Spike Inflorescence Research Articles

Spikelet and Floret Naming Scheme for Grasses with a Spike Inflorescence

Effective schemes to name uniquely and define parts of grass plants allow researchers to communicate results of their experiments accurately and precisely. Naming schemes for vegetative parts of grass plants have been developed; however, no system exists to name uniquely parts of the inflorescence. In this report, we present a method to extend existing systems to name parts of grass spikes. Spikelet positions are denoted by the letter S and numbered acropetally along the rachis. For example, the third spikelet position from the base of the rachis is named S3. Likewise, floret positions along the rachilla are named F (or C after fertilization) and numbered acropetally from the base to tip. The second caryopsis (floret) in the spikelet at the third spikelet position on a spike would be named S3C2. This simple scheme, when combined with the system for naming tiller, leaves, and roots, will allow all plant parts to be named uniquely. If the caryopsis in the previous example was produced on the tiller formed in the axil of the first leaf on the main stem, the complete description of the caryopsis is T1S3C2. Using this system, researchers and practitioners can communicate precisely findings on development, growth, and functional characteristics of plants and plant parts.

Unicarpellate floral development in Potamogeton zosteriformis

Floral development in the species Potamogeton zosteriformis is compared with that of other species of Potamogeton previously investigated (P. densus and P. richardsonii). A spike inflorescence is found on which 6 to 20 flowers develop. These flowers develop their appendages acropetally; first, the four tepals are initiated followed by the four stamens opposite the tepals. As in the flower of P. densus, the two lateral stamens are each initiated as two separate primordia. Unlike any other Potamogeton species where four carpels generally arise, alternating with the tepal and stamen pairs, in P. zosteriformis a single carpel consistently develops on the central portion of the remaining floral meristem. Histological preparations did not reveal any vestigial procambial strands differentiating in the gynoecium. This unique floral development is examined from several points of view. Morphogenetic comparisons are made with other species of Potamogeton which develop tetramerous gynoecia. Morphologically the nature of the Potamogeton flower is reexamined and phylogenetically the possibility of P. zosteriformis as a link or transition between the bisexual and unisexual groups within the Najadales is considered.