CO2, light and temperature influence senescence and protein degradation in wheat leaf segments

Effects of environmental conditions influencing photosynthesis and photorespiration on senescence and net protein degradation were investigated in segments from the first leaf of young wheat (Triticum aestivum L. cv. Arina) plants. The segments were floated on H2O at 25, 30 or 35°C in continuous light (PAR: 50 or 150 µmol m−2 s−1) in ambient air and in CO2-depleted air. Stromal enzymes, including phosphoglycolate phosphatase, glutamine synthetase, ferredoxin-dependent glutamate synthase, phosphoribulokinase, and the peroxisomal enzyme, glycolate oxidase, were detected by SDS-PAGE followed by immunoblotting with specific antibodies. In general, the net degradation of proteins and chlorophylls was delayed in CO2-depleted air. However, little effect of CO2 on protein degradation was observed at 25°C under the lower level of irradiance. The senescence retardation by the removal of CO2 was most pronounced at 30°C and at the higher irradiance. The stromal enzymes declined in a coordinated manner. Immunoreactive fragments from the degraded polypeptides were in most cases not detectable. However, an insolubilized fragment of glycolate oxidase accumulated in vivo, especially at 25°C in the presence of CO2. Detection of this fragment was minimal after incubation at 30°C and completely absent on blots from segments kept at 35°C. In CO2-depleted air, the fragment was only weakly detectable after incubation at 25°C. The results from these investigations indicate that environmental conditions that influence photosynthesis may interfere with senescence and protein catabolism in wheat leaves.

An Exploration Based Cognitive Bias Test for Mice: Effects of Handling Method and Stereotypic Behaviour

Behavioural tests to assess affective states are widely used in human research and have recently been extended to animals. These tests assume that affective state influences cognitive processing, and that animals in a negative affective state interpret ambiguous information as expecting a negative outcome (displaying a negative cognitive bias). Most of these tests however, require long discrimination training. The aim of the study was to validate an exploration based cognitive bias test, using two different handling methods, as previous studies have shown that standard tail handling of mice increases physiological and behavioural measures of anxiety compared to cupped handling. Therefore, we hypothesised that tail handled mice would display a negative cognitive bias. We handled 28 female CD-1 mice for 16 weeks using either tail handling or cupped handling. The mice were then trained in an eight arm radial maze, where two adjacent arms predicted a positive outcome (darkness and food), while the two opposite arms predicted a negative outcome (no food, white noise and light). After six days of training, the mice were also given access to the four previously unavailable intermediate ambiguous arms of the radial maze and tested for cognitive bias. We were unable to validate this test, as mice from both handling groups displayed a similar pattern of exploration. Furthermore, we examined whether maze exploration is affected by the expression of stereotypic behaviour in the home cage. Mice with higher levels of stereotypic behaviour spent more time in positive arms and avoided ambiguous arms, displaying a negative cognitive bias. While this test needs further validation, our results indicate that it may allow the assessment of affective state in mice with minimal training— a major confound in current cognitive bias paradigms.

Effects of variation in nest curtain design on pre-laying behaviour of domestic hens

Laying hens in loose-housing systems select a nest daily in which to lay their eggs among many identical looking nests, they often prefer corner nests. We investigated whether heterogeneity in nest curtain appearance – via colours and symbols – would influence nest selection and result in an even distribution of eggs among nests. We studied pre-laying behaviour in groups of 30 LSL hens across two consecutive trials with eight groups per trial. Half of the groups had access to six identical rollaway group-nests, while the others had access to six nests of the same type differing in outer appearance. Three colours (red, green, yellow) and three black symbols (cross, circle, rectangle) were used to create three different nest curtain designs per pen. Nest position and the side of entrance to the pens were changed at 28 and 30 weeks of age, respectively, whereby the order of changes was counterbalanced across trials. Nest positions were numbered 1–6, with nest position 1 representing the nest closest to the pen entrance. Eggs were counted per nest daily from week of age 18 to 33. Nest visits were recorded individually with an RFID system for the first 5 h of light throughout weeks 24–33. Hens with access to nests differing in curtain appearance entered fewer nests daily than hens with identical nests throughout the study but both groups entered more nests with increasing age. We found no other evidence that curtain appearance affected nest choice and hens were inconsistent in their daily nest selection. A high proportion of eggs were laid in corner nests especially during the first three weeks of lay. The number of visits per egg depended upon nest position and age: it increased with age and was higher after the nest position change than before in nest position 1, whereas it stayed stable over time in nest position 6. At 24 weeks of age, gregarious nest visits (hens visiting an occupied nest when there was at least one unoccupied nest) and solitary nest visits (hens visiting an unoccupied nest when there was at least one occupied nest) accounted for a similar amount of nest visits, however, after the door switch, gregarious nest visits made up more than half of all nest visits, while the number of solitary nest visits had decreased. The visual cues were too subtle or inadequate for hens to develop individual preferences while nest position, entrance side, age and nest occupancy affected the quantity and type of nest visits.

Nest choice in laying hens: Effects of nest partitions and social status.

Nest choice in loose-housed laying hens is influenced by nest characteristics, position and social factors. We examined the relative preference of laying hens for two group-nests differing in the presence or absence of a partition in the middle of the nest and whether this was influenced by social status. We hypothesized that hens would prefer the partitioned nest as it provides more enclosure, and that social status would affect nest choice. Relative preference for the nests was assessed in a free choice preference test conducted in two consecutive trials each with eight groups of 20 hens from 18 to 31 weeks of age. The hens were individually marked and had access to two commercial group-nests (49 × 114 cm), one of which contained an internal wooden partition (30 × 10 cm) which divided the nest in two halves. At 28 weeks of age, the position of the nests was switched. The number of eggs laid was recorded daily. On one day each at 24 and 28 weeks of age (after the nest switch) video recordings were made of the first 5 h of daylight. From these videos we recorded the number of nest visits per egg per nest and the number of nest visits for individual hens. On one day each at 24 and 27 weeks of age we also recorded videos from within the nests to assess individual nest choice for egg-laying. In addition, we recorded aggressive interactions between individual hens during the first hour of light on one day each at 18, 24 and 27 weeks of age to establish social status. We found a relative preference for the partition nest with a greater proportion of eggs laid in these nests as well as fewer nest visits per egg. The hens were also consistent in their egg-laying location over the two days of observation. After the nest switch, however, the hens did not switch egg laying location and the number of visits per egg no longer differed between nests suggesting that the preference for the partitioned nest was only important at the beginning of lay. In addition, although social rank had no impact on preference of nest type, lower ranking hens performed more nest visits and laid their eggs slightly later on the second observation day (week 27 of age) compared with higher ranking hens. Therefore, the use of partitions could improve the attractiveness of group-nests.