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Respiration of Dormant Seeds

1921; University of Chicago Press; Volume: 72; Issue: 1 Linguagem: Inglês

10.1086/332875

1940-1205

H. E. Sherman,

Seed and Plant Biochemistry

1. The respiratory intensity, that is, the mg. CO2 eliminated per gram imbibed seeds per hour, was determined experimentally for Amaranthus retroflexus, Chenopodium album, and Rumex crispus, as well as for Crataegus and certain drupaceous Rosaceae. Determinations of the catalase activity were also made for most of the seeds. 2. Catalase activity increases in Crataegus under after-ripening and germinating conditions (10⚬ C.), up to the forty-second day. The slightly higher value for the 128th day may represent: (1) a continued increase at an extremely slow rate; (2) a limit depending on the amount of dioxogen used (5 cc.); (3) a falling off, as a result of secondary dormancy, of an activity whose maximum occurred at the completion of after-ripening (about the ninetieth day). Respiration reaches a maximum intensity much earlier (sixth to eighth day), and thereafter exhibits a slow and fluctuating decline, at least to the seventy-seventh day. 3. In Amaranthus both catalase activity and respiration are relatively stable. Fluctuations in catalase activity and in respiratory intensity do not occur simultaneously, and may be in opposite directions. 4. The respiratory quotient and respiratory intensity vary markedly for different seeds, and in the Rosaceae for different lots of the same kind of seed under precisely similar experimental conditions. The respiratory quotient in Amaranthus and Chenopodium is markedly stable. Since in the Rosaceae the embryo is dormant, while in the other two seeds it is not, it may be that this difference in behavior is characteristic of seeds with dormant embryos, and the greater stability of respiration in Amaranthus and in Chenopodium represents the attainment of a more stable metabolism in these seeds. 5. Stability or variability of the quotient may be of significance as indicative of the possibility of an interplay of several factors on the metabolism. In Crataegus, and presumably in the other Rosaceae, the marked variability is probably the resultant between the respiration of the dormant hypocotyl and that of the mature cotyledons. 6. The arrangement of the respiratory quotients for each seed in a curve showing the percentages of the experiments with each seed giving each value, and in frequency histograms in which are plotted the actual number of experiments in which each quotient value occurred, indicates the tendency of each seed toward a typical respiration. The quotients for Chenopodium and Amaranthus are 0 928 and 0.856 respectively, while those of the Rosaceae form three groups within a range of 0 118. In the first group, between 0 648 and 0 7, fall the quotients for apricot, peach, and blue gage plum; in the third, between 0.8 and 0.876, those of cherry and sand-cherry; while that of hawthorn, 0 774, lies midway between.