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E rickson , R alph O. (U. Pennsylvania, Philadelphia.) Nomogram for the plastochron index. Amer. Jour. Bot. 47(5) : 350—351. Illus. 1960.–In an earlier paper, a plastochron index was described which specifies the development age of a shoot with some precision. The plastochron index of a shoot can be estimated quickly by use of the nomogram described here.
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Ralph O. Erickson (1960) studied this question.
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