Short-term storage of carbohydrate in stem tissue of apple (Malus domestica), a woody perennial: evidence for involvement of the apoplast.

This work investigates the pathway and mechanism for lateral retrieval of carbohydrate into the transport phloem of apple stems (Malus domestica Borkh.). A heat exchanger was set up on the stem, allowing rapid chilling and subsequent re-warming of stem segments while the time course of axial transport of C-labelled photoassimilate was measured at a position ∼65 mm downstream of the heat exchanger.

Foliar 15N natural abundance indicates phosphorus limitation of bog species.

Foliar delta15N, %N and %P in the dominant woody and herbaceous species across nutrient gradients in New Zealand restiad (family Restionaceae) raised bogs revealed marked differences in plant delta15N correlations with P. The two heath shrubs, Leptospermum scoparium (Myrtaceae) and Dracophyllum scoparium (Epacridaceae), showed considerable isotopic variation (-2.03 to -15.

Unexpectedly diverse Mesorhizobium strains and Rhizobium leguminosarum nodulate native legume genera of New Zealand, while introduced legume weeds are nodulated by Bradyrhizobium species.

The New Zealand native legume flora are represented by four genera, Sophora, Carmichaelia, Clianthus, and Montigena. The adventive flora of New Zealand contains several legume species introduced in the 19th century and now established as serious invasive weeds. Until now, nothing has been reported on the identification of the associated rhizobia of native or introduced legumes in New Zealand.

Direct measurement of release and assimilation of ammonia in the Gunnera-Nostoc symbiosis.

In Gunnera, Nostoc cells invade secretory tissue forming well defined symbiotic areas within the stems and are termed internal nodules (Silvester, 1976). Excised, but intact, internal stem Nostoc nodules taken from Gunnera magellanica show light-stimulated nitrogenase activity and release a small, but measurable, proportion of their current N fixation as NH into the external solution. When nodules are disrupted and Nostoc extracted anaerobically, 90% or more of the estimated N fixation is released from the Nostoc cells as NH into the surrounding medium.

Effects of branch length on carbon isotope discrimination in Pinus radiata.

Gas exchange was measured on a pruned Pinus radiata D. Don hedge and on a long-branch P. radiata tree near Hamilton, New Zealand, in spring 1993 when soil water content was close to field capacity.