The Gibberellin-like Substances and Growth Inhibitors in Developing Strawberry Leaves

Gibberellin-like substances and inhibitors present in extractsof runner buds, and unfolding and mature leaves of strawberryhave been fractionated and compared. The runner-bud water-solubleresidue was more strongly inhibitory than that from unfoldingand mature leaves. The crude acid fraction from unfolding andmature leaves contained appreciable amounts of an inhibitor,probably abscisic acid, which was not detected in the buds.The unfolding leaves had a higher concentration of acidic gibberellin-likesubstances than either buds or mature leaves; they also containeda number of neutral gibberellin-like substances. Mature leaveshad a low concentration of gibberellin-like substances, allof which were acidic. A number of these were highly non-polartypes, not found in the buds or unfolding leaves.     

A Study of the Seed Proteins of Synthesized Brassica napus with Respect to its Parents

The parental and hybrid seed of three synthesis experiments(B. oleracea x B. campeslris = B. napus) has been analysed byacrylamide gel electrophoresis for general proteins and certainenzymes. A serological study has been made of one of the synthesisexperiments. The protein and enzyme patterns of the newly establishedhybrids are compared with those of two well-established varietiesof B. napus. The results suggest that the hybrid seed has noprotein which differs from those in the parental types, andthat the protein spectrum of the hybrid is a summation of someof the proteins found in the parents. The analytical methodsemployed are discussed with particular reference to their valueas an assessment of plant genotype.     

Electrical Coupling, Potentials, and Resistances in Oat Coleoptiles: Effects of Azide and Cyanide

Electrophysiological measurements were made on oat coleoptile(Avena sativa L. cv. Victory) parenchyma cells. Both 1 mM potassiumcyanide and 1 mM sodium azide cause reductions in cell restingpotential and electrical coupling and an increase in the combinedtonoplast and plasmalemma resistance. The reduction in coupling is probably attributable to a decreasein current flow through plasmodesmata, resulting from an increasein plasmodesmatal resistance. Potassium cyanide also induces some callose formation withincell walls and this may contribute to the observed reductionin coupling. However, sodium azide does not induce callose formation.Presumably other processes are involved in the reduction ofcoupling which are not attributable to callose.     

Enzyme Distribution Between the Cortex and the Infected Region of Soybean Nodules

Analysis of the distribution of enzymes of carbohydrate, carboxylicacid and nitrogen metabolism in nodule tissues prepared by protoplastisolation techniques has led to some confusion about their whereabouts.In this study nodule cortical and central (infected) tissuewas separated manually using a scalpel blade. Protein contents of whole nodules, central region and cortexwere found to be 19, 25 and 5-0 mg g^–1 fresh weight, respectively.Specific activities of glutamine synthetase (GS), phosphoenolpyruvatecarboxylase (PEPC), invertase (INV) and sucrose synthase (SS)were higher in the central region than in the cortex. The reversewas true for UDP glucose pyrophosphorylase (UDPGPP), phosphoglucomutase(PGM) and phosphoglucose isomerase (PGI). The central (infected) region represented a minimum of 65% ofthe nodule fresh weight. Calculations based on this estimateand on the activities per gram fresh weight indicate that thebulk of the potential enzyme activity is located in the centralregion. This was particularly so for SS, INV and GS where greaterthan 96% of the relevant activity was located in the centralregion. Even the enzymes which had greater specific activitiesin the cortex (UDPGPP, PGM and PGI) were, in fact, predominantlyfound in the central region (86, 81, and 85%, respectively).The conclusion from this data must be that most metabolism inthe nodule is likely to occur in the central region, althoughthis does not negate the importance of the cortex in carbonand nitrogen flux. Key words: Glycine max, soybean, nodules, cortex, infected region, enzymes     

Density Effects on the Size Structure of Annual Plant Populations: An Indication of Neighbourhood Competition

Size variability among plants has been observed to increasewith higher stand density, leading to the speculation that resourcedistribution among competing plants is primarily asymmetricrather than symmetric. The relationships between size variability,stand density, and type of resource distribution among competingplants were investigated using a spatially explicit, individual-plantmodel of annual plant population dynamics. When plants variedin neighbourhood competition, size variability increased withhigher stand densities whether shared resources were symmetricallyor asymmetrically distributed among competing plants. Size variabilitydid not increase with higher stand densities when neighbourhoodcompetition was constant for all plants. These simulations indicatethat increased size variability among competing plants doesnot distinguish between symmetric and asymmetric resource distribution,but rather is direct evidence for neighbourhood competition. Size hierarchy, neighbourhood competition, density effects, asymmetric competition, symmetric competition