Physiological response of selected avocados (Persea americana) subjected to NaCl and NaHCO3 stress

Alkali stress on crops has gained importance around the world in recent years. Avocado (Persea americana Mill.) is considered a salt-sensitive species, but the effect of alkaline water on avocados has not been sufficiently studied. Biomass, gas exchange, chlorophyll-a fluorescence, photosynthetic pigments and tocopherols were evaluated in response to alkali salt (NaHCO3) and neutral salt (NaCl) stresses on avocado. Three irrigation treatments were applied: Control (no added salt), 1 g l(-1) NaCl and 1.5 g l(-1) NaHCO3 for a period of 5 months. Six clonally propagated avocado rootstocks were employed, four local selections of West Indian and two Mexican race rootstocks. Biomass reduction was observed in both salt treatments, especially in the roots under the alkali stress. A reversible photoinhibition, a lower photochemical efficiency of PSII and a greater oxidative stress were detected in the alkali stressed avocados. Although biomass was reduced under salt and alkali stress, alkali stress harmed the photosynthetic apparatus to a greater extent than salt stress. Further research is necessary, the problem of alkali stress is increasing, especially in places with alkali waters where salt sensitive species such as avocado is cultivated.