問 題
次のＡ～Ｅはイモ類の挿絵である。イモ類に関する記述の内容及びそれと挿絵の組合せが最も妥当なのはどれか。ただし挿絵の縮尺は一様ではない。
1. Although the vast majority of the world is fed by wheat, corn, and rice, the Irish potato (Solanum melongena) ranks fifth following the sweet potato as a major food staple. Irish potato cultivation involves propagation by either seed or seed potatoes. Cultivation by seed potatoes is a method of asexual reproduction that produces plants genetically identical to the parent and maintains the desired traits within a cultivar. (Ａ)
2. Like the Irish potato, the sweet potato (Ipomoea batatas) is propagated vegetatively. Slips*1 , produced by the tuberous root in specially prepared beds, are transplanted into the field. In addition, sweet potatoes can also be propagated by vine cuttings. The carotene-rich root is an excellent source of vitamin A and is a good source of vitamin C. (Ｂ)
3. Taro (Colocasia esculenta) is believed to have originated in Southeast Asia and spread both east and west during prehistoric times. Today it is cultivated in the dry tropics, where it survives even in the drought years. Although not a major crop in the world market, taro remains locally important. The corms*2 of taro contain silica, which cause intense burning or stinging in the mouth and throat if eaten uncooked. (Ｃ)
4. Yams (Dioscorea spp.) are mainly tropical tuber crops, that are important staples in many areas of the world, especially West Africa, Southeast Asia, the Pacific Islands, and the Caribbean. Tubers of these bushes can vary from small ones the size of potatoes to massive ones often weighing over 40 kilograms. In many parts of Africa and Asia, yams are important in all aspects of the culture. (Ｄ)
5. Cassava (Manihot esculenta)is an important root crop in the subarctic region. Plants are propagated by seed potatoes that have axillary buds. It grows well in both arid and wet climates and produces storage roots in poor soil. Varieties are classified as either sweet or bitter, based on the concentration of tannins in the roots. (Ｅ)
*1 Adventitious shoots develop from the tuberous root.
*2 Modified underground stems found in monocots. Unlike bulbs, corms store food reserves in the stem, not in the leaves.
解 説
選択肢 1 ですが
A の挿絵はジャガイモです。主食として「・・・ ranks fifth (5位) following the sweet potato」に注目します。４位さつまいも、５位じゃがいもという文章ですが、ジャガイモの方が、主食として上位だろうと判断できると考えられます。よって、選択肢 1 は誤りです。
選択肢 2 ですが
B の挿絵はさつまいもです。妥当な記述です。
選択肢 3,4 ですが
C,D の挿絵と記述の対応が逆です。Cの挿絵はヤムイモで、Dの挿絵がタロイモです。
選択肢 5 ですが
キャッサバの特徴は茎を 25cm ぐらい切って地中に差すだけで育つという容易な栽培可能性です。 「seed potato」によるものではありません。よって、選択肢 5 は誤りです。
以上より、正解は 2 です。
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