Thermopsis

Abstract: The paper gives the chromosome numbers of 45 species from 72 Mongolian localities, belonging to the genera:Amygdalus, Asparagus, Astragalus, Cancrinia, Caragana, Chamaerhodos, Chelidonium, Chesneya, Dianthus, Hypecoum, Lathyrus, Lilium, Oxytropis, Papaver, Potentilla, Schizonepeta, Sibbaldia, Thermopsis, Trifolium, Trigonella, Vicia. Chromosome morphology of three species ofChamaerhodos and taxonomical remarks on some other species are added. A new combinationSibbaldia sericea (Grubov) Sojak is proposed.

Abstract: Light harvesting and utilization by chloroplasts located near the adaxial vs the abaxial surface of sun and shade leaves were examined by fluorometry in two herbaceous perennials that differed in their anatomy and leaf inclination. Leaves of Thermopsis montana had well-developed palisade and spongy mesophyll whereas the photosynthetic tissue of Smilacina stellata consisted of spongy mesophyll only. Leaf orientation depended upon the irradiance during leaf development. When grown under low-light levels, leaves of S. stellata and T. montana were nearly horizontal, whereas under high-light levels, S. stellata leaves and T. montana leaves were inclined 60° and 30°, respectively. Leaf inclination increased the amount of light that was intercepted by the lower leaf surfaces and affected the photosynthetic properties of the chloroplasts located near the abaxial leaf surface. The slowest rates of quinone pool reduction and reoxidation were found in chloroplasts located near the adaxial leaf surface of T. montana plants grown under high light, indicating large quinone pools in these chloroplasts. Chloroplasts near the abaxial surface of low-light leaves had lower light utilization capacities as shown by photochemical quenching measurements. The amount of photosystem II (PSII) down regulation, measured from each leaf surface, was also found to be influenced by irradiance and leaf inclination. The greatest difference between down regulation monitored from the adaxial vs abaxial surfaces was found in plants with horizontal leaves. Different energy dissipation mechanisms may be employed by the two species. Values for down regulation in S. stellata were 2-3 times higher than those in T. montana, while the portion of the PSII population which was found to be Q B nonreducing was 4-6 times lower in high light S. stellata leaves than in T. montana. All values of Stern-Volmer type nonphotochemical quenching (NPQ) from S. stellata leaves were similar when quenching analysis was performed at actinic irradiances that were higher than the irradiance to which the leaf surface was exposed during growth. In contrast, with T. montana, NPQ values from the abaxial leaf surface were up to 45% higher than those from the adaxial leaf surface regardless of growth conditions. The observed differences in chloroplast properties between species and between the adaxial and abaxial leaf surfaces may depend upon a complex interaction among light, leaf anatomy and leaf inclination.

Abstract: -Demography of the rare perennial herb Santa Ynez thermopsis (Thermopsis macrophylla var. agnina) was monitored at two sites for 9 yr after a controlled burn in the Santa Ynez Mountains near Santa Barbara, California. One of the burned sites was located in chaparral and the other in a fuelbreak, an area purposely cleared of chaparral to slow the advance of wildfire. Numerous individuals resprouted in the 1st yr after the fire and thousands of seedlings established from heat-stimulated germination of refractory seed. Vegetation before and after the fire was markedly different between the two sites. Despite this difference, however, seedling production was very similar on the two sites. Losses of recruits-seedlings that survived beyond the 1st yr-also were similar. Nine yr after the fire the density of recruits was equivalent on both sites. Recruits were significantly taller in the fuelbreak than in the chaparral but the average number of stems/individual was not different. Individuals that resprouted after the fire produced more than 106 seeds/900 m2 from 1980-1987. However, only 3.9% of the seed was present in the soil 8 yr after the fire. Seed production by recruits, in contrast, was very low and appeared to be declining. Thus, this species relies heavily on seed production by resprouts to maintain a sizable soil-seed bank. In addition to seed production by resprouts, the survival of recruits during the interfire period is a critical life history stage in the population biology of this species. Recruits that survive both the interfire period and the next fire show marked increases in stem production, seed output and survivorship.

Abstract: Comprehensive reevaluation of both herbarium specimens and field observations of the North American Thermopsis leads to our recognition of 10 species. Three species occur in the southern Appalachians: T. villosa, T. mollis, and T fraxinifolia. The Rocky Mountains and intermountain regions are populated by the relatively variable and widespread species T. divaricarpa, T. montana, and T rhombifolia. The Pacific coastal mountains of California are dominated by the variable T californica (with three infraspecific taxa), which gives way to T gracilis in northern California and western Oregon. Thermopsis macrophylla and T robusta have restricted ranges in California.