Broccoli growth parameters and level of head infestations in simple and mixed plantings: Impact of increased flora diversification

The impacts of interplanting broccoli, Brassica oleracea var. italica L., with chili pepper, Capsicum annuum L., or yellow sweetclover (YSC), Melilotus officinalis L., on broccoli growth parameters and levels of lepidopteran head infestations were studied during two field seasons (winter & summer). During both seasons, several broccoli growth characteristics (e.g. plant vertical area, whole plant biomass, etc.) were significantly reduced in broccoli‐YSC habitats. However, broccoli heads in broccoli‐YSC habitats did not differ significantly in size from other treatment habitats. Additionally, these heads contained the lowest mean lepidopteran contaminants per broccoli crown during the winter season. During this period, the average number of lepidopteran contaminants per broccoli head was more than twice that in monoculture and pepper intercropped broccoli than in broccoli‐YSC habitats. During the summer experiment, the average number of lepidopteran contaminants per broccoli head was greater in pepper intercropped broccoli than in both monoculture and YSC interplanted broccoli. Potential causes of broccoli growth differences and their relationship to lepidopteran ovipositional behavior are discussed.     

THYSANODONTINAE: A NEW SUBFAMILY OF THE TROCHIDAE (GASTROPODA)

New genera Thysanodonta, Carinastele and Herbertina are referredto a new subfamily of the Troch-idae, Thysanodontinae, on thebasis of extremely distinctive jaw and radula. At up to 1400times longer than broad, the teeth are the most slender of anyknown gastropod, and they are unique among archae-ogastropodsin having harpoon-like tips with back-wardly inclined barbs.While food and feeding mode are unknown, it is suggested thatthey feed suctorially, perhaps on cnidarians. New species describedare Thysanodonta aucklandica, T. wairua, Carinastele kristelleae,C. jugosa, and C. coronata from New Zealand, T. boucheti fromNew Caledonia, and Herbertina eos and H. cognata from SouthAfrica. The Tasmanian Basilissa nicetarium Hedley & Mayis tentatively referred to Carinastele (Received 23 September 1987;     

A Mobile Apparatus for Measuring Leaf Photosynthesis in the Field

An apparatus is described that has been designed to measurethe gas exchange of individual cereal leaves in the field, usinginfrared gas analysis. Measurements on leaves of winter wheatshowed that there was true saturation of net photosynthesisat high irradiances but as irradiance decreased there was aproportional decrease in net photosynthesis. Measurements madeon wheat plants grown in a controlled environment, for comparison,showed the photosynthesis–light response curve to be betterfitted by a rectangular hyperbola. This dissimilar responseof photosynthesis to irradiancc for plants grown in controlledenvironments indicates the possible problems of extrapolationfrom the laboratory to the field.     

Fragmentation of Some Gliding Bacteria During the Growth Cycle

As similar relative size distributions were obtained when populations of gliding bacteria were studied with the light microscope or Coulter Counter, the latter was used to quantitate the fragmentation in Flexibacter sp. BH3 and Cytophaga sp. KM57. Both organisms fragmented in the late stationary phase of growth; both shrank rapidly in 0.9% (w/v) saline, and swelled on fixation in 2.5% (v/v) glutaraldehyde. Fixation in 0.025% (v/v) glutaraldehyde gave satisfactory preparations. The glucose concentration of the growth medium had little effect on motility, growth rate or size distribution, whereas an increase in the casamino acid concentration increased the duration of the exponential phase and the yield of cells but inhibited fragmentation and motility.     

The Pattern of Abortion of Developing Seeds in Lolium perenne L.

The pattern of seed abortion was followed in each floret offour centrally positioned spikelets in inflorescences of L.perenne from field plots given zero ( –F) or 150 kg Nh^–1 ( + F). There was severe lodging prior to anthesisin the +F plots and control inflorescences were compared withthose held in an erect position and with others reduced to fourcentral spikelets. In the - F plots there was only very limitedlodging and erect control inflorescences were compared withthose reduced to four central spikelets. Observations were madeover a 3-week period and the pattern of seed abortion was verysimilar in all of the treatments. Approximately half of thedeveloping seeds in each spikelet were lost by abortion andthere was a similar degree of loss from all florets. The numberof abortions increased greatly with time and approx. one-thirdwere of ovaries and two-thirds were of seeds at a very earlystage of development (1–2 mm in length and without chlorophyllformation). The effect of nitrogen fertilizer was to increaseboth the number of florets per spikelet and the mean weightper seed. The results are discussed in terms of the availabilityof resources to sustain seed development and growth; it is concludedthat the high degree of abortion may be due to genetic defectsassociated with outbreeding rather than with a shortage of nutritionalfactors