ABSTRACT. The bathymetric distribution, biomass, growth dynamics and production of surfgrass species in Baja CaMornia (NW Mexico) were examined. The maximum cover of Phyllospad~x scouleri (16 + 3.6%) was found between 40 dnd 50 cm below MLWL (mean low water level), whereas P. torreyi showed continuous cover (100%) at the lower intertidal (80 to 90 cm below MLWL). Both species showed sllnilar seasonal patterns, with the lowest rate of production of new leaves and biomass observed in April, when the dayt~me exposure to air of the ~ntertidal area studied was longest The production of surfgrass wa.s very high, exceeding 8000 g DW m-' yr.', and the rhizome elongation rate ranged from 0.24 to 0.58 mm d-l, resulting in an annual rhizome growth rate of about 8.6 cm yr-' The growth and biomass of both species tended to decline with increasing exposurp to air during day hours, but this decline was strongest for P. torreyi. The leaves of P torreyi desiccated faster than those of P. scouleri when exposed to air, and the net photosynthesis rate of P. torreyi was more affected than that of P. scoulen after being exposed to air for simllar lengths of thme. The shoot size of P, torreyi was more affected than that of P. scoulen under the same regime of air exposure. These results suggest that P. torreyi is more sensitive to desiccation than P scouleri, and point to both species as the most productive seagrass communities yet studied.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 138.251.14.35 on Tue, 26 May 2015 22:50:49 UTC All use subject to JSTOR Terms and Conditions THE SOUTHWESTERN NATURALIST 33(2):167-175 JUNE 15, 1988 VEGETACION Y FLORA ACUATICA DEL LAGO DE PATZCUARO, MICHOACAN, MEXICO. ANTONIO LOT Y ALEJANDRO NOVELO RESUMEN-La flora del Lago de Paitzcuaro, Michoacin, Mixico, constituida por 34 gineros, 48especies pertenecientes a 22 familias de plantas vasculares es notable por su riqueza en comparaci6n con otros sistemas acuiticos mexicanos. Se distinguen las afinidades floristicas de los taxa presentes y se examinan someramente sus asociaciones bajo 4 grandes unidades de vegetaci6n, cartografiadas en un mapa.ABSTRACT-The flora of Lake Patzcuaro, Michoacan, Mexico, has 48 species in 22 families of vascular plants. In comparison with other aquatic systems of Mexico, this one is especially rich in species. The floristic affinities of the taxa are presented. Four major vegetation associations are described and a map with their distributions is provided.
1 2Three field surveys and an extensive review of surfgrass (Phyllospadix) 3 specimens from herbarium collections in USA and Mexico were performed to delimit the 4 geographical distribution of Phyllospadix scouleri and Phyllospadix torreyi along the 5 coasts of Baja California (Mexico) which showed that both species had the same 6 distribution in the peninsula with a southern limit at 24º 31' N. Cover estimates along 3 -7 8 transects laid in the lower intertidal and upper subtidal of three locations in Baja 8California indicated that P. scouleri occurs shallower than P. torreyi when coexisting. A 9 preliminary, short-term experimental increase of nutrient availability in the water column 10 at one of the study sites suggested that the biomass and growth rates of P. torreyi were 11 more limited by the availability of nutrients than those of P. scouleri. 12 13
RESUMENSe presenta la revisión de la información sobre la riqueza y distribución de las monocotiledóneas acuáticas y subacuáticas (herbáceas) de México, con el fin de contribuir al mejor conocimiento de la flora de los humedales distribuidos en el territorio nacional. Se registraron 381 especies (392 taxa) pertenecientes a 104 géneros y 28 familias, referentes a las categorías de acuáticas estrictas y subacuáticas. Adicionalmente se documentaron 114 hidrófitas tolerantes o facultativas del hábitat palustre y lacustre. La mitad de las familias corresponden a taxa que la mayoría de los botánicos ubicarían como terrestres, pero con una representación significativa en el conjunto de plantas acuáticas mexicanas (71% de géneros y 75% de especies). El elemento endémico representa 14% del total de las monocotiledóneas. Su existencia en una gran variedad de hábitats y la representación en numerosos tipos de vegetación y comunidades, las colocan entre los elementos ecológicos y geográficos más diversos en el continente americano. En lo referente a las afinidades geográficas, encontramos que el componente meridional (46%) supera por casi el doble al boreal (25%), mientras que el elemento mexicano (13.9%) es equivalente a la suma del cosmopolita y de las especies introducidas.Palabras clave: distribución geográfica, hidrófitas, monocotiledóneas mexicanas, riqueza florística. ABSTRACTA review of the information on the richness and distribution of the Mexican aquatic and wetland (herbaceous) monocots, is presented, for the purpose of contributing to a
Estudio morfológico de diásporas de algunas especies de plantas acuáticas del Valle de México 1 MARIBA ÜLVERA y ANTONIO LOT 2 RESUMEN. Se describe la morfología externa e interna de las diásporas de veintidos especies pertenecientes a doce familias de plantas acuáticas estrictas del Valle de México. Las características externas muestran gran variación a nivel de familia, mientras que en los truca cercanamente relacionados se observa un patrón morfológico similar, y tanto la cubierta seminal como la superficie del pericarpo son de mayor valor taxonómico; la morfología interna de las semillas es muy semejante entre los truca emparentados filogenéticamente. Se encontraron semillas albuminosas y exalbuminosas con dos tipos de embriones: amplio y linear, siendo este último el más común. El material de reserva de todas las semillas es almidón. ABSTRACT. Externa! and interna! morphology of diaspores of twenty two species of twelve families of aquatic plants of Valley of Mexico are described. Externa! study of the seeds show remarkable variations among the families, while those truca nearly related exhibit a similar morphological pattern. The seed coat and the surface of the pericarp show a high truconomic value. The interna! features of the seed are ve!)' similar within related truca. There are two kinds of seed: 1) albuminous and 2) exalbuminous, and two embl)'O types, broad and linear; the linear embl)'O is more common among species. Starch is the food reserve in ali seeds.En general la información sobre la morfología de las diásporas de plantas vasculares acuáticas se encuentra en floras y revisiones taxonómicas, en las cuales frecuentemente son tratadas superficialmente. La morfología detallada de las diásporas proporciona descripciones útiles en las delimitaciones taxonómicas, sobre todo en las especies que 1 Este trabajo representa una parte de la tesis de licenciatura presentada en 1988 por la primera autora en la Facultad de Ciencias, Universidad Nacional Autónoma de México.
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