Zein-based Bioplastic Containers Alter Root-zone Chemistry and Growth of Geranium

Abstract

Bioplastic containers made from zein, a protein from corn ( Zea mays L.), have been developed but not evaluated as alternatives to conventional, petroleum-based plastics. We tested the hypothesis that biodegradation of zein containers provides nitrogen (N) that promotes growth of plants and examined whether plants grown in zein containers could be transplanted successfully without removing the container, thus eliminating the need to dispose of containers. Zein containers provided root zones of geranium ( Pelargonium × hortorum L.H. Bailey) with up to 298 and 277 mg·kg −1 of NH 4 + -N and NO 3 − -N, respectively, and unlike geraniums in conventional plastic containers, leaves of plants in zein containers remained dark green when produced without fertilization. Electrical conductivity and pH of the substrate in zein containers increased above ranges recommended for many horticultural crops, and NO 2 − , which can be toxic to plants, was present in the substrate. These chemical changes may have been responsible for reduced canopy height and width, surface area of selected leaves, length of root systems, and dry weight of shoots of geraniums in zein containers compared with geraniums in conventional plastic containers. In a second experiment, when geraniums were transplanted without removing zein containers, growth of roots and shoots was reduced until after six weeks, when biodegradation of containers was nearly complete, and extension of roots past the zone of the degraded container was documented approximately 12 weeks after transplanting. Geraniums can be produced and transplanted in containers made from zein, but additional research must solve problems that result from altered root-zone chemistry during production and from chemical and physical impediments that delay transplant success.