A drop in ambient temperature which increases thermogenesis is the fundamental factor stimulating ultrasonic vocalization in newborn rodents. Neonatal mice modify ultrasonic calling in response to olfactory cues. When removed from the nest and cooled, CBA-strain mouse pups produced ultrasonic calls on the 3rd, 5th and 7th days of life. The presence of conspecific bedding affected their ultrasonic vocalization. The number and duration of calls were higher in 3-day-old CBA pups exposed to bedding of C57BL lactating females than in newborns tested in the presence of bedding from CBA lactating females. This indicates that CBA pups discriminate between the odours of the two genotypes. The influence of postnatal experiences on the ability to differentiate odours was investigated. Three-day-old CBA mice nursed by their own mothers vocalized at higher frequencies than did newborns fostered by C57BL lactating females. It is suggested that ultrasonic vocalization in CBA pups is affected by genetic factors and postnatal environmental conditions.
Morphological variability in wood fibres of Lonchocarpus sericeus (Poir.) Kunth ex DC. (Leguminosae), a tropical hardwood tree with doublestoreyed cambium, was examined in thin tangential and transverse sections as well as in macerations of wood tissue. Occurrence of characteristic protrusions (lateral expansions) was detected on the extended part of the main fibre body. Distance between the adjacent protrusions corresponded to the height of a storey (horizontal tier) of the cambial initials. Rays were shorter in height than the neighbouring fusiform initials and therefore unable to reach the boundary of the storey. This situation facilitated the lateral expansion of the adjoining fibres during their apical elongation by intrusive growth. The presence of the characteristic protrusions on the fibre body thus indicated that the given fibre was associated with a double-storeyed cambium having rays shorter than the length of fusiform initials. The ultimate shape of fibres was thus correlated to the height of storeys and the height and width of rays.
The use of automated techniques for image analysis of microscopic wood specimens together with new procedures for the preparation of stained xylem tissue support the use of quantitative wood anatomy. These techniques and procedures are especially useful in the studies of retrospective analysis of xylem phenology, reaction(s) of trees to stressful conditions of growth, or reconstruction of long-term growth trends. The unresolved technical problems during the digitalization of cross sections from entire increment cores were stabilization and precise shifting of long microscopic specimens onto the optical microscope stage. For this reason, we have developed a long slide holder for microscope stages in two versions: the basic one allowing stabilization and manual shifting, and the advanced one for stabilization and mechanical shifting. Both versions of the adapter speed up the work with long slides, improving the quality of panoramic images of microscopic specimens.
It is well documented that apical elongation of fusiform cambial initials through extension of their longitudinal edges, and their intrusion between tangential walls of the neighbouring initials and their closest derivatives cause rearrangement of fusiform cells, without increasing the cambial circumference. However, the concurrent rearrangement of rays is not fully understood. This study deals with Pinus sylvestris L., Tilia cordata Mill. and Hippophaë rhamnoides L., possessing a nonstoreyed, storeyed and double-storeyed type of cambium, respectively, and shows that the mechanism for rearrangement of ray initials is similar to the one proposed for fusiform initials, and includes multiplication of ray initials by anticlinal divisions, intrusive growth of ray initials, elimination of ray initials caused by intrusive growth of neighbouring fusiform initials, and transformation of ray initials into fusiform initials. Intrusive growth of a ray initial does not necessarily lead to the formation of a new fusiform initial, as it is dependent on the extent of the intrusive growth taken place. The extent of rearrangement of cambial cells is determined by the intensity of events occurring among the fusiform as well as ray initials. Intrusive growth of these initials does not influence the size of the cambial circumference.
Our study investigated the effect of stem temperature increase on xylem formation in Robinia pseudoacacia tree-trunks, caused by direct exposure to solar radiation. It is important to determine factors which may improve the concentricity of deposited wood tissue and intensify xylogenesis because a strong irregularity of wood tissue deposited in the radial direction in mature trees of R. pseudoacacia reduces the commercial value of the wood. Samples of vascular cambium along with adjacent tissues were collected from the southern (illuminated) and northern (shaded) side of tree-trunks growing in the inner and peripheral (thus exposed to direct sunlight) zones of the research plot. Sampling was performed several times during the growing season. The collected material was examined by epifluorescence microscopy and the thickness of deposited tissue comprising cambial xylem derivatives was measured. Deposition of a markedly greater amount of xylem on the southern side of tree-trunks in the peripheral zone of the plot was observed before full leaf development. Instrumental climatic data confirmed that in the early stage of the growing season, temperature on the southern side of the peripheral zone tree-trunk was higher than on the northern side. No clear response in terms of directional deposition of xylem was noticed in the inner zone trees and in peripheral zone trees after full leaf development. This study highlights the importance of temperature increase, caused by solar radiation, for R. pseudoacacia xylogenesis, which may be considered as a factor that affects the course of the radial growth before full leaf development.