Ammonium stress and supplemental calcium influence growth of in vitro cultured blueberry plantlets

摘要

Background of the study - Salt damage has recently become a serious problem worldwide. Though ammonium-N is widely used as the main N source for growth of blueberry, few studies on ammonium damage to blueberry were reported. Objectives - The current research aimed to explore the effects of ammonium stress and supplemental calcium on blueberry growth using an in vitro model. Methods - In vitro cultured blueberry plantlets subjected to 1/4 MS itself containing 0.005M NH4+, 1/4 MS containing 0.01M NH4+, 1/4 MS containing 0.02M NH4+, 1/4 MS containing 0.02M NH4+ plus 0.01M Ca2+. Plant biomass, nutrient compositions and anti-oxidants in plantlets were analyzed. Results - Ammonium stress induced by 0.02M NH4+ significantly inhibited growth of in vitro cultured blueberry. Plants under ammonium stress showed the highest contents of N and Fe, and lowest contents of K, Ca, Mg and Mn. Ammonium stress also significantly inhibited contents of proline (Pro), Methane Dicarboxylic Aldehyde (MDA), soluble protein (SP) and the activity of superoxide dismutase (SOD), and promoted the activities of catalase (CAT), peroxidase (POD) and glutamine synthetase (GS). 0.01M supplemental Ca2+ proved to enhance the growth of blueberry plantlets exposed to ammonium stress with the obviously increased contents of K, Ca, Mg and Mn, Pro, MDA, SP and the increased activity of SOD. Close correlations were observed among plant biomass, nutrient compositions and anti-oxidants in blueberry plantlets. Conclusions - Ammonium stress affects growth of blueberry plantlets by regulating the allocation of nutrient composition and the anti-oxidant activity, which closely correlate with calcium signaling pathways. Supplemental Ca2+ could prevent ammonium damage. In vitro culture used as a model provides an effective and promising approach for study of plant stress, and a powerful technical support for field management of Vaccinium plants.