Factors influencing germination and seedling survival of several varieties of Astragalus lentiginosus dougl.


Category:  Range Science
Linked Publication
Language: English
Author(s): paul Ziemkiewicz
Description: Astragalus lentiginosus, which consists of 36 var ieties, is one of the principal locoweeds of western North America. The objectives of this study included identification of some of the major factors affecting germination of the seed and survival of the newly estab lished seedlings for several of these varieties. The seeds of the varieties studied exhibited two mechanisms for dormancy. One is a seed coat that is im permeable to water, and the other is a water-leachable inhibitor. The presence or absence of low-intensity incan descent light (in 14-hour daylengths) had no effect on germination. Of three temperature regimes studied, the regime 7/13 C proved optimal for both total and rapid rate of germination. However, though germinating at lower rates, weeds at -1/4 C and 21/27 C both ultimately reached high percentages of germination. Germination decreased linearly with increasing salinity to almost zero in NaCl solutions of -8.52 bars water potential. Variety araenosus, collected in a salt desert shrub vegetation type showed the highest germination at low temperatures and the greatest salinity tolerance. Seedling survival work was done with both pre-estab lished and established seedlings at the cotyledon to five leaflet stages of development. Seedlings were considered pre-established from the time of germination until the cotyledons were completely unfolded. Afterwards, the seed lings were considered established.