Seed Germination Responses of Field-Grown Dichanthelium Oligosanthes and Dichanthelium Sphaerocarpon to Chemical and Cold Stratification Treatments.

Dichanthelium, the rosette-grasses, are native and natural colonizers of roadside environments in southern New England, and may provide an alternative to introduced turfgrass species currently in use.  Species of Dichanthelium exhibit two distinct morphological flowering phases, the vernal phase (chasmogamous), which is open-pollinated, and the autumnal (cleistogamous), which is primarily closed-pollinated.  Plants of both Dichanthelium oligosanthes (Schultz.) Gould (few-flowered panicgrass) and D. sphaerocarpon (round-seeded panicgrass) were grown at the University of Rhode Island Crops Research Facility to produce seed for testing germination responses.  Seed collected in 2014 was subjected to cold treatment intervals of up to 12 weeks in conjunction with chemical treatments (captan fungicide, potassium-nitrate, sodium-nitroprusside or gibberillic acid).  Treatment containers were transferred to controlled-environment chambers for germination and data collected every 21 days.  Data were analyzed by chi-square.  While overall germination was low for all treatments (11.8-33.3%), significant (p < 0.01) increases in germination were observed following 6 weeks of stratification.   Chasmogamous seed of D. oligosanthes comprised the upper range of germination responses, and highly significant increases were observed following 3 weeks of chilling and continued to increase up to 7 weeks. Cleistogamous seed of D. sphaerocarpon also showed significant increases (p < 0.05) after 3 weeks, however, highly significant differences (p < 0.01) were observed following 6 weeks of chilling.  Pooling the data indicated that captan, potassium-nitrate, and sodium-nitroprusside increased germination of chasmogamous D. oligosanthes seed (p < 0.01), while gibberillic acid was shown to increase germination in cleistogamous D. sphaerocarpon seed (p < 0.01).  The data collected from chasmogamous seed of D. sphaerocarpon, and cleistogamous seed of D. oligosanthes, suggest that seed quality was suboptimal: likely due to premature collection or under-developed seed, water stress, or fungal colonization. Remaining seed from 2014 is being tested following the same methodology to confirm low viability.  Field-grown seed collected in 2015 will be tested and compared with wild-collected seed of the same species.