An Analysis of Growth of Oil Palms under Nursery Conditions: I. Establishment and Growth in the Wet Season

Growth of oil palm seedlings over the period 2–31 weeksafter planting in the nursery was studied using growth-analysistechniques. Curves of the Gompertz type were fitted to the basicdata of plant dry weight and leaf area, and from the equationsof the fitted curves, net assimilation rate (E_A), relative growth-rate(Rw), and relative leaf growth-rate (R_A) were calculated. The low values of E_A (0.16-0–31 g/dm²/week) and Rw (1.4–2.2per cent./per day) confirm earlier work on oil palm seedlings.The time trend of increasing E_A and R_W over the period studiedis associated with steadily increasing solar radiation overthe second half of the period. Leaf-area ratio is markedly affected by transplanting, and asthis unbalance of leaf area/total dry weight has been shownto be associated with low rates of EA in seedlings, it is suggestedthat the low values of E_A and R_W in the first half of the experimentalperiod are due to the effect of transplanting. These findings are discussed in relation to current nurserypractice.     

Changes in Endogenous Gibberellin Levels in Tulipa Bulblets during Ontogeny

The endogenous gibberellin activity of Tulipa gesneriana cv.Apeldoorn bulbiets of field-grown mother bulbs was determinedduring ontogeny by paper and gas-liquid chromatography and thedwarf pea bioassay. It was shown that the gibberellin activityof bulblets increased dramatically in November-March and declinedsharply in April-July. The increase in gibberellin-like substanceswas considered to be derived primarily by synthesis within thebulblets with possible contributions via translocation fromthe mother bulb scales, roots and shoots. Gibberellin A₁₃ wastentatively identified by gas-liquid chromatography but theother components of the bulbiet extracts remained unidentified.     

Differential permeability of rivers to raccoon gene flow corresponds to rabies incidence in Ontario, Canada

The correlation of landscape features with genetic discontinuities reveals barriers to dispersal that can contribute to understanding present and future spread of wildlife diseases. This knowledge can then be used for targeting control efforts. The impact of natural barriers on raccoon dispersal was assessed through genetic analysis of samples from two regions, Niagara ( N  = 666) and St. Lawrence ( N  = 802). These areas are transected by major rivers and are at the northern front of a raccoon rabies epizootic. Genetic clusters were identified in each region using Bayesian clustering algorithms. In the Niagara region, two clusters were identified corresponding to either side of the Niagara River. For the St. Lawrence region, spatially congruent clusters were not identified, despite the presence of the intervening St. Lawrence River. These genetic data are consistent with raccoon rabies incidence data where rabies has been detected across the St. Lawrence River in Ontario while no cases have been detected in Ontario across the Niagara River. This is despite expectations of rabies incidence in Niagara before the St. Lawrence based on the progression of rabies from New York. The results from the two regions suggest different permeabilities to raccoons between New York and Ontario that may be attributed to the rivers. However, other factors have also been explored that could contribute to this difference between these study sites including the shape of the landscape and resource distribution.