The Induction and Development of Potato Microtubers In Vitroon Media Free of Growth Regulating Substances

Reliable microtuber production has been obtained by culturingnodal explants of potato on Murashige and Skoog medium withoutthe addition of growth regulating substances. The use of sucroseat 8 %, as compared with 4 or 12%, advanced the initiation oftuberization and gave more and larger microtubers. A periodof 1 month under 16 h days, followed by transfer to 8 h photoperiodsgave most rapid microtuber development. A reduction in the totalnitrogen supply or an increase in the ratio of ammonium to nitratereduced the size and number of microtubers Potato, Solanum tubersum L;, microtubers, in vitro induction and development, sucrose, photoperiod, nitrogen nutrition     

The development of the brine shrimp Artemia salina (L.): a morphometric approach

Growth allomentry in the development of the brine shrimp Artemia salina (L.) was studied. Body width and abdomen length show a negative allometric relation to body length ( k =0.35 and 0.72 respectively) over th eight instars studied. Antennule length shows a negative allometric relation in respect to body length, with a change in the value of the growth constant at Instar Five from 0.31 to 0.75. Thoracic limb length shows a high positive relation to body length ( k =3.0) until Instar Six, when a negative allometric phase ( k =0.4) follows. A change in the sign of the growth constant from positive ( k =0.45) to negative ( k =-1.4) is noted for the length of the 2nd antenna in relation to body length.     

Seed Development in the Recalcitrant Species Quercus robur L: Water Status and Endogenous Abscisic Acid Levels

Water status and endogenous ABA levels were measured duringthe development of the embryonic axis and cotyledons in fruitsof Quercus robur L. As dry matter accumulated in the embryoduring development, both moisture content and osmotic potential(     

Temporal variation in body composition (C : N) helps explain seasonal patterns of zooplankton δ13C

1. The stable carbon isotope ratio δ¹³C is a useful tracer of energy flow in lake food webs, and the zooplankton signature is commonly used to establish a baseline for the pelagic habitat. However, sources of temporal variability in the δ¹³C of different zooplankton taxa are rarely considered. 2. Here, we investigate to what extent temporal variation in the δ¹³C of particulate organic matter (POM) (<41 μm) and the C : N of zooplankton can explain the temporal variability in δ¹³C of freshwater zooplankton. We compare temporal patterns of δ¹³C and C : N for Daphnia, Hesperodiaptomus franciscanus and Leptodiaptomus tyrelli over a 6‐month period at four sites in two oligotrophic lakes. 3. In all three taxa, seasonal variation in zooplankton C : N explained more of the variation in zooplankton δ¹³C than did the δ¹³C of POM. This suggests that variation in the lipid content of zooplankton can strongly influence temporal variation of δ¹³C in zooplankton. 4. Using these data, we evaluate procedures that estimate the δ¹³C of only the non‐lipid component of zooplankton. If zooplankton lipids are primarily dietary in origin, than extracting lipids or ‘normalising’δ¹³C based on C : N will exclude a major dietary source, and therefore may be inappropriate. 5. We conclude that temporal variation in body composition (C : N) of zooplankton can significantly influence the temporal variation of zooplankton δ¹³C signatures.     

Regeneration in the auditory system of nymphal and adult bush crickets Tettigonia viridissima

Regeneration and reestablishment of synaptic connections is an important topic in neurobiological research. In the present study, the regeneration of auditory afferents and the accompanying effects in the central nervous system are investigated in nymphs and adults of the bush cricket Tettigonia viridissima L. (Orthoptera: Tettigoniidae). In all animals in which the tympanal nerve is crushed, neuronal tracing shows a regrowth of the afferents into the prothoracic ganglion. This regeneration is seen in both adult and nymphal stages and starts 10–15 days after nerve crushing. Physiological recordings from the leg nerve indicate a recovery of tympanal fibres and a formation of functional connections to interneurones in the same time range. Electrophysiological recordings from the neck connective suggest additional contralateral sprouting of interneurones and the formation of aberrant connections. The regeneration processes of the tympanal nerve in nymphal stages and adults appear to be similar.