LONG-TERM EFFECT OF SOME HEAVY METAL COMBINATIONS ON GROWTH AND CHEMICAL COMPOSITION OF SOME ORNAMENTAL SHRUBS COMMON IN EGYPT No2. – COMMON OLEANDER (NERIUM OLEANDER L.)

Abstract

An experiment was carried out at Orman Botanical Garden, Giza, Egypt during 2019/20 and 2020/21 seasons to reveal the response of Nerium oleander L. transplants to Pb, Cd, and Ni in combinations at various concentrations after short and long growth periods. Pollution treatments and growth periods were combined factorially to study the effect of interactions. The results showed that survival % was 100% by the various applied treatments. Plant height, stem diameter, and leaf area traits were improved by heavy metal combinations, whereas No. branches and leaves/plant, root length and top growth, and roots fresh and dry weights were negatively affected. Elongating growth period up to 18 months significantly increased means of the different vegetative and root growth traits compared to 6-months period. So, combining between planting in either control or first treatment combination mixture and the longer growth period significantly improved most of the growth parameters. The percent of pollution resistance index took a similar trend, and it was higher than 88% in the two seasons by fourth treatment combination indicating a high tolerance to HMs toxicity. Thus, N. oleander plants can be successfully used for landscaping HMs-polluted sites due to their high survival and tolerance potential.