Morpho-physiology and Anatomy of the Six Grass Species Growing on Lateritic Soil: Diagnosis of Characters for Phytostabilization of Soils Depleted by Mining

Abstract

Due to extensive mining activities, strip vegetation and soil contamination with heavy metals have become common. One of the approaches to ecological restoration is phytostabilization, which uses plants to stabilize and reduce the mobility of heavy metals in the soil. In this study, six species of grasses – namely, Alloteropsis semialata (R.Br.) Hitchc., Cymbopogon citratus (DC.) Stapf, Dinochloa acutiflora (Munro) Soenarko, Imperata cylindrica (L.) Raeusch., Machaerina disticha (C.B. Clarke) T. Koyama, and Panicum repens L. – were collected from a degraded area with lateritic soil in Brgy. Taltal, Masinloc, Zambales, Philippines. The root growth, the direction of roots formed, and mean daily transpiration rate were observed to find a combination of grass species for phytostabilization. Leaf and root anatomical sections were observed using the freehand technique to know the characteristics that enable them to thrive in lateritic soil. D. acutiflora was the only species that exhibited horizontal and spreading roots and the fastest root growth among the six species, whereas A. semialata and P. repens were the deepest penetrating roots among the vertical forming roots. Transpiration rate was the highest at 12:00 PM and is significantly differentiated from 09:00 AM and 04:00 PM – as exhibited by the two exotic species, I. cylindrica and P. repens. Leaf anatomical features in the transverse section – such as thickened epidermal cell walls (anticline), presence of sclerenchyma caps, extended vascular bundles, and bulliform cells – were observed in the leaves of the six species. Root anatomical features observed were thickened epidermal cell walls (anticline), thick endodermis, and a large cortex filled with intercellular spaces (P. repens, D. acutiflora, and M. disticha), as well as black spots in the cortex and pericycle (A. semialata). Knowing these traits, A. semialata, D. acutiflora, and P. repens were found suitable for phytostabilization.