Identification of drought-tolerant plants for roadside greening-An evaluation of chlorophyll fluorescence as an indicator to screen for drought tolerance

摘要

Drought is a major limitation to plant growth and development so the identification of suitable screening techniques and quantifiable traits associated with drought tolerance can potentially help reduce the impact of water deficit on plant replacement needs and allow for remedial action where necessary to be undertaken. Twelve species of flowering plants (Excocecaria cochinensis Lour., Russelia equisetiformis Schlecht. & Cham., Lantana montevedensis (Spreng.) Briq., Phyllanthus cochinchinensis (Lour.) Spreng., Evolvulus pilosus Syne.. Talinum triangulare (Jacq.) Willd., Coreopsis grandiflora Hogg ex Sweet. Chlorophytum cosmosum (Thunb.) Jacques.. Elephantopus scaber L. Periscaria hydropiper (L) Spach., Stenotaphrum secundatum (Walter.) Kuntze. and Tradescantia pendula (Schnizl.) Hunt.) commonly planted along streets and roads for aesthetic purposes were examined here using the chlorophyll fluorescence ratio (F-v/F-m - measure of photochemical efficiency) and digital image analysis of green foliage coverage. Both have been confirmed to be reliable indicators in the identification of drought tolerant and susceptible species. Plants were initially allowed to establish for 60 days under adequate irrigation following containerization (establishment phase). This was followed by another 60 clays of drought (drought phase). For the last 60 days of the experiment, plants were re-watered and allowed to recover (recovery phase). Based on fluctuations in photochemical efficiency over the different phases, five species were identified as susceptible to drought whilst another five were considered to have the ability to resist water stress and two were identified as drought intermediate species - exhibiting reduced sensitivity to drought conditions where a decline in values of GIG, were only observed in the recovery phase. One of the drought intermediate species (T. triangulare) exhibited little to no relationship between chlorophyll fluorescence and soil moisture content. Plants were deemed drought tolerant through stable Fv/Fm values and lower leaf senescence as recorded by a greater extent of green foliage at the end of the drought and recovery phase. The identification of drought tolerant and susceptible species was further confirmed through regression analysis of F-v/F-m and soil moisture content where linear relationships were observed between leaf chlorophyll fluorescence and soil moisture for most of the plants examined in this study. Results of this study strongly suggest that evaluation of whole shrubs using chlorophyll fluorescence is capable of providing a means to identifying the susceptibility of plants to water stress