Germination Ecophysiology of Eastern Deciduous Forest Herbs: Hydrophyllum macrophyllum

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Abstract
H. macrophyllum Nutt. (Hydrophyllaceae) is an herbaceous polycarpic perennial that occurs in mesic deciduous forests from western Virginia and West Virginia, to Illinois, and south to Georgia, Alabama and Arkansas [USA]. At the time of seed maturation and dispersal in mid- to late July, seeds exhibit both root and shoot dormancy. High temperatures are required to break root dormancy, and in the laboratory 77-85% of the seeds produced roots at a 12/12 h daily thermoperiod of 15/6.degree. C following a 2- to 4-wk warm treatment at a 12/12 h daily thermoperiod of 30/15.degree. C. In the natural habitat, root dormancy is broken during summer and early autumn and roots emerge from the seeds in late autumn. After root emergence, chilling is required to break shoot dormancy; 100% of the seeds (with emergent roots) produced shoots at 20/10.degree. C after they were chilled at 5.degree. C for 6 wk. In the natural habitat, shoot dormancy is broken during winter and shoots are produced in late winter and early spring. Germination of a portion of the seeds in a given year''s seed crop may be delayed for several years. Root emergence from seeds kept on soil under under leaf litter in an unheated greenhouse occurred during the 1st, 2nd and 3rd autumns following planting of freshly matured seeds.

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