Prolonged Infusion of Fluids into Tree Seedlings Using Ascorbic Acid

A method was developed to infuse liquids into the stems of three-year-oldCercis canadensis L., Liriodendron tulipifera L., and Tiliacordata Mill. seedlings and to monitor the movement of fluidinto the stems. Ascorbic acid (14.2 mM) added to the infusionliquid, could increase the initial rate of fluid uptake 2- to3-fold compared with distilled water control treatments. Theascorbic acid treatment also prolonged fluid uptake about 4d longer than distilled water treatments. The effect of ascorbicacid on fluid uptake could not be correlated to the solutionpH, the antibiotic effect of high ascorbic acid concentrations,or to seedling height, trunk diameter or projected leaf area.Data did, however, suggest that the increased fluid uptake rateand the prolonged fluid uptake may be related to the anti-oxidantproperty of ascorbic acid. The accumulation of 1.0 g of ascorbicacid in 60 to 100 cm tall C. canadensis and L. tulipifera seedlingsdid induce defoliation and lateral bud break. The data presentedmay be useful in developing techniques for prolonged infusionof therapeutic compounds into trees and for studying, in vivo,wound response to xylem tissue. Key words: Ascorbic acid, liquid influsion, tree seedlings     

Food resource allocation patterns in lactating females in a long-term selection experiment for litter size in mice

Resource allocation patterns, as quantified by residual food intake (RFI), and the consequences for offspring development were investigated during lactation in 96 females of a mouse line selected for 104 generations for high litter size at birth (S-line) and in 87 females of a non-selected control line (C-line). Litters of 45 C-line dams (Cs) and 48 S-line dams (Ss) were standardised (s) at birth; other dams (ns) supported total number of pups born (Cns and Sns, respectively). RFI during lactation was significantly lower in Sns-dams than in C-line dams and Sns-dams. After weaning Sns-dams seemed to be able to restore the negative resource situation. Sns-pups were about 25% less mature than Cns-pups at all times. Maturity was similar for Cs- and Ss-pups from 2 d in lactation on, and about 18% and 53% higher than Cns- and Sns-pups. The pre-weaning mortality rate was significantly higher in Sns-litters (35.6 ± 2.76) than in Cns-litters (4.95 ± 2.23). The results suggest that S-line dams allocated considerably more resources to maintenance of offspring than C-line dams. This was insufficient to provide the offspring with an adequate amount of resources, resulting in reduced pup development and increased pre-weaning mortality rates.     

Fire‐related cues and germination from the soil seed bank of senescent remnants of mallee vegetation on Eastern Kangaroo Island

Plant communities dominated by narrow‐leaved mallee (Eucalyptus cneorifolia) are almost entirely confined to north‐eastern Kangaroo Island, South Australia, an area which has been extensively cleared for agriculture. Consequently, surviving examples consist mostly of small remnants which are thought to be senescent due to the exclusion of fire. This senescence is associated with the loss of many native understory species. Prescribed burns have been suggested as a management tool to stimulate the restoration of native plants from the soil seed bank; however, no seed bank studies have previously been conducted on Kangaroo Island and the seed bank literature usually focuses on particular species rather than on plant communities. We conducted an experiment to investigate the effects of the fire‐related cues heat and smoke on the germination of plants from the seed bank in soil sampled from 10 long‐ungrazed narrow‐leaved mallee sites on Kangaroo Island. Eighty trays of soil were monitored in a controlled glasshouse for five months after being subjected to heat and/or smoke treatments. The overall number of native, but not exotic, plant species germinating from the soil seed bank was significantly increased by all three fire‐related treatments (heat, smoke and heat plus smoke) compared with the control (no fire‐related treatment). Different plant life forms exhibited varying responses to heat and smoke treatments. The results of this study illustrate that the application of fire‐related treatments to soil seed banks in controlled glasshouse conditions can stimulate the recruitment of native species, including several species of conservation concern. These findings also indicate the potential of using these treatments for the ex situ germination of fire dependent species for revegetation purposes and indicate aspects of prescribed burns that may be important for restoring different components of native vegetation.