| Blueberries have become one kind of popular fruits in recent years,and research on blueberries is increasing.Blueberries prefer to grow in acid soils,with rhizosphere soil p H values being generally between 4.5 and 5.0.A large amount of manganese,aluminum and other metal ions will precipitate and release from acidic soil,leading to plant growth stressed by manganese and aluminum.In southern Anhui Province,the warm and rainy climate and the acidic red soil are suitable for cultivating blueberry.The growth matrix mainly uses sulfur powder to regulate its soil to be acidic,thus there is a potential risk of the stress by manganese,aluminum,copper,zinc and other metal ion in the soil.However,there are few studies on the toxicity of manganese,aluminum,copper and zinc to blueberry.As a large-scale blueberry planting base in southern Anhui,"Huiwang" Blueberry Company is located in Nanling County,Wuhu City,and plant mainly four cultivated varieties of O'Neill,Baldwin,Ladder bars and Mist.In this study,the blueberry varieties and rhizosphere soil samples were collected,and the manganese pollution and bioaccumulation in each sample were analyzed.Subsequently,the fine blueberry varieties with strong tolerance to manganese were screened.The physiological response,enrichment characteristics and tolerance mechanism of fine blueberries varieties stressed by Mn2+ were studied by indoor hydroponics experiments.The results would provide scientific basis for the evaluation of manganese toxicity and introduction of blueberry in southern Anhui.The main findings are as follows:?1?The soil p H value in "Huiwang" blueberry planting base was about 5.0.No obvious stress by aluminum,copper,zinc,and copper was found.Additionally,zinc and copper content in the soils may be insufficient.However,significant manganese stress in the soils,especially those in low altitude was ascertained.The blueberry is planted in terraces,which cause manganese ions to migrate from high elevation?S1?to low elevation?S8?due to rain erosion and surface runoff.?2?The four varieties of blueberries showed different levels of manganese enrichment,with the enrichment capacity of O'Neill > Mist > Ladder railings > Baldwin,and the characteristics of organ enrichment were presented as old leaf > fresh leaf > fruit.The content of manganese in the leaves and fruits of the four varieties of blueberry increased significantly with the decrease of altitude.The anthocyanins,soluble sugars and soluble proteins in the fruits of four blueberry varieties increased when treated by low concentrations of manganese(?1000mg·kg-1),and the content of soluble sugar,soluble protein and anthocyanin in the fruits of O'Neill and Mist varieties(?1000mg·kg-1)were not significantly decreased under high concentrations of manganese,indicating that the Mist and O'Neal varieties have relatively strong manganese tolerance.?3?Through indoor hydroponics test,the responses of fresh weight and dry weight to manganese toxicity were more sensitive than root in Mist and O'Neill varieties.The root growth of the seedlings of two varieties was promoted by low concentration of manganese(?1.0mg·L-1,T3),but was significantly inhibited by high concentration of manganese(?2.5mg·L-1,T4,T5).The root tolerance index?TI?of blueberries varieties was both greater than 0.5,with the pattern of TI o'neill >TI mist.The young plants of the two blueberry varieties had strong enrichment ability to manganese at each concentrations of manganese,and the manganese content in roots,stems and leaves was significantly positive correlation with manganese concentration?O'Neill: rroot=0.852,rstem=0.705,rleaf=0.883,P<0.01;Mist: rroot=0.652,rstem=0.813,rleaf=0.848,P<0.05?.?4?The manganese content of O'Neill and Mist varieties were mainly accumulated in their stem when treated by low concentration of manganese(?1.0 mg·L-1,T3).However,two blueberry varieties adopted different anti-manganese mechanisms when treated by high concentrations of manganese(?2.5mg·L-1,T4 and T5).Mist variety could reduce the toxicity of manganese ions to the ground through root interception,but O'Neill variety might weaken the manganese ion to the plant leaf mainly through the stem retention.?5?Under manganese stress,the physiological metabolic indices including malonaldehyde,proline and antioxidant enzyme activity were significantly different between O'Neill and Mist varieties.The CAT and POD enzyme activities of O'Neill cultivars increased significantly with manganese concentration,suggesting that CAT and POD enzymes may be the main defensive substances.Hence,it is suggested that O'Neal blueberries variety should better be selected and planted in flat terrain for reducing the probability of manganese toxicity in Nanling blueberry planting base. |
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