The growth rate of rice coleoptiles is increased by low concentrations of ethylene, especially in oxygen concentrations lower than air; carbon dioxide enhanced this response. C2H4 is produced by rice seedlings, and this production is also enhanced by carbon dioxide. Ethane and propane were produced in trace amounts but were inactive in growth stimulation as were also methane, propylene, and butane.
A three-dimensional model with finite difference and time domain was established to investigate the enhancement of the light output intensity of GaN light-emitting diodes ͑LEDs͒ with bottom pillar ͑BP͒ structure. Through comparing the normalized light extraction intensity of GaN LEDs with or without BP in different dimensions, the theoretical results show that the light output intensity in the LED with BP structure involved could be enhanced by about 30%. The influence of BP structure on the light output intensity of a LED could be explained by the physical model of light interaction. In addition, the experimental results also show the same trend to the theoretical calculations.
Abstract. An improved method for isolating mitochondria from tomato fruit (Lycopersicon esculentum Mill.) is described. The fruit is chilled, and the tissue of the fruit wall cut by hand into very thin slices with a razor blade while immersed in a buffer containing 0.4 MI sucrose, 2 mm MgCl9, 8 mm EDTA, 4 mm cysteine, 10 mm KC1, 0.5 mg per ml bovine serum albumin 50 mm tris-HCI, pH 7.6. The pH is monitored and kept within the range of 7.0 to 7.2 by dropwise addition of 1 N KOH during cutting. The tissue is strained through 8 lavers of cheesecloth and centrifuged at 2000 X g for 15 minutes. The supernatant is then centrifuged at 11,000 X g for 20 minutess and the sediment is washed onoe with a medium oontaining 0.4 M sucrose, 10 mm KCI, 1 mm MgCl,,, 10 mm tris-HCl, 10 mmi KH9PO4 and bovine serum albumin (0.5 mg per ml), pH 7.2. Electron microscope studies show that this method gives homogeneous, relatively intaot mitochondria; they have a higher respiratory control ratio than those reported by other workers. The method was also tested successfully on fruits of cantaloupe and 'Honey Dew' melon.For further studies of fruit ripening and the role of ethylene, preparations of isolated mitochondria were desired which would have a high degree of respiratory control by ADP, good ADP/O values in accord with the generallv accepted limiting ratio, and a high degree of homogeneity with close resemblance between the fine structure of the isolated mitochondria and those in intact tissue sections. Various techniques for isolating mitochondria from fruits have been reported (3,7,12,14,21 sequent steps were carried out at this temperature. The chilled fruits were cut into 2 or more pieces, and the seeds and the highly acid gelatinous placental material were carefullv and completely removed. Portions of the outer and radial wall tissue (60 g) were immediately washed with buffer and immersed in buffer, where they were cut by hand into very thin slices with a stainless steel razor blade (fig 1). The buffer was based on one used by Lance et al. (14), consisting of 0.4 M sucrose, 4 mM cvsteine, 2 mm MgCl,, 10 mm KCl, 8 mm EDTA, 50 mM tris-HICl, and 0.5 mg per ml of BSA (bovine serum albumin, Fraction V, unesterified fatty acid poor) at pH 7.6. A pH range of 7.0 to 7.2 was maintained throughouit isolation with dropwise additions of 1 N KOH. The suspension was strained through 8 layers of cheesecloth, and the isolation procedure was completed as summarized in figure 1;
Some factors influencing dark respiration, photorespiration, and photosynthesis were examined for their effect on the CO2 compensation point (70 ,Ill) of detached soybean (Glycine max) leaf discs. A higher compensation point in young leaves decreased to the constant value after leaf expansion and maturation, but increased again during senescence.The compensation point was 40 to 50% higher in plants grown in the summer than in the winter. The compensation point and dark respiration increased with temperatures above 17 C. Below 17 C dark respiration continued to decrease, but the compensation point did not decrease further. Increasing light intensities did not affect the compensation point.The effect of selected chemicals on the compensation point were surveyed. Some buffer components did not greatly alter the compensation point but organic solvents lowered it. Potassium phosphate and pyrophosphate greaty increased it. Inhibitors of photosynthesis increased the compensation point. Hydroxypyridinemethanesulfonate and sodium bisufite severely inhibited photosynthesis in soybean leaves, stimulated dark respiration, and increased the compensation point.
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