Screening Growth and Root Formation in Cadmium-Treated Turfgrass Using a Whole-Plant Microculture System

Abstract

Pollution of water and soil by heavy-metal byproducts of mining and industrial operations is an environmental problem in many parts of Taiwan. Bermudagrass (Cynodon dactylon) and seashore paspalum (Paspalum vaginatum Swartz) are two of the most saline-tolerant warm-season turfgrasses. A whole-plant microculture (WPMC) system has been developed that permits intact-root growth observation through a gelrite-solidified culture medium. To screen efficiently for potential whole-plant-level salt tolerance in these turfgrasses, root morphology was studied using scanning electron microscopy. Nodal explants at the same developmental stage as the plants were sterilized, and each explant was placed in a Pyrex test tube containing 25 mL of 1/2 Murashige and Skoog (MS) media with 30 g L− 1 sucrose, 1 mg L− 1 IBA, 0.1 mg 2ip, 2.5 g L− 1gelrite, and either 0, 1, or 100 ppm of CdCl2 stress media for five months. The experimental results demonstrated significant differences among stress media in terms of root number, root length, shoot length, nodal number, and ratio of root length to shoot length of plants. Moreover, scanning electron microscopy (SEM) examination of regenerated WPMC roots under cadmium (Cd)-free, 1, and 100 ppm of CdCl2 stress media revealed obvious morphological and adaptational differences. In this investigation, microculture at the whole-plant level in vitro enables intact root growth observations through the culture medium and vessel, and offers a potential pre-screening method for putative heavy-metal-tolerant turfgrasses before commercialization and use in phytoremediation to clean up contaminated soils.