ABSTRACT The southeastern United St...

ABSTRACT

The southeastern United States endemic plant species Trepocarpus aethusae (Apiaceae) behaves as a winter annual, with kernels germinating in autumn and bolting, flowering, and se production occurring the following growing season. Vernalization was not required for flowering, and plants flowered beneath both short and long days. Like germs of two other winter annuals in the Apiaceae, Chaerophyllum tainturieri and Ptilimnium nuttallii, those of T aethusae have underdevelop physiologically dormant beginnings and thus they have morphophysiological dormancy. Physiological dormancy was separated by warm stratification, and after it was stumbling embryo growth and germination occurr in 68-73% of the originals in light and in 52-65% of those in darkness at 15/6 20/10 and 25/15[degrees]C Unlike sperms of C. tainturieri and P nuttallii, which can re-enter physiological dormancy in autumn and experience annual dormancy/nondormancy cycles, only 1-12% of T aethusae originals re-entered physiological dormancy. However, T aethusae forms a long-lived persistent soil se bank; it for the most part is attributed to a delay in los of physiological dormancy and not to dormancy cycling. A comparison of dormancy-breaking and germination requirements does not reveal any reason wherefore C. tainturieri is more weedy than the other sum of two units species of Apiaceae. However, germs of C. tainturieri mature in late May-early June those of P nuttallii in mid to late June and those of T aethusae in mid to late August and early September. Thus, C tainturieri can vegetate in fields and on roadsides and consummated its life cycle before these habitats are disturbed according to human activities, but the other couple species could not complete their life round of years under these conditions.

INTRODUCTION

Chaerophyllum tainturieri curved catch Trepocarpus aethusae (Nutt.) ex DC and Ptilimnium nuttallii (DC) Britton are winter annual members of the Apiaceae, and they are restricted to eastern or southeastern United States (Gleason and Cronquist 1991) In these three species, grains germinate in autumn and plants dart flower, set seeds, and die the following growing season. Chaerophyllum tainturieri is institute in fields, along roadsides, and in other sites that may be disturbed annually, and thus it is considered to be a weedy species. However, T aethusae and P nuttallii spring up in habitats that are not disturbed by way of humans on an annual basis, and thus they are not considered to be weedy. What differences in (1) timing of life circle of time events such as flowering, se maturation, se dispersal and se germination, (2) environmental conditions required to break se dormancy and exalt germination, (3) environmental requirements for flowering, (4) air (or absence) of dormancy revolution of times in buried seeds, or (5) personality (or absence) of soil se banks help to explain wherefore one species is weedy and the other sum of two units are not weedy?

The dormancy-breaking and germination requirements as well as one information on the ecological life period are available for Chaerophyllum tainturieri (Baskin and Baskin 1990) and Ptilimnium nuttallii (Baskin et al. 1999); however, no of that kind studies have been done onward Trepocarpus aethusae. Thus, the meanings of our study were to (1) investigate various aspects of the ecological life period of T. aethusae, including phenology, vernalization and photoperiod requirements for flowering, and dormancy-breaking and germination requirements of seeds; and (2) compare the ecological life period of T. aethusae with that of C tainturieri and P nuttallii, with particular relation to seed dormancy and germination.

Trepocarpus aethusae is an annual that advances in margins of swampy forests and sandy river bottoms (Radford et al. 1968) in dried soil (Small 1933), at the brims of floodplain forests (Wilm and Taft 1998) and in wet sandy soil (Nelson 1993) The species has been reported from southern Carolina (Nelson 1993), Alabama, Mississippi, Louisiana, Texas, Oklahoma, Arkansas (Small 1933) Tennessee (Sharp and Baker 1964) Illinois (Wilm and Taft 1998) and Kentucky (Browne and Athey 1976) In the Land Between the Lakes in western Tennessee and western Kentucky T aethusae come into views on the sandy shores of Kentucky Lake in Stewart shire Tennessee, and in Trigg and Lyon counties, Kentucky (Chester 1986) The species is listed as rare in the Land Between the Lakes (Chester and Holt 1990) Georgia, and toward the south Carolina (Kartesz 1999) and as threatened in Kentucky (KSNPC 2000)

METHODS

Field Observations upon Life Cycle

Phenological observations were made upon several hundred plants of Trepocarpus aethusae growing in, and forward the edges of, mesic thickets dominated at Ulmus alata Michx., Gleditsia triacanthos L Disopyros virginiana L Acer negundo L A. saccharinum L Rubus argutus Link, and Vitis spp forward the east shore of Kentucky Reservoir at Fenton, Trigg shire Kentucky, within the Land Between the Lakes National Recreation Area (36[degrees]46'28''N latitude, 88[degrees]06'14''W longitude) at elevations of 109-115 masl. Observations were made from October 1991 [i]or[/i] part of to the other September 1992, with one or pair visits being made to the site each month Notes, photographs, and investigation specimens were taken during each visit. branch length was measured for several plants in the population at the time of each visit to determine their approximate average height; these values were cylindricaled to the nearest whole number.