Rootstock effects in grafted conifers: A review

The literature on rootstock effects (on scions) in conifers was reviewed, specifically: graft success, compatibility, size, reproduction, phenology, crown and needle characters, mineral contents, organic compounds, water relations, disease resistance and wood properties. Scions usually had higher graft success and less incompatibility on more closely related rootstocks although there were exceptions. Even intergeneric grafts have succeeded on occasion. Although there were marked rootstock effects on growth and reproduction, the effects did not follow a pattern with increasing relationship. It is also likely that some crown characters and the nutrient content of scions can be manipulated by the use of rootstocks. For many characters, a specific rootstock may give a desired result only for a limited number of scion types (species, cultivars or clones). With some exceptions, the review shows that the subject has not been comprehensively studied. Many of the studies were either short-term, inadequately replicated, or poorly designed to allow firm conclusions about rootstock effects. The physiological and biochemical mechanisms, which cause the changes seen in morphology, are not well understood. Further research and more comprehensive study of rootstock effects on scion biology are recommended.     

Family stability of wood specific gravity in Pinus tecunumanii established on three sites in South America

Wood specific gravity was determined for 29 half-sib families of 4-year-old Pinus tecunumanii from the Mountain Pine Ridge, Belize, planted at three locations in Brazil and Colombia. Although there was a significant (p 0.05) family by sites interaction (F × S), it was found that only 5 of the 29 families were major contributors. The test planting at the highest elevation (1750 m, La Arcadia, Colombia) was the most interactive site.CAMCORE Cooperative, College of Forest Resources, North Carolina State University     

Enterococcus faecalis senses target cells and in response expresses cytolysin

Many virulent strains of Enterococcus faecalis produce a two-subunit toxin, termed cytolysin. Cytolysin expression is regulated by one of the subunits (CylL(S)') through a quorum-sensing autoinduction mechanism. We found that when target cells are absent, the other subunit (CylL(L)') forms a complex with CylL(S)', blocking it from autoinducing the operon. When target cells are present, however, CylL(L)' binds preferentially to the target, allowing free CylL(S)' to accumulate above the induction threshold. Thus, enterococci use CylL(L)' to actively probe the environment for target cells, and when target cells are detected, allows the organism to express high levels of cytolysin in response.     

Phenological variation in height and diameter growth in provenances and families of loblolly pine

The phenology of 5- and 6-year old loblolly pine (Pinus taeda L.) trees was studied over two different growing seasons (1993 and 94) in southwest Georgia. These trees were from 7–9 open-pollinated families from each of four different provenances planted at two locations. The provenances were: Atlantic Coastal Plain (eastern SC), Gulf Hammock (north FL), Lower Gulf (south AL, MS) and Upper Gulf (north AL, MS). Provenances did not vary as to when height growth started in spring, but showed very significant differences for the date of growth cessation in fall. The Gulf Hammock source grew the most and also had the longest height growth period, while the Upper Gulf source was first to stop height growth and had the least annual height increment. Provenances were also significantly different for the date of cessation of diameter growth (a difference of 22 days between Gulf Hammock and Upper Gulf), and the order of cessation was the same as for height. Families within provenances were significantly different for date of cessation of height growth and diameter growth. When family means were considered across provenances, there was a correlation of 0.69 (p-value = 0.0001) between annual height increment and date of height growth cessation. There was a weaker association between faster growth and a longer growing season within provenances.