Cypripedium subtropicum (Orchidaceae) employs aphid colony mimicry to attract hoverfly (Syrphidae) pollinators.

In Orchidaceae, pollination is mostly animal-mediated, and one-third of species have evolved a deceptive pollination mechanism without rewards. Cypripedium is a representative lineage of nonrewarding orchids restricted to temperate regions. Cypripedium subtropicum flowers are pollinated by hoverflies and have hairy tufts that visually resemble an aphid colony covered with honey dew. We recorded the behavior of hoverflies on the flowers, determined the breeding system of the species and the structure of hairy tufts, and investigated the roles of hairy tufts and floral volatiles in this specialized pollination by using pollination experiments, scanning electron microscopy, bioassays and chemical analyses. The white hairy tufts covering the sidelobes of the labellum provide edible rewards and serve as crucial visual lures for hoverflies. The flowers emit primarily (E)-ß-farnesene and a smaller amount of ß-pinene that were found to attract hoverflies. Our results suggest that C. subtropicum uses both visual mimicry of an aphid-colonized labellum with a reward and chemical mimicry of aphid alarm pheromones to attract hoverflies for pollination. This is the first described example of a rewarding mimicry system in plants, where the models are animals with their secretions and the reward is similar in nutrients to that of the model mimicked.

Monitoring soil biological properties during the restoration of a phosphate mine under different tree species and plantation types.

Open-pit mining activities for minerals and metals have left an international legacy of highly polluted soils and degraded landscapes. Reforestation is usually supposed to restore soil fertility and ecosystem services, and therefore to remediate and recover polluted sites. However, our understanding of the effects of tree species and recovery time on the restoration of abiotic and biotic soil properties remains scarce. In this study, the effects of a series of restoration chronosequence (unrestored control, 10-year, 20-year, and natural forest) and plantation types (nitrogen-fixing broad-leaved Alnus nepalensis and coniferous Cupressus torulosa monocultures, as well as their mixed plantation) on soil physicochemical and biological properties were explored in a phosphate mine. Our results showed that soil quality index (SQI), which integrates important soil physical, chemical, and biological parameters including bulk density, soil organic carbon and microbial biomass, could provide valuable information about soil health. The average SQI values of 20-year plantations were 1.55 times of 10-year plantations, and the mixed plantation was 1.13 and 1.27 times of A. nepalensis and C. torulosa monoculture, respectively. Thus, recovery time, as well as plantation type, were the main determinants of the alterations in key soil conditions during the phosphate mining restoration. At the beginning restoration (10 years), A. nepalensis monoculture performed better than C. torulosa, providing an efficient restoration strategy for early revegetation. The mixed plantation of C. torulosa and A. nepalensis showed the higher moisture and soil organic carbon than did the monocultures, especially after 20 years of revegetation. Hence, our findings address a helpful guideline for selection of tree species and plantation practices, thereby aiding in long-term success of restoration.

Inflorescence and flower development in the Hedychieae (Zingiberaceae): Hedychium coccineum Smith.

The inflorescence of Hedychium coccineum Smith is thyrse, and the primary bracts are initiated in a spiral phyllotactic pattern on the sides of the inflorescence dome. Cincinnus primordia are initiated on the flank of the inflorescence apex, in the axils of primary bracts. This primordium subsequently develops a bract and a floral primordium. Then, the floral primordium enlarges, flattens apically, and becomes rounded. Sepals are initiated sequentially from the rounded corner of the primordium ring sepal initiation, and the floral primordium continues to enlarge and produces a ring primordium. Later, this ring primordium separates three common primordia surrounding a central cavity. The adaxial common primordium is the first separation. This primordium produces the posterior petal and the fertile stamen. The remaining two common primordia separate and produce respectively a petal and a petaloid, the inner androecial member. As the flower enlarges, the cavity of the floral cup becomes a rounded-triangular apex; these apices are the sites of outer androecial primordium initiation. The abaxial outer androecial member slightly forms before the two adaxial members develop. But this primordium ceases growth soon after initiation, while the two posterior primordia continue growth to produce the lateral petaloid staminodes. During this stage, gynoecial initiates in the floral cup and continues to grow until extending beyond the labellum.

The floral biology of Curcumorpha longiflora (Zingiberaceae): a ginger with two-day flowers.

Curcumorpha longiflora is a perennial chasmophyte (rock fissure plant) ginger that usually grows in crevices of calcareous rocks and forms patches on the understory of limestone monsoon rainforests. The pollination ecology of C. longiflora was studied by monitoring phenology and flowering behavior, observing pollinator activity (frequency and behavior of visitors), and the quantity and quality of pollination services. We also investigated the germination of pollen grains and growth of pollen tubes after different pollination treatments to detect its breeding system. Based on the results: (1) for the first time in Zingiberaceae a new protandrous mechanism was found with a two-day flowering to avoid autogamy in this species; (2) under field conditions, all individuals of C. longiflora usually produced only one flower every other day to keep geitonogamy to a minimum; (3) germination of pollen grains and growth rates of pollen tubes under different pollination treatments were the same 4 h later after pollination, suggesting that C. longiflora is completely self-compatible; (4) among the limited visitors, Bombus sp. and Apis florae were effective pollinators, but they were active at different times and at different stages of the flower, probably receiving different rewards.