| Saussurea involucrata (Kar. et Kir.) Sch.-Bip is an herbaceous monocarpic perennial alpine plant that lives more than 5 years. It is one of the traditional Chinese medicinal plants and belongs to the grade III protected plant. In this paper, its reproductive characteristics, including floral morphology, breeding system, pollination ecology, fruit-set patterns and seed (fruit) germination were analyzed in field and laboratory. The main results are as follows:1) Temperature and relative humidity outside of the bracts were significantly lower than they were inside of the bracts. The maximum differences were 7.2℃and 54.2%, respectively, at 1400 h (solar time); mean differences were 0.6℃and 12.8 %, respectively. All florets within the compound capitula are tubuliflorous. There are about 22 individual capitula in a compound capitulum and about 120 purple flowers in each individual capitulum. Diameter of a compound capitulum is 8-10cm. The longevity of a floret, i.e. from corolla opening to wilted stigma, is 4-6 d. Within a capitulum, time from first floret opening to last floret wilted is 20-25 d. Floret opening for a single plant lasted about 45-55d, and for the whole population about 65-75d. During each flowering season, May to September, favorable temperature and precipitation provided good conditions for S. involucrata to complete reproduction.2) Within all capitula, peripheral florets open first, and then the central ones open. Within the compound capitulum, the first floret to open is in the central capitulum, and then a floret in the peripheral capitulum opens. For a floret, there was a conspicuous difference in growth rate between anther tube and style. In the functionally male phase of anthesis, from the flower bud stage to unopened stigma lobes, the whitish style gradually emergence from the anther tube with whitish pollen grains on its tip, and this was accompanied by opening of the corolla lobes. Abundant pollen grains adhere to the outer surface of the stigma at the same time that the inner surfaces are still tightly pressed together. In the functionally female phase of anthesis, the stigma lobes are clearly separated and thus the glabrous inner surfaces are exposed.3) Out-crossing index (OCI) and pollen to ovule ratio (P/O) values for S. involucrata were 5 and 27375±5480, respectively, indicating that this species is xenogamous and thus requires pollinators for seed set. However, bagging and artificial pollination experiments indicated that this species is self-compatible but that reproductive success of allogamy (both between different flowers on the same plant and different flowers on different plants) is significantly higher than that of autogamy. Cross-fertilization by herkogamy and by protandry in S. involucrata may enhance chances of allogamy and gene flow among individuals or florets and thus retain the advantages of cross-pollination under the severe alpine environment of Tianshan Mountain.4) Saussurea involucrata has a pleasant odor that is especially strong during reproductive growth. Both nectar volume and sugar concentration of a single floret reached maximum value at 1200 h (solar time). Over a 3-day period of consecutive nectar secretion, nectar volume gradually increased, while sugar concentration decreased. The florets were visited by insects in orders Hymenoptera, Diptera, Hemiptera and Lepidoptera during the short flowering phase. Hymenoptera, particularly Bombus spp. (including B. paradoxus, B. lucorum and B. glacialis) are the most important pollinators because of their number and diversity. Other diurnal pollinators, such as Calliphora uralensis, Pontia callidice, Clossiana euphrosane and Aglais urticae also visit this species. Visitor activity began at 0700 h, reached a maximum at about 1000 h and ended at 2100 h. From 0900 h to 1900 h, visitor frequency per plant and per capitulum lasted about 10 hours. Length of time per landing spend on a capitulum gradually increased from 1100 to 1400 h and then declined until 2100 h.5) Number of florets, number of seeds and percentage seed set within the central capitulum of compound capitula were 62±15, 56±11 and 90±6, respectively. On the other hand, number of florets, number of seed and percentage seed set of the peripheral capitulum were 132±23, 123±22 and 93±4, respectively. There were significantly differences in floret number, seed number and seed set between central and peripheral capitula; these differences may be due to pattern of resource reallocation.6) Morphological characteristics of fruits and dispersal mode of S. involucrata were investigated. Fruits with long pappus (cypsela) have a single seed that develops from an anatropous ovule. The mature columnar achene is brown and 6±1mm long×1±1mm wide, and it weighs 2.35 mg. It has a plumose pappus and is dispersed by wind or water.7) Rate and percentages of germination reached maximum values at 25℃. Under laboratory storage conditions, seed germination of peripheral and central capitula at alternating temperatures in constant darkness after 5 days on wet filter paper were 88±1% and 70±1%, respectively. Germination of Seeds from different positions in peripheral and central capitula at alternating temperatures in light/dark (12 h/12 h) after 5 days on wet filter paper were 43±1% and 36±2%, respectively. In all treatments, cold stratified (4℃) seeds germinated to 100% after 5 days. Seeds are light sensitive, germinating to high percentages in dark but low percentage in light/dark. Based on the fact that dormacy was broken by a short period of cold stratification (4 weeks), we conclude that S. involucrata has non-deep physiological dormancy (PD). Further evidence that S. involucrata likely has non-deep PD are the facts that members of the Asteraceae have fully developed embryos and water permeable fruit/seed coats. These three characteristics define non-deep PD.
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