Improvement of the heat pulse method for determining sap flow in trees

Abstract. The heat pulse method for determining sap flux in large woody sterns was modified for easier field operation. It uses the measurement of the time elapsed between heat pulse release by a line heater radially inserted in the stem, and the occurrence of maximum temperature 15 mm downstream of the heater. This spacing between heater and thermometer is critical to the reliability of the measurement. Calculations using uncorrected theory provide estimates of the sap flux density in stems with both uniform and non-uniform cross-sectional distribution of conducting tissues which are about 55% of the actual sap flux density. This factor results from insufficient thermal homogeneity between tissues where sap flow occurs and tissues where sap flow has been interrupted.
Sap flow in trunks of citrus trees was inferred from measurements of the cross-sectional distribution of sap flux density. Variability of sap flux density is specific to each trunk and is time-dependent and imposes multiple radial and angular measurements. The method was checked in a citrus trunk ramified into three branches. Instantaneous determinations of the flow in the trunk and in the branches differed by less than 5.7%. The daily values agreed within 2.8%.     

Association of vegetative and reproductive organs of platanoids (Angiospermae): significance for systematics and phylogeny

Some examples of association between platanoid leaves and various reproductive structures are considered. The expediency of determining dispersed Cretaceous platanoid leaves using a morphological system that is independent of the system of modern plants is discussed. It is confirmed that leaf structures are more conservative than reproductive organs. It is proposed that, in the geological past, there was a polymorphic group that was probably represented by extinct families which gave rise to modern families (in particular, Platanaceae and Hamamelidaceae).     

Vegetative and reproductive structure of the extinct Platanus neptuni from the Tertiary of Europe and relationships within the Platanaceae

Platanus neptuni (Ettingshausen) Bek, Holý & Z. Kvaek was a conspicuous warm-temperate to subtropical element of Late Eocene to Late Miocene European floras. In our concept, the P. neptuni plant includes not only globose infructescences upon which the species epithet is based, but also staminate and pistillate inflorescences and distinctive stipulate foliage. The leaves range from simple (P. neptuni morphoforma reussii (Ett.) comb. et stat. nov.) to trifoliolate (P. neptuni morphoforma fraxinifolia (Johnson & Gilmore) comb. et stat. nov.) and sometimes quinquefoliolate (P. neptuni morphoforma hibernica (Johnson & Gilmore) comb. et stat. nov.) with unlobed elliptical to obovate laminae that are uniform in venation, marginal serration, and epidermal structure. Foliar twigs confirm that the leaves are deciduous, with each petiole base enveloping a bud, as in extant Platanus subgen. Platanus. Platanus neptuni differs from extant species of the genus by large peltate glandular trichomes on the fruits and leaves, a prominent circumscissile rim on the stalk below the inflorescence, as well as by the tendency for compound foliage. These characters justify its position within an extinct subgenus of the Platanaceae (Platanus L. subgen. Glandulosa Z. Kvaek, Manchester & Guo). Platanus neptuni was common in mesic humid subtropical forests on volcanogenic subtrates and at sea shores.     

Mesofossils with platanaceous affinity from the Dakota Formation (Cretaceous) in Kansas, USA

The Platanaceae holds a basal position in the phylogeny of eudicots and therefore is of great interest to angiosperm systematists. The fossil record of the family is found in strata ranging from the Cretaceous to Recent in America, Europe and Asia. The research on the Platanaceae in the Dakota Formation can be traced back to 19th century; however, mesofossils of reproductive organs of the Platanaceae were never reported in the Midwest of North America before. This paper reports several specimens of Friisicarpus (Platanaceae) from the Dakota Formation in Kansas, USA. It complements the existing fossil records, and provides more information on reproductive biology of the family. The comparison with similar fossils from eastern North America and Europe provides some hints on biostratigraphy of the Cretaceous.