Radish (Raphanus sativus L.) responds to exogenous ascorbic acid and irrigation levels

Abstract

Plant growth and development depend on water availability and a scarcity or excess can reduce the production of root crops such as radishes. Thus, adequate irrigation levels for radish plants are essential avoid water stress, and to develop strategies to overcome negative stress effects to improve tuber production. Here, we aimed to determine the effects of exogenous ascorbic acid (AA) and irrigation levels on radish growth, biomass allocation and gas exchange. Radish plants were irrigated with a water holding capacity (WHC) of 100% (W100), 70% (W70) and 50% (W50) and foliar sprayed with 0 and 2 mM AA. Growth parameters (root diameter, length and volume; and leaf number and area), biomass accumulation (shoot and root fresh weight; shoot, root and total dry weight), biomass allocation (shoot/root ratio and organ mass fractions) and gas exchange (carbon assimilation rate, stomatal conductance, transpiration, intercellular CO2 concentration and instantaneous carboxylation efficiency) were evaluated. The growth of radish plants was impaired when irrigated with W100, probably due to waterlogging the soil, which reduced shoot and root growth and the carbon assimilation rate (A) compared with W50 and W70. Ascorbic acid affected biomass allocation and instantaneous carboxylation efficiency (A/Ci), but not growth and biomass accumulation. W70 was the optimal condition for radish growth and biomass accumulation, regardless of exogenous AA.