Leaf secretion composition of the mangrove species Avicennia germinans (L.) in relation to salinity: a case study by using total-reflection X-ray fluorescence analysis

• Published in: Plant science (Limerick) Vol. 159; no. 1; pp. 1 - 5
• Main Authors: Sobrado, M.A., Greaves, E.D.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 16-10-2000; Elsevier Science
• Subjects: Absorption. Translocation of ions and substances. Permeability; Agronomy. Soil science and plant productions; Avicennia germinans; Biological and medical sciences; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Gland secretion; Mangroves; Nutrition. Photosynthesis. Respiration. Metabolism; Plant physiology and development; Salinity; Total-reflection X-ray fluorescence; Trace element analysis; Water and solutes. Absorption, translocation and permeability; Mangroves; Avicennia germinans; Trace element analysis; Total-reflection X-ray fluorescence; Salinity; Gland secretion; Halophyte; Ionic regulation; Secretion; X ray fluorescence; Plant leaf; Inorganic element; Case study; Verbenaceae; Mangrove; Dicotyledones; Angiospermae; Hardwood forest tree; Spermatophyta; Chemical composition; Measurement method; Total reflection; Sodium Chlorides
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/S0168-9452(00)00292-2

The aim here was to use total-reflection X-ray fluorescence (TXRF) to determine the elemental composition (besides Na), and the relative contribution of each element in leaf secretion of the mangrove species
Avicennia germinans, grown under contrasting salinities (0–865 mol m
−3 NaCl). Na was determined by conventional atomic absorption spectrometry (AAS). Total secretion was 2.00±0.28 mmol m
−2 per day in control plants (at 0 NaCl) and increased progressively up to 46.87±7.14 mmol m
−2 per day at 865 mol m
−3 NaCl. Na and Cl accounted for 85.91±1.81% of the total secretion in control plants and about 96.32±0.30% in salt-treated plants. The excretion of Na exceeded that of Cl when salinity increased and this led to a progressive increase in Na/Cl ratios from 0.46±0.02 in control plants up to 2.75±0.42 (at 865 mol m
−3 NaCl). Other elements were also secreted in sizeable amounts such as K, S, Ca, Br and Zn. However, the relative importance of these elements, in terms of total secretion, was considerable in control plants (15% of the total secretion) and declined significantly under salinity treatments (<5% of the total secretion). In conclusion, TXRF has been shown to be a powerful tool allowing quantitative determination of Cl (1.2–13 mmol m
−2 per day), secreted in relatively large quantities, as well as other elements secreted in intermediate (S, Ca and K; 0.07–1.00 mmol m
−2 per day) and in trace quantities (Br and Zn; 0.6–4 μmol m
−2 per day).