Bijoy Neog

Pollination biology of Disanthus cercidifolius var. longipes, an endemic and endangered plant in China

Disanthus cercidifolius Maxim. var. longipes H.T. Chang usually has two inflorescences growing in opposite directions in the axillae, but occasionally three inflorescences grow paratactically. The typical flowering process could be divided into 4 periods: “Pre-dehiscence”, “Initial dehiscence”, “Full dehiscence” and “Withering”. Both the natural population and the planted population had a flowering peak of 15–35 days after the first flower bloomed. There were significant differences between the time courses of flowering of the two populations. Out-crossing is the main breeding system in this species. And autogamy decreases the risk of reproductive failure of this species. The main insect pollinators of D. cercidifolius var. longipes are Episyrphus balteatus de Geer, Scaptodrosophila coracina Kikkawa and Peng, Polistes olivaceus de Geer, Apis cerana Fabricius, Nezara viridula L. and Coccinella septempunctata L., and so on. Among the insects, S. coracina and E. balteatus are the most important and efficient pollinators, but others are inefficient pollinators. Though wind pollination is not efficient, it guarantees reproduction when insect pollinators are not available. “Mass flowering” is an adaptive behavior and reproductive strategy of this species, and “few fruiting” could be caused by the lack of pollinators.

Effects of AM Fungi and Plant Growth-promoting Rhizobacteria on Enzymatic Activities of Soil under Turmeric (Curcuma longa L.) Cultivation

Rhizomes of turmeric (Curcuma longa L.) are widely used for their medicinal as well as flavoring properties and in order to concentrate on biological means of promoting turmeric cultivation in Assam, a greenhouse experiment was conducted to evaluate the effects of native arbuscular mycorrhizal fungi (Glomus, Gigaspora and Acaulospora sp.) sourced from turmeric rhizosphere along with phosphate solubilizers (Bacillus megaterium) and nitrogen fixers (Azospirillum amazonense and Azotobacter sp.) on soil enzyme activities and microbial characteristics of soil under turmeric cultivation. The single, dual and consortium inoculations showed higher enzyme activities over control. Results revealed an increase in phosphatase (18.3–21.3 μmol p-nitrophenol g−1 h−1), dehydrogenase (83.4–100.5 nmol TPF g−1 h−1) and urease (83.2–99.5 μmol NH3-N g−1 h−1) enzyme activities along with an increase of 1.30–1.82 μg g−1 soil microbial biomass carbon content. Besides, mycorrhizal colonization rate showed a similar pattern in dual and consortium inoculation with single inoculation of arbuscular mycorrhizal fungi (95.2–97%) suggesting the plant growth promoting microbes as mycorrhiza helper bacteria for a clear preference as bioinoculants to be used for a sustainable agricultural strategy.