Ethylene from alcohol lamps and natural gas burners: Effects on cotton ovules cultured in vitro

Summary In a transfer hood having positive pressure via flow of filtered air, momentary flaming of flask mouths via an alcohol lamp or natural gas burner introduced variable and often large amounts of ethylene into these culture vessels. Amounts of ethylene introduced depended upon where flask mouths were placed within the flame. Most ethylene diffused out of flasks within 2 hr if adequate fresh air exchange was provided, permitting cotton ovules to respond to hormones in ways reported in previous literature. However, it was concluded that flask-flaming could occasionally account for some variability in hormonal responses of cultured cotton ovules. Specifically, ethylene (assumed to be the most abundant and harmful substance admitted to the flasks via flaming) caused excessive ovular callus formation in combination with GA₃ and decreased the percentage of ovules forming fibers in response to IAA. This work was supported by the National Science Foundation Grant PCM 75-03944.     

Settlement Dynamics of the Encrusting Epibenthic Macrofauna in Two Creeks of the Caeté Mangrove Estuary (North Brazil)

The epibenthic encrusting fauna of 2 creeks of the Caeté mangrove estuary, northern Brazil, was studied over a 13 month period using collectors fixed at 2.5 and 3.5 m above the creek bottom and in which upper and lower sides of ceramic and wooden panels were used as settlement substrates. The number of individuals of the most abundant organisms (barnacles, oysters and mussels) settling per panel was determined each month, for each substrate type, panel orientation and height above creek bottom. The barnacle, Fistulobalanus citerosum has a peak settlement period during the wet season whereas both peaks in the numbers of settlers of the oyster Crassostrea rhizophorae were recorded during the dry season and such discrete temporal patterns in settlement have also been observed for barnacles and oysters in other mangroves and estuaries. In contrast to other studies, settlement of the mussel Mytella falcata was generally low during the study period and may be related to over-exploitation of stocks in the region. Overall, settler density was usually greater on the underside of ceramic panels close to the creek bottom, similar to results of other studies of epibenthic settlement in diverse habitats.     

Putting energy into mitochondrial protein import.

The import of proteins into mitochondria occurs in several steps. At least three of these steps require ATP and involve molecular chaperones. This energy requirement has served as a useful tool for elucidating the import pathways into the four mitochondrial compartments.     

Photokinesis of Macrobiotus hufelandi (Tardigrada, Eutardigrada)

Macrobiotus hufelandi Schultze, 1834 was tested for response to light. Size groups of less than 120 m and of 120 m or more were used. It was found that the smaller, younger size group exhibited a statistically significant negative response to light. This is hypothesized to function in conservation of body moisture and be more important to the smaller individuals because of the greater surface area-to-volume ratio. An experiment on response to gravity was done in an effort to determine if the negative photokinesis was the total result of a more complex type of behavior but this experiment did not detect any significant response to gravity in either of the size groups. Observation of the bacterial trails left by the tardigrades indicates that this behavior is not negative phototaxis, but rather negative photokinesis which is a non-directed, random movement in which the animal either increases its speed or changes its direction when exposed to light.