Impact of defoliation intensities on plant biomass, nutrient uptake and arbuscular mycorrhizal symbiosis in Lotus tenuis growing in a saline-sodic soil

I. GARCÍA ; R. MENDOZA

PLANT BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Berlin; Año: 2012 vol. 14 p. 964 - 971

1435-8603

The impact of different defoliation intensities on the ability of Lotus tenuis plants to regrowth, mobilize nutrients, and to associate with native AM fungi and Rhizobium in a saline-sodic soil was investigated. After 70 days, plants were subjected to 0, 25, 50, 75 and 100% defoliation and the shoot regrowth was assessed at the end of subsequent 35 days. Compared to non-defoliated plants, low or moderate defoliations up to 75% did not affect shoot regrowth. However, 100% treatment affected shoot regrowth and the clipped plants were not able to compensate the growth attained by non-defoliated plants. Root growth was more affected by defoliation than shoot growth. P and N concentrations in shoots and roots increased with increasing defoliation meanwhile Na+ concentration in shoots of non-defoliated and moderately defoliated plants was similar. Non-defoliated and moderately defoliated plants prevented increases of Na+ concentration in shoots by both reducing Na+ uptake and Na+ transport to shoots by accumulating Na+ in roots. At high defoliation, the salinity tolerance mechanism is altered and Na+ concentration in shoots was higher than in roots. Reduction in the photosynthetic capacity induced by defoliation neither changed the root length colonized by AM fungi nor the arbuscular colonization but it decreased the vesicular colonization. Spore density did not change, but hyphal density and Rhizobium nodules increased with defoliations. The strategy of the AM symbiont consists in investing the most of the C resources to preferentially keep the arbuscular colonization as well as the inoculum density in soil.