Changes in the composition of cotton fibre cell walls during development

Purified cell walls, prepared from cotton fibres (Gossypium arboreum L.) at different growth stages, were subjected to successive extractions to give pectic, hemicellulosic, and agr-cellulosic fractions. The protein content and sugars obtained after hydrolysis of the total cell walls and of the various fractions were quantitatively estimated. The amount of protein in the fibre cell walls from one ovule reached a maximum value at the end of the elongation growth, decreased, and then reached a second maximum at the end of the secondary wall deposition. The absolute amounts of fucose, galactose, mannose, rhamnose, arabinose, uronic acid, and non-cellulosic glucose residues all reached a maximum at the end of the primary wall formation or at the beginning of the secondary wall formation. Only the absolute amounts of xylose and of the cellulosic glucose residues increased until the end of the fibre development. Most conspicuous was the decrease in the absolute amounts of non-cellulosic glucose and of arabinose residues during the secondary wall formation, possibly indicating a turnover of at least some of the hemicellulosic wall material

Radiometric Calibration Targets for the Mastcam-Z Camera on the Mars 2020 Rover Mission

The Mastcam-Z Camera is a stereoscopic, multispectral camera with zoom capability on NASA’s Mars-2020 Perseverance rover. The Mastcam-Z relies on a set of two deck-mounted radiometric calibration targets to validate camera performance and to provide an instantaneous estimate of local irradiance and allow conversion of image data to units of reflectance (R or I/F) on a tactical timescale. Here, we describe the heritage, design, and optical characterization of these targets and discuss their use during rover operations. The Mastcam-Z primary calibration target inherits features of camera calibration targets on the Mars Exploration Rovers, Phoenix and Mars Science Laboratory missions. This target will be regularly imaged during flight to accompany multispectral observations of the martian surface. The primary target consists of a gold-plated aluminum base, eight strong hollow-cylinder SmCo alloy permanent magnets mounted in the base, eight ceramic color and grayscale patches mounted over the magnets, four concentric, ceramic grayscale rings and a central aluminum shadow post (gnomon) painted with an IR-black paint. The magnets are expected to keep the central area of each patch relatively free of Martian aeolian dust. The Mastcam-Z secondary calibration target is a simple angled aluminum shelf carrying seven vertically mounted ceramic color and grayscale chips and seven identical, but horizontally mounted ceramic chips. The secondary target is intended to augment and validate the calibration-related information derived from the primary target. The Mastcam-Z radiometric calibration targets are critically important to achieving Mastcam-Z science objectives for spectroscopy and photometric properties.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737