age 8 years. Differences between application rates of B were not significant in terms of growth.