Removal of the pericarp and testa of seeds of japonica and indica rice (Oryza sativa) at various oxygen concentrations has opposite effects on germination

The germination of intact, dehusked, and peeled seeds (caryopses) of the japonica rice cultivar Sasanishiki, harvested 30, 40, 47 and 60 days after anthesis, and of the indica rice cultivar Assam IV, harvested 14 and 28 days after anthesis, was examined. Dehusking strongly inhibited germination of Sasanishiki seeds, with the exception that seeds harvested 30 days after anthesis gave minimal germination percentages even when left intact. Peeling (removal of the pericarp and testa) restored or enhanced germination, and 60–100% of seeds germinated after 10 days. By contrast, the rank order of germination of Assam IV seeds was intact, dehusked, and peeled seeds, with peeled seeds yielding germination percentages of 100%. In Sasanishiki, inhibition of germination of peeled seeds was observed at reduced oxygen concentrations (1–4% oxygen). This inhibition might explain the inhibitory effects of dehusking on germination of seeds from the japonica cultivar. It is possible that the testa and pericarp, which cover the embryos of dehusked seeds, acted as a barrier to the diffusion of oxygen to the embryo.     

Micropuncture pressure in small arteries or veins of perfused rabbit lungs

Until now, direct micropuncture measurements of vascular pressure in lung have been limited to small vessels less than 100 microns on the pleural surface. On the other hand, direct pressure measurements using small catheters (less than 1-mm OD) in pulmonary vessels have been limited to those greater than 1.2 mm. We measured pressure in intermediate-sized microvessels (300-700 microns) using the micropuncture method in isolated perfused rabbit lungs. These microvessels are located 2 or 3 mm beneath the pleura. We exposed them by microsurgery and punctured the relatively thick-walled vessels with specially configured micropipettes. We exposed one pulmonary microvessel in each rabbit lung by microsurgery on the left middle lobe. In 15 rabbit lungs we measured pressure in a total of six small arteries (275- to 470-microns diam) and nine small veins (300- to 700-microns diam) under high zone 3 conditions, near the zone 2/3 boundary. We found approximately 35% of the total pulmonary vascular pressure drop in arteries greater than 275-microns diam and 7% in veins greater than 300-microns diam. In veins greater than 500-microns diam, there was no measurable pressure drop. After the measurements, we froze the lung and confirmed that there was no detectable interstitial or alveolar edema in the cross sections of the punctured site. Our data are compatible with those of other investigators who have used isolated perfused rabbit lungs under similar experimental conditions.