数種作物におけるクロロプラストの大きさ, 形および細胞壁に接する割合

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Comparative studies on size, shape and disposition of the chloroplasts located in the mesophyll cells were carried out with electron microscope in five cultivated species of Gramineae, viz. rice, barnyard millet, wheat, barley and corn, and in three cultivated Brassica species of Cruciferae, viz. B. campestris, B. oleracea and B. napus. Besides, the size and shape of the isolated chloroplasts as well as the isolated mesophyll cells were observed with light microscope. 1. The size (the area observed with microscope, S) of isolated mesophyll cells of rice was found to be the smallest among cereal crops studied. Compared to rice, the area (S) was 20 times more in wheat, 10 times in corn and 5 times in barnyard millet. The average size of mesophyll cells in Brassica species was the same as in barnyard millet. Among them, B. napus, a tetraploid species was observed to have larger mesophyll cells than diploid species, B. campestris and B. oleracea. The ratio of circumferential length to area of the mesophyll cell (l / S) was remarkably large in rice as compared with other species of Gramineae and Brassica species. 2. Light microscopy on the size of isolated chloroplasts showed that rice had the smallest chloroplasts among Gramineae, and that B. napus had the largest among Brassica species. In spite of the different sizes of chloroplasts in Gramineae and Brassica, the ratio of long and short diameter of the isolated chloroplasts was almost the same, about 1.4-1.5 in all species. 3. Electron microscopy revealed that the average ratio of long and short diameter of the chloroplasts located in the mesophyll cells was 3.25 in Gramineae and 3.20 in Brassic as pecies. The short diameter observed in this case was remarkably smaller than that observed on isolated chloroplasts with light microscope. It may be reasonable to infer that the chloroplasts existed in the mesophyll cells attaching their broad surface to the cell wall and that we observed the thickness of the chloroplast as short diameter in this case. 4. Electron microscopy revealed that the ploportion of the chloroplast surface contacted with the cell wall was around 43% (in a range of 40-47%), throughout the all species of cereals and Brassicas studied. This figure also suggests that the chloroplasts existed in the mesophyll cells attaching their broad surface to the cell wall. 5. The chloroplast surface contacted with the cell wall seems to be important as the site of gas exchange. If the proportion of the chloroplast surface contacted with the cell wall is almost equal throughout different species as observed above, the values of the chloroplast area index (CAI) defined by KARIYA and TSUNODA (1972, 73) may be important, not only from the view point of ligllt reception, but also from the view point of gas exchange.
日本作物学会の論文
1980-12-10

数種作物におけるクロロプラストの大きさ, 形および細胞壁に接する割合

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