Changes in root morphology accompanying mycorrhizal alleviation of phosphorus deficiency in micropropagated Annona cherimola Mill. plants

The effect of the mycorrhizal inoculation on survival rate, growth, nutrient uptake and root morphology during the acclimatization period and plant establishment of micropropagated juvenile or adult cherimoya plants (Annona cherimola Mill.) was determined. Although mycorrhizal colonization did not improve the survival rate of plants, which was already high in non-inoculated plants, it had a positive effect on plant development (shoot length, leaf number, leaf area and fresh and dry weights). Mycorrhizal juvenile plants tripled the macronutrients and increased by four the micronutrient uptake, and mycorrhizal adult plants increased by two phosphorus and all micronutrients, with copper uptake increased five times. Moreover, mycorrhizal colonization changed the root morphology of adult plants increasing three-fold the total number of roots, doubling the number of first-order laterals and increasing second-order laterals by four. Total root length was also increased three-fold, adventitious root length was almost doubled, first-order laterals tripled and second-order roots length increased four-fold. The effect of mycorrhizal colonization seems to be stronger or different in juvenile than in adult plants, suggesting that ontogenic stage is an important factor determining mycorrhizal effect and the plant performance during the acclimatization period. (c) 2005 Elsevier B.V. All rights reserved.