Abstract.Earlier studies on the synthesis of C3-derived amino acids, plastidic isoprenoids and fatty acids from CO 2 by isolated chloroplasts in the light indicate the presence of a complete, but low-capacity, chloroplast (chip) 3-phosphoglycerate ~ acetyl-CoA pathway which is predominantely active in immature (developing) chloroplasts (A. Heintze et al., 1990, Plant Physiol. 93, 1121 1127. In this paper, we demonstrate the activity of the enzymes involved i.e. chip phosphoglycerate mutase, chip enolase, chlp pyruvate kinase and chip pyruvate-dehydrogenase complex (PDC), in the stroma of purified barley (Hordeum sativum L.) chloroplasts of different developmental stages. The chip phosphoglycerate mutase was partially purified for the first time. The activities of the enzymes of this chlp pathway (except PDC) were about a magnitude lower than those of the cytosolic enzymes. The chlp PDC of barley was more active than that of spinach. The apparent K m values of the enzymes of this pathway were about 100 IJM or lower except for the chip phosphoglycerate mutase which had a K m of 1.6-1.8 mM for 3-phospho-D-glycerate. Interestingly, no appreciable change in the activity of these enzymes was observed during maturation of the chloroplasts. In contrast, the activity of the reversible NADP +-glyceraldehyde 3-phosphate dehydrogenase increased about five times (from 140 to 590 nkat per g leaf dry weight). The following hypothesis is put forward to explain the regulation of carbon metabolism during chloroplast development: 3-phospho-D-glycerate is withdrawn from a common pool by the actions of 3-phosphoglycerate kinase and NADP +-glyceraldehyde-3-phosphate dehydrogenase, the activity of which increases considerably during matuDedicated to Prof. Dr. M.H. Zenk, Munich, on the occasion of his 60th birthday Abbreviations: C3 --* C2 pathway = 3-phospho-D-glycerate ~ acetylCoA pathway; Chl = chlorophyll; chip = chloroplast(ic); GAP = Dglyceraldehyde-3-phosphate; GAPDH = glyceraldehyde-3-phosphate dehydrogenase; PDC=pyruvate dehydrogenase complex; PEP = phosphoenolpyruvate; 2-and 3-PGA = 2-and 3-phospho-Dglycerate; U=unit; mmol.min ~(= 16.67 nkat)Correspondence to: G. Schultz; FAX: 49(511) 9 538584 ration of chloroplasts. This leads to an insufficient supply of 3-phospho-glycerate for the chip phosphoglycerate mutase, which has a low affinity for its substrate.

Since the abolition of beak trimming in laying hens in Germany, the importance of adequate enrichment material to help reduce feather pecking and cannibalism has grown. Here we tested an automatic enrichment device dosing grain via rough-coated pecking plates (PPs) on an organic farm, comparing its offer in four winter gardens (WGs). Winter garden (WG) 1 served as the control area without an automatic enrichment device, while WGs 2–4 offered different quantities of PPs, with WG 2 offering double the amount of PPs as WGs 3 and 4. The number of laying hens (Lohmann Brown Lite) per m² and close to the enrichment device (one hen‘s body length around) was determined using photo records. The usage behavior of the hens differed in the four WGs and with the animals’ age. Over the whole husbandry period (60 weeks), on average, 1.48 hens/m² were detected in the control area (WG 1), and a mean of 2.27 hens/m² in the enriched WGs. Compared to WG 1, the number of hens per m² was higher in WG 2 (2.43 hens/m²) and WG 3 (2.59 hens/m²) (p < 0.05), but similar in WG 4 (1.79 hens/m²). At the end of the husbandry period, fewer animals (mean of all WGs: 1.43 hens/m²) used the WGs than from beginning to the middle of the laying period (mean of all WGs: 2.05–2.15 hens/m²; p < 0.05). Our data indicate that the automatic enrichment device positively influences the animals’ use of the WG.

Feather pecking and cannibalism are prominent problems in modern laying hen husbandry. Among the various approaches to address this issue, environmental enrichment plays a crucial role. In this on-farm study, four winter gardens of an organic farm henhouse were equipped with an automatic enrichment device. Different quantities of downpipes dosing grain on rough-coated pecking plates (PPs) were tested. One group served as a control (CG) without an automatic enrichment device, while the others were offered different numbers of PPs, with one equipped with a doubled amount of PPs (DEG) compared to the other two groups (SEG). Video analyses of the hens’ duration of stay and behaviors in the recorded winter garden area and around the PPs were performed, and regular assessments of the plumage condition were conducted. By the end of the production cycle, no hens with intact plumage were found, with hens in the CG and DEG showing worse scores and earlier deterioration in the plumage condition than in the SEG. The offer of PPs showed a significant influence on the duration of stay in the filmed area. Hens in the DEG stayed significantly longer (mean: 129 s, SD: 126 s) than those in the CG (mean: 79 s, SD: 91 s; p < 0.05) and SEG (mean: 75 s, SD: 83 s; p < 0.005). On the performed behavioral bouts per hen and minute (CG mean bouts/minute (SD): 5.47 (2.92); SEG mean (SD): 5.33 (2.76); SEG mean (SD): 5.81 (3.24)), no significant influences were detected. Environmental pecking was the behavior most frequently observed in all winter gardens, where, particularly around the PPs, pecking at the device was observed. Therefore, the enrichment device can be assessed as well accepted by the hens in winter gardens. The effect of the device on the plumage condition remains unclear, with external factors probably showing a greater influence than the enrichment.