The Growth and Carbon Economy of Selection Lines of Lolium perenne cv. S23 with Differing Rates of Dark Respiration: 2. Grown as Young Plants from Seed

Young plants of two selection lines of Lolium perenne cv. S23with ‘fast’ and ‘slow’ rates of ‘maturetissue’ respiration were individually grown from seed,together with plants of S23, their common parent, in 9.2 cmpots in a controlled environment at 20/15 °C day/night temperatures. No significant differences were found between the genotypesin leaf extension and tiller production during this early stageof their growth. They did differ however, by an average of 26%,in the rate of dark respiration of fully expanded leaf laminae.The use of a simple model demonstrated that such a differencein respiration could alone account for the different rates ofdry matter production shown by the selection lines when grownas young crops from seed. Possible penalties of ‘slow’respiration are also considered. Lolium perenne L., ryegrass, respiration, maintenance respiration, stimulated swards, leaf growth, tiller production, carbon economy     

SOME ASPECTS OF THE STRUCTURE OF THE NERVOUS SYSTEM IN THE ANEMONE CALLIACTIS

In the light of existing work on tbe behavioral physiology ofthis anemone, the structure of parts of the neuroimiscular systemhas been examined in detail. In the sphincter region, the morphologicalbasis for rapid through-conduction and motor innervation isa network of bipolar nerve cells, which is connected to thesimilar retractor nerve-nets of mesenteries. Sphincter musclefibers are arranged at the periphery of tubes, which form ameshwork within the mesogloea. Bipolar nerve cells appear torun in these tubes. Neurites also reach the sphincter from theendodermal nerve-net by penetrating the mesogloea directly.The nerve-net over the circular muscle is richer than in otherparts of the column, but shows similar features. It includessmall multipolar cells of unknown function. Coordination between different parts of the anemone is discussedin terms of possible pathways for the transmission of excitation.For example, bundles of retractor and parietobasilar musclefibers continue from both surfaces of mesenteries into the mesogloeaof the pedal disk, suggesting a possible route for neuritespassing to or from the ectoderm. If confirmed, the existenceof this route could throw light on a number of sequences ofbehavior.