Impact of Water Quality on the Anatomical and Histochemical …
5
3 Results and Discussion
3.1 Anatomical Studies of Water Hyacinth
3.1.1 Leaf
Leaf possess predominant upper and lower epidermal layers. Epidermis was
composed of single-layered parenchyma cells arranged without any spaces.
Epidermis was surrounded by thin cuticle. Bulliform cells were seen in the upper
epidermis. Ground tissue contains uniform palisade cells. Palisade layer was found
on both the upper and lower side beneath the epidermis. Aerenchyma cells were
found in the mesophyll layer. Vascular bundles were found randomly in the mesophyll of the leaf. Bundles were of two types (smaller and larger). Xylem tissues
consist of tracheids, vessels, fibres and parenchyma cells. Phloem was composed
of sieve tubes and companion cells. Phloem fibres and parenchyma cells were also
present. Each bundle has bundle sheath made up of sclerenchyma cells. Sclereids
were found in cells facing airspaces. Water cavity or protoxylem lacuna was found
in the mesophyll of the leaf. Stomata were found in the upper epidermis, but in
some cases the leaf is amphistomatic. The subsidiary cells were parallel and exhibited paracytic stomata. Subsidiary cells were surrounded by many epidermal cells.
Guard cells contain chloroplast and thus help in photosynthesis. Stomata help in
controlling transpiration, thereby aid in leaf cooling, metabolite fluxes, and longdistance signalling as well as acting as a barrier to harmful pollutants such as ozone
and pathogens (Meidner and Mansfield 1968; Mansfield and Majernik 1970). In the
leaf of Singanallur sample, vascular bundles were surrounded by 7–8 cells. In leaf
samples collected from Sulur, two or more vascular bundles were found attached
together like a single bundle (Table 1).
3.1.2 Petiole
Epidermis of petiole was made of single-layered parenchyma cells (Mahmood et al.
2005). Cuticle was absent. Large air spaces were present in the hypodermis of petiole.
Sclereids were observed arising from the aerenchyma cells projecting into air spaces.
Few raphide crystals were also observed in petiole. Inclusions were found in the hypodermis. Scattered vascular bundles were found smaller and large in number towards
the epidermis. Xylem tissues consist of tracheids, vessels, fibres and parenchyma
cells. Phloem was composed of sieve tubes and companion cells. Phloem fibres and
parenchyma cells were also present. Each bundle has bundle cap made up of sclerenchyma cells. The hexagonal air spaces were surrounded by bands of single-layered
parenchyma cells. Dutta (1986) reported that petiole was a pseudobulb with many
air chambers for facility of floating. Pith was absent. Petiole of this plant collected
from Singanallur, Yakra and Sulur exhibited the presence of numerous sclereids and
those gathered from Ukkadam samples possessed numerous raphides (Table 2).
5
3 Results and Discussion
3.1 Anatomical Studies of Water Hyacinth
3.1.1 Leaf
Leaf possess predominant upper and lower epidermal layers. Epidermis was
composed of single-layered parenchyma cells arranged without any spaces.
Epidermis was surrounded by thin cuticle. Bulliform cells were seen in the upper
epidermis. Ground tissue contains uniform palisade cells. Palisade layer was found
on both the upper and lower side beneath the epidermis. Aerenchyma cells were
found in the mesophyll layer. Vascular bundles were found randomly in the mesophyll of the leaf. Bundles were of two types (smaller and larger). Xylem tissues
consist of tracheids, vessels, fibres and parenchyma cells. Phloem was composed
of sieve tubes and companion cells. Phloem fibres and parenchyma cells were also
present. Each bundle has bundle sheath made up of sclerenchyma cells. Sclereids
were found in cells facing airspaces. Water cavity or protoxylem lacuna was found
in the mesophyll of the leaf. Stomata were found in the upper epidermis, but in
some cases the leaf is amphistomatic. The subsidiary cells were parallel and exhibited paracytic stomata. Subsidiary cells were surrounded by many epidermal cells.
Guard cells contain chloroplast and thus help in photosynthesis. Stomata help in
controlling transpiration, thereby aid in leaf cooling, metabolite fluxes, and longdistance signalling as well as acting as a barrier to harmful pollutants such as ozone
and pathogens (Meidner and Mansfield 1968; Mansfield and Majernik 1970). In the
leaf of Singanallur sample, vascular bundles were surrounded by 7–8 cells. In leaf
samples collected from Sulur, two or more vascular bundles were found attached
together like a single bundle (Table 1).
3.1.2 Petiole
Epidermis of petiole was made of single-layered parenchyma cells (Mahmood et al.
2005). Cuticle was absent. Large air spaces were present in the hypodermis of petiole.
Sclereids were observed arising from the aerenchyma cells projecting into air spaces.
Few raphide crystals were also observed in petiole. Inclusions were found in the hypodermis. Scattered vascular bundles were found smaller and large in number towards
the epidermis. Xylem tissues consist of tracheids, vessels, fibres and parenchyma
cells. Phloem was composed of sieve tubes and companion cells. Phloem fibres and
parenchyma cells were also present. Each bundle has bundle cap made up of sclerenchyma cells. The hexagonal air spaces were surrounded by bands of single-layered
parenchyma cells. Dutta (1986) reported that petiole was a pseudobulb with many
air chambers for facility of floating. Pith was absent. Petiole of this plant collected
from Singanallur, Yakra and Sulur exhibited the presence of numerous sclereids and
those gathered from Ukkadam samples possessed numerous raphides (Table 2).