Germination of Saccharum Ravennae (L.) L. Caryopses and Intact Spikelets.

Ravenna grass, Saccharum ravennae (L.) L. [Synonym Erianthus ravennae (Linn.) P. Beauv.], is a robust perennial bunchgrass grown as an ornamental in the United States, but where adapted has become naturalized.  Little is known about the seed size distribution and germination characteristics of Ravenna grass caryopses or intact spikelets.  Our objectives were to determine for two naturalized populations: 1) if molecular differences exist between populations; 2) the caryopsis size distribution; 3) the germination of sized caryopses; 4) the length of seedling shoots and roots from caryopses of different sizes; 5) the germination of unsized caryopses and intact spikelets; and 6) the length of seedling shoots and roots from unsized caryopses and intact spikelets.  Based on a DNA fingerprint, variation was found to exist between the two populations investigated.  Although seed production of Ravenna grass is relatively low, under favorable conditions it can produce more than 10,000 caryopses per panicle.  Caryopses germinated well within 14-d and averaged more than 80% germination.  Caryopses with a mass of 0.34 mg or more germinated exceeding of 90%.  Intact spikelets were slower to germinate in 14-d and had a lower percentage of abnormally germinated seed than caryopses.  Intact spikelets also had a significantly higher percentage of firm seeds compared with caryopses and the total potential germination of intact spikelets was greater than caryopses exceeding 90%.  Understanding the germination characteristics of Ravenna grass will aid in the development of seeding rates and the processing of seeds for agronomic uses.