GRASSES OF THE NEELUM VALLEY AZAD JAMMU AND KASHMIR: SYSTEMATICS, ANATOMY AND PHYSIOLOGY

Abstract

Grasses belong to one of the most fascinating families of flowering plants, family Poaceae with a wide range of diversity. Poaceae is a species-rich family that includes many economic plants, globally with about 10,000 species and 700 genera. The members of this group are present in all the conceivable habitats suitable for the growth of the plant communities. Recent phylogenetic studies confirmed that multiple factors are involved indirectly that determine the grass diversity at large scales. A total of 52 species of grasses belonging to 10 tribes and 28 genera were recorded from 15 sampling sites in Neelum Valley, Azad Jammu and Kashmir. Physiochemical characteristics of the soil showed that most of the soil component varied significantly over different sites. The soil moisture content seemed to be closely related to the physical properties of the soil as well as to vegetation type. Morphological markers are helpful in the identification, differentiation and classification of the grasses at species, genus and tribe level. Significant variations in different morphological characters are observed in different genera of the same tribe and among the species of the same genus. Poaceae shows great variety in anatomical characteristics especially leaf anatomical parameters more than any other plant family and provides extensive data for systematic utilization. At root, stem and leaf level, anatomical characteristics of grasses showed significant variation among the tribes and within the species. Grasses showed angular prickles at the margin of the leaf in costal and intercostal zone, long cells with slightly sinuous walls, sharply pointed micro hairs and saddle, X or rounded shape silica bodies. Certain shapes of silica bodies were characteristic of grass subfamilies, e.g. dumbbell-shaped in panicoid grasses, saddle-shaped in most pooid grasses. Adaxial and abaxial surfaces of the leaf showed high number of ribs and ridges, with increase number of hairiness in most of the grasses. Tribe Paniceae, showed highly pointed angular bicelled prickles and micro hairs at the leaf margins that is characteristic feature of this tribe. Anatomical alterations such as enlarged succulence, sclerification, highly developed bulliform cells, endodermis in stem or roots and metaxylem area the indumentum of leaves and length and frequency of epidermal basis play an important role in the tolerance of various altitudinal stresses. The diversity in anatomical markers could be used to clarify the status of problematic taxa in different tribes. Presence of sclerenchyma strands on the abaxial side only makes the genus Cenchrus distinct it from the remaining species within the tribe. Saddle shaped silica bodies, microhairs and bulliform cells deeply penetrating the mesophyll were found the prominent characters of these tribes. The cladistics analysis of Andropogoneae showed Schizachyrium as the first branch within Andropogoneae, clustered with [Apluda+ Arthraxon]; then was sister to [Bothriochloa+ Heteropogon], collectively sister to the remaining crown clade ([Saccharum+Sorghum] + Capillipedium). Heteropogon spp. showed a close relationship with two xiv Bothriochloa spp. whereas, Capillepidium was found much closer to the species of Sorghum and Saccharum. Phylogenetic analysis of molecular data showed Apluda (Apluda mutica) at the first branch within tribe Andropogoneae, sister to the remaining genera with robust support (PP = 1.00, BS = 100; or 1.00/100). Arthraxon (Arthraxon hispidus) was sister to the left 6 genera (Saccharum, Sorghum, Capillipedium Schizachyrium, Heteropogon, and Bothriochloa) with high PP value (0.96), but no bootstrap values. The Saccharum+Sorghum clade was sister to the crown clade (1.00/64) without PP and BS. Within the crown clade, Schizachyrium clustered with the left genera ([Heteropogon + Capillipedium] + Bothriochloa) as sister (0.97/53); Heteropogon was sister to the genus Bothriochloa with strong support values (1.00/91). Almost all morpho-anatomical and physiological characteristics are species specific and also specific in their degree of tolerance to either cold stress or drought. However, some specific modifications like amount of sclerification, size and shape of bulliform cells, presence of storage parenchyma, nature of pubescence and stomatal size and area can be related to environmental conditions. It is, therefore, concluded that certain anatomical characteristics like presence of silica bodies, surface appendages, bulliform cells and pattern of sclerification can safely be used as important tools for the identification at species or lower rank and formal taxonomic and nomenclatural changes should surely only be encouraged, particularly at the species level, when the lineages within a phylogeny correlate with morphological characters.