Effect of Air-Borne Salinity on the Growth and Appearance of the Tropical Perennial Strandline Plant, Commelina erecta subsp. maritima (C.V. Morton) C.V. Morton

Otitoloju Kekere

doi:10.5539/sar.v3n2p77

Abstract

Selection of salt spray tolerant plants with good physical appearance is of concern to ornamental growers in coastal communities. Commelina erecta subsp. maritima (C.V. Morton) C.V. Morton is a seashore plant that is widely distributed along the coast of West Africa. Therefore, the effect of salt spray was examined on the plant in a greenhouse experiment to determine its responses to various levels of air-borne salinity and to have an insight in the ecophysiological adaptations underlying these responses. It was also aimed to determine if varying levels of salt spray differentially damaged the plant. Filtered seawater was used to spray potted plants at: two sprays per week (2SS), four sprays per week (4SS) or six sprays per week (6SS) while in the control treatment (CSS), plants were sprayed with deionized water. Plants sprayed with seawater did not differ significantly (p &gt; 0.05) in percentage necrotic leaf area compared to the control. All the plants survived but growth was inhibited by salt spray. Salt spray caused a significant (p &lt; 0.05) reduction in leaf size and total chlorophyll content. Salt was accumulated in the shoot of salt-sprayed plants which led to ion toxicity. Salt sprays led to reduction in amount of essential nutrients in plant parts. C. erecta subsp. maritima adjusted osmotically to salt stress and increased stem succulence for ion dilution. The growth of the plant was negatively affected by salt sprays but it showed no significant necrotic damage, hence it is suitable for use as a landscaping plant in coastal beaches.

Highlights

Plants that tolerate coastal conditions have become increasingly important in coastal communities where drift materials are deposited by spring tides or storms as strandline
Leaf area reduction is in conformity with the results reported for Pinus rigida (Griffiths & Orians, 2004) and Diodia maritima (Kekere & Bamidele, 2012) following exposure to salt sprays
It was reported that necrotic levels were not affected by salt spray in Myrica pensylvanica seedlings in a greenhouse experiment (Griffiths & Orians, 2003). They attributed low necrosis probably because the leaf surface has thick cuticle to limit salt entry or since the plant was grown in the protective environment of the greenhouse, the leaves had few stomata to reduce entry points to salt spray

Summary

Introduction

Plants that tolerate coastal conditions have become increasingly important in coastal communities where drift materials are deposited by spring tides or storms as strandline. The salts may enter the aerial organs of the plants, especially where small surface injuries are present (Boyce, 1954). In this way, it can disrupt the water balance of plants (Munns, 1993), and cause necrosis or loss of leaves and lead to growth reduction (Sykes & Wilson, 1988; Tominaga & Ueki, 1991). Kekere and Bamidele (2012) stated that Diodia maritima seedlings sprayed with seawater had reduced number of leaves and lateral branches, reduction in root growth, number of branches, leaf size and biomass.

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