Nepenthes pitcher plants are typically carnivorous, producing pitchers with varying combinations of epicuticular wax crystals, viscoelastic fluids and slippery peristomes to trap arthropod prey, especially ants. However, ant densities are low in tropical montane habitats, thereby limiting the potential benefits of the carnivorous syndrome. Nepenthes lowii, a montane species from Borneo, produces two types of pitchers that differ greatly in form and function. Pitchers produced by immature plants conform to the 'typical' Nepenthes pattern, catching arthropod prey. However, pitchers produced by mature N. lowii plants lack the features associated with carnivory and are instead visited by tree shrews, which defaecate into them after feeding on exudates that accumulate on the pitcher lid. We tested the hypothesis that tree shrew faeces represent a significant nitrogen (N) source for N. lowii, finding that it accounts for between 57 and 100 per cent of foliar N in mature N. lowii plants. Thus, N. lowii employs a diversified N sequestration strategy, gaining access to a N source that is not available to sympatric congeners. The interaction between N. lowii and tree shrews appears to be a mutualism based on the exchange of food sources that are scarce in their montane habitat.
The extraordinary level of accumulation of nickel (Ni) in hyperaccumulator plants is a consequence of specific metal sequestering and transport mechanisms, and knowledge of these processes is critical for advancing an understanding of transition element metabolic regulation in these plants. The Ni biopathways were elucidated in three plant species, Phyllanthus balgooyi, Phyllanthus securinegioides (Phyllanthaceae) and Rinorea bengalensis (Violaceae), that occur in Sabah (Malaysia) on the Island of Borneo. This study showed that Ni is mainly concentrated in the phloem in roots and stems (up to 16.9% Ni in phloem sap in Phyllanthus balgooyi) in all three species. However, the species differ in their leaves - in P. balgooyi the highest Ni concentration is in the phloem, but in P. securinegioides and R. bengalensis in the epidermis and in the spongy mesophyll (R. bengalensis). The chemical speciation of Ni2+ does not substantially differ between the species nor between the plant tissues and transport fluids, and is unambiguously associated with citrate. This study combines ion microbeam (PIXE and RBS) and metabolomics techniques (GC-MS, LC-MS) with synchrotron methods (XAS) to overcome the drawbacks of the individual techniques to quantitatively determine Ni distribution and Ni2+ chemical speciation in hyperaccumulator plants.
Pineapple (Ananas comosus var. comosus) is known as the king of fruits for its crown and is the third most important tropical fruit after banana and citrus. The plant, which is indigenous to South America, is the most important species in the Bromeliaceae family and is largely traded for fresh fruit consumption. Here, we report the complete chloroplast sequence of the MD-2 pineapple that was sequenced using the PacBio sequencing technology.
Rafflesiaceae, which produce the world's largest flowers, have captivated the attention of biologists for nearly two centuries. Despite their fame, however, the developmental nature of the floral organs in these giants has remained a mystery. Most members of the family have a large floral chamber defined by a diaphragm. The diaphragm encloses the reproductive organs where pollination by carrion flies occurs. In lieu of a functional genetic system to investigate floral development in these highly specialized holoparasites, we used comparative studies of structure, development, and gene-expression patterns to investigate the homology of their floral organs. Our results surprisingly demonstrate that the otherwise similar floral chambers in two Rafflesiaceae subclades, Rafflesia and Sapria, are constructed very differently. In Rafflesia, the diaphragm is derived from the petal whorl. In contrast, in Sapria it is derived from elaboration of a unique ring structure located between the perianth and the stamen whorl, which, although developed to varying degrees among the genera, appears to be a synapomorphy of the Rafflesiaceae. Thus, the characteristic features that define the floral chamber in these closely related genera are not homologous. These differences refute the prevailing hypothesis that similarities between Sapria and Rafflesia are ancestral in the family. Instead, our data indicate that Rafflesia-like and Sapria-like floral chambers represent two distinct derivations of this morphology. The developmental repatterning we identified in Rafflesia, in particular, may have provided architectural reinforcement, which permitted the explosive growth in floral diameter that has arisen secondarily within this subclade.