BONINE, MARY L.* and LLOYD R. STARK. University of Nevada-Las Vegas, 4505 S. Maryland Parkway, Box 454004, Las Vegas, NV 89154-4004. - Growth and gametangial maturation in the desert moss, Syntrichia caninervis.
Populations of the desert moss, Syntrichia caninervis, were
sampled approximately every four weeks, and/or immediately following
significant hydration events at Red Rock National Conservation Area,
Las Vegas, Nevada, USA. Samples were collected from 12 populations (4
exclusively female, 4 mixed sex, and 4 exclusively male) over a period
of more than two years, from the fall of 1998 to the spring of 2001.
Collections were made using random coordinates on a grid to allow
mapping of population structure. During dissection, the presence of
distinct annual growth intervals permitted assessment of stem
elongation, quantification of gametangial initiation and maturation,
and determination of maturation indices for recent gametangia.
Sporophytes were initiated, but not matured, in both the spring of
1999 and 2000, and hence, we will not report on sporophytic
maturation. Stem elongation rates varied, apparently dependent on
microsite differences. Stems within the main portion of the cushion
elongated at approximately 0.3 mm per year, and stems on the edges of
the cushion or in the open elongated at less than 0.2 mm annually. On
average, growth intervals which contained gametangia consisted of
either a perichaetium with 4-5 archegonia or a perigonium with 14
antheridia. Archegonia were initiated in the fall of 1998 and became
receptive spring of 1999. Antheridia initiated at the same time
matured to half their full size by the end of spring, were dormant
during the summer of 1999, and did not disperse sperm until spring
2000. A few antheridia were completing maturation and dispersal of
sperm into spring 2001. Based on previous studies of desert moss
phenology, gametangial maturation, fertilization, and probably
sporophyte maturation occur during the cooler, moister fall through
spring months in the Mojave desert.
Key words: gametangial maturation, growth rate, phenology, Syntrichia caninervis