Germination de Sedum oxypetallum (Crassulaceae) in a primary lava-field shrubland

Sedum oxypetalum is one of the dominant species in the xerophilous shrublands in the lava fields of the Basin of Mexico. Germination of this species was evaluated to understand its ecological response. We tested the effects of different pre-germination treatments (cold, and dry and wet heat) and storage time, as well as those of natural priming in two microhabitats with different disturbance levels. Experiments were performed in laboratory conditions under constant (25 °C) and fluctuating (20/30 °C) temperatures. Seeds did not germinate during burial and proved to be positively photoblastic. Under pre-germination treatments, final germination percentage was higher at 20/30 °C in seeds after four or more months of storage. None of the pre-germination treatments favored germination. Seeds can survive for more than 1 year and form a seed bank. Thus, seeds underwent natural priming that favored final germination percentage; however, germination rate and lag time were not affected by this process. In natural conditions, germination is delayed until the rainy season, improving the success of seedling establishment and growth. We discuss the role of fluctuating temperature in germination processes and the adaptations of seeds to their seasonal environment

Natural priming of Wigandia urens seeds during burial: effects on germination, growth and protein expression

To determine whether seeds of the weedy shrub Wigandia urens, from the Valley of Mexico, undergo natural priming when buried in soil, comparative experiments were performed with seeds: (1) harvested directly from the plant

Effect of environmental heterogeneity on field germination of Opuntia tomentosa (Cactaceae, Opuntioideae) seeds

We studied in Opuntia tomentosa the effect of plant shade (orientation and distance), and the place where the seeds remained before germination. Seeds were collected in 1998 and a) sown immediately on soil (non-buried seeds), b) stored in the laboratory and sown on soil during the 1999 rainy season (control) or c) buried after collection (under the shade of a tree, a rock and in an open space), exhumed 7 months later and sown in 1999 (exhumed seeds). Seeds were sown under or outside the shade of several trees: or on the northern, eastern and western sides of a 14-m-tall tree. In 1999, germination was high in all samples, but the control seeds had delayed germination. After two rainy seasons, non-buried seeds had the lowest germination rate. Germination was not affected by the distance from the tree. Outside of the plant's shade, germination was low. Germination was affected more by the environmental heterogeneity than by the individual plant shade. Germination probabilities were the highest at 16-19 degrees