Extrafloral nectary-bearing plant Mallotus japonicus uses different types of extrafloral nectaries to establish effective defense by ants.

Extrafloral nectary (EFN)-bearing plants attract ants to gain protection against herbivores. Some EFN-bearing plants possess different types of EFNs, which might have different effects on ants on the plants. Mallotus japonicus (Thunb.) Muell. Arg. (Euphorbiaceae) bears two types of EFNs, including a pair of large EFNs at the leaf base and many small EFNs along the leaf edge. This study aimed to determine the different roles of the two types of EFNs in biotic defense by ants. A field experiment was conducted to investigate the effect of leaf damage on EFN production and on the distribution pattern of ants. After leaf damage, the number of leaf edge EFNs increased in the leaves first-produced. The number of ants on the leaves also increased, and the foraging area of ants extended from the leaf base to the leaf tip. An EFN-covering field experiment revealed that leaf edge EFNs had a greater effect than leaf base EFNs on ant dispersal on leaves. The extended foraging area of ants resulted in an increase of encounter or attack rate against an experimentally placed herbivore, Spodoptera litura. These results suggest that M. japonicus plants control the foraging area of ants on their leaves using different types of EFNs in response to leaf damage, thus achieving a very effective biotic defense against herbivores by ants.

Glandular hair constituents of Mallotus philippinensis Muell. fruit act as tyrosinase inhibitors: Insights from enzyme kinetics and simulation study.

The glandular hair extracts from the fruit rind of Mallotus philippinensis Muell. is employed to treat various skin infections, however the anti-tyrosinase activity remains unknown. Hence the present study inspected on the anti-melanogenic activity of M. philippinensis constituents. Lineweaver Burk plot revealed mixed inhibition for Rottlerin; non-competitive type of inhibition for mallotophilippen A and B respectively. Thermodynamic studies resulted in static quenching forming ground state complex with higher binding constant temperature dependently. Fluorescence and circular dichroism study implicated conformational change in secondary and tertiary structure of tyrosinase. Molecular docking suggests rottlerin has high binding affinity to the active site pocket of tyrosinase. Simulation study further proved that the compactness of inhibitor with tyrosinase by hydrogen bonding influenced the stability of the enzyme. Depigmentation efficacy is further proved in Aspergillus niger spores. Thus our findings delineate that rottlerin could be utilized as a depigmentation agent in food pharmaceutical and agricultural industries.

The limited importance of size-asymmetric light competition and growth of pioneer species in early secondary forest succession in Vietnam.

It is generally believed that asymmetric competition for light plays a predominant role in determining the course of succession by increasing size inequalities between plants. Size-related growth is the product of size-related light capture and light-use efficiency (LUE). We have used a canopy model to calculate light capture and photosynthetic rates of pioneer species in sequential vegetation stages of a young secondary forest stand. Growth of the same saplings was followed in time as succession proceeded. Photosynthetic rate per unit plant mass (P(mass): mol C g(-1) day(-1)), a proxy for plant growth, was calculated as the product of light capture efficiency [Phi(mass): mol photosynthetic photon flux density (PPFD) g(-1) day(-1)] and LUE (mol C mol PPFD(-1)). Species showed different morphologies and photosynthetic characteristics, but their light-capturing and light-use efficiencies, and thus P (mass), did not differ much. This was also observed in the field: plant growth was not size-asymmetric. The size hierarchy that was present from the very early beginning of succession remained for at least the first 5 years. We conclude, therefore, that in slow-growing regenerating vegetation stands, the importance of asymmetric competition for light and growth can be much less than is often assumed.