Morphological and physiological responses of Triglochin buchenaui Köcke, Mering & Kadereit to various combinations of water and salinity: implications for resilience to climate change

Abstract

Impacts of abiotic factors on low lying salt marsh species have been closely evaluated as unique stressors, but few studies have determined the physiological and morphological responses to predicted climate change conditions. This study investigated the effects of water state (tidal, flooded and drought) and salinity on Triglochin buchenaui Kocke, Mering and Kadereit, newly separated from the Triglochin bulbosa L. complex. Growth, proline concentration, relative water content, electrolyte leakage, chlorophyll concentration and morphological analyses were done following 3 months of treatments. Results showed significant variation in height (7.57 ± 0.5–29 ± 1.55 cm, p < 0.005, df = 55), leaf area increments and relative growth rates which decreased with increasing salinity under all water states. There was almost a cessation of growth under submergence which reduces the plant’s regeneration potential under these conditions. Proline accumulation (1.84 ± 0.23–3.36 ± 0.38 mg g−1 DW), response of photosynthetic pigments and electrolyte leakage (8.17 ± 0.80–38.36 ± 7.42 % μS g−1 FW) were fundamental to osmotic and membrane response regulation. Plants survived in all water states at salinity up to 45 ppt, but the optimum range was 0–18 ppt, and best water state was the tidal condition. Viable rhizomes were produced under drought conditions but in the absence of seed banks, regeneration of the species following prolonged submergence may not be possible due to absence of both rhizomes and seeds. In their natural habitat, highly succulent T. buchenaui plants (29 ± 1.55 cm tall and above) are indicative of freshwater conditions.