Distribution of tension wood like gelatinous fibres in the roots of Acacia nilotica (Lam.) Willd.

KEY MESSAGE: The present study unravels the anatomical characteristics and distribution patterns of cell wall polymers in the G-fibres found in the roots of A. nilotica using different microscopy techniques (light, electron and immunofluorescence microscopy). The present study was aimed to investigate the anatomy of reaction xylem in the positively gravitropic roots of Acacia nilotica growing in compact and waterlogged soils. The roots collected from the two different sites showed occurrence of gelatinous fibres throughout xylem radii from a distance of 4 cm from the soil surface. The thickness of gelatinous layer (G-layer) increased in the root collected from the deeper soil. Further, the ultrastructural studies revealed a complete replacement of S2 and S3 layers in G-fibres nearer to root tip region as compared to the root portion close to upper part of the soil surface. In addition, these fibres demonstrated intense lignification in compound middle lamellae region of G-fibre walls. Moreover, the vessel density and their width increased considerably near the root tip region. The immunofluorescence analysis suggested that the ß-1,4-galactans were prevalent in G-layer, whereas the xylan was restricted to only regions of lignified secondary wall. The similarities in distribution pattern and anatomical features of G-fibres in waterlogged and non-waterlogged roots suggest the occurrence of G-fibres as inherent characteristics in the roots of Acacia nilotica.

Chemical Composition in Juvenile and Mature Wood of Branch and Main Trunk of Leucaena leucocephala (Lam.) de Wit.

Secondary growth is the most dynamic developmental aspect during the terrestrialization of plants. The development of secondary xylem tissue composed of thick-walled cells with characteristic changes in its structure and chemistry facilitates the growth and development of woody plants. In the present study, the chemical composition of the secondary xylem of juvenile and mature wood from the branch and main trunk of Leucaena leucocephala, has been investigated and the differences established. The biochemical analysis of different cell wall components in the mature wood of the main trunk revealed high holocellulose and α-cellulose and less lignin content in the juvenile wood while its syringyl/guaiacyl (S/G) ratio was less than for the mature wood. As compared to the branch xylem, concentration of cell wall polysaccharides and lignin content was higher in both juvenile and mature wood collected from the main trunk. Thioacidolysis and GC-MS analysis of wood lignin from juvenile and mature wood showed that an increased concentration in lignin content in mature wood is associated with a corresponding increase in S/G ratio. The structural information of the acetylated lignin was investigated by 1H NMR spectroscopy. Our results indicate that the mature wood from the main trunk is superior in pulp yielding and lignin degradability as compared to the juvenile wood of the branch and trunk.

Immunolocalization of ß-(1-4)-D-galactan, xyloglucans and xylans in the reaction xylem fibres of Leucaena leucocephala (Lam.) de Wit.

Cell wall architecture of tension wood fibres represents a suitable biological system to study the mechanism of growth and maintenance of posture of trees growing under various physical and physiological growth constraints. In the present study, we investigated the spatial distributions of ß-(1-4)-D-galactan, xyloglucan and xylans (both less and highly substituted) in the opposite and tension wood fibres of bent Leucaena leucocephala by immunolabelling with monoclonal antibodies LM5, CCRCM1, LM10 and LM11 specific to these carbohydrate epitopes. The presence of non-lignified, tertiary wall layer is the typical tension wood characteristic associated with the reaction xylem fibres in Leucaena. LM5 labelling of opposite fibres showed weak labelling in the cell walls indicating less concentration of ß-(1-4)-D-galactans while tension wood showed strong labelling in the tertiary wall layer suggesting the gelatinous layer (G-layer) has a strong cross linking with ß-(1-4)-D-galactans. Xyloglucan distribution was more in the compound middle lamellae and the primary wall-S1 layer boundary of tension wood fibres as compared to that of opposite wood. A weak labelling was also evident near the boundary between the G-layer and the secondary wall of tension wood fibres. The secondary wall of opposite and tension wood fibres showed a strong distribution of both ls ACG Xs (LM10) and hs ACG Xs (LM11) while a weak labelling was noticed in the compound middle lamella. Tension wood fibres also showed strong xylan labelling mainly confined to the lignified secondary walls while the G-layer showed weak xylan labelling. In conclusion, our results suggest that ß-(1-4)-D-galactans and xyloglucans could be implicated in the tensile stress generation within the G-layer of tension wood fibres of Leucaena leucocephala.

Isolation, optimization, and partial purification of amylase from Chrysosporium asperatum by submerged fermentation.

A potent fungus for amylase production, Chrysosporium asperatum, was isolated from among 30 different cultures obtained from wood samples collected in the Junagadh forest, India. All of the isolated cultures were screened for their ability to produce amylase by submerged fermentation. Among the selected cultures, C. asperatum (Class Euascomycetes; Onygenales; Onygenaceae) gave maximum amylase production. In all of the different media tested, potato starch was found to be a good substrate for production of amylase enzyme at 30 degrees C and pH 5.0. Production of enzyme reached the maximum when a combination of starch and 2% xylose, and organic nitrogen (1% yeast extract) and ammonium sulfate were used as carbon and nitrogen sources, respectively. There was no significant effect of metal ions on enzyme activity. The enzyme was relatively stable at 50 degrees C for 20 min, and no inhibitory effect of Ca+2 ions on amylase production was observed.

Morpho-anatomy of Solanum pseudocapsicum

Morpho-anatomical features in leaves, stems and unripe fruits of Solanum pseudocapsicum L., Solanaceae, were investigated by histological methods. Anatomically the plant may be characterised by the presence of uniseriate trichomes, anomocytic stomata, calcium oxalate needles in leaves while presence of oval to circular compound starch grains, angular vessels, vertically upright, uni-biseriate rays and intraxylary phloem with differentiation of internal cambium abutting marginal pith cells and protoxylem in transverse view. Development of distinct internal cambium may be considered as a characteristic feature for S. pseudocapsicum. Intraxylary secondary phloem was composed of sieve tube elements, companion cells and axial parenchyma cells.