铝诱导黑麦的根尖分泌有机酸

虽然较多的研究已发现黑麦对铝毒害的忍耐能力较强，但是有关黑麦对铝毒害的抵御机理的报告很少。为了阐明黑麦（品种：King)对铝毒害的抵御机理，本研究探讨了黑麦的根系有机酸分泌的特性及其作用，铝能够诱导黑麦的根系分泌柠檬酸和苹果酸。柠檬酸主要从距顶端0－5mm的根尖分泌。有机酸的分泌量随着处理的铝浓度(0,50,100,300μmol/L AlCl3）和处理的时间（0．5，1，3，5h）的增加而增加。0，50，100，300μmol/L的AlCl3处理根尖3h后，从根尖分泌的柠檬酸和残留在根尖中的柠檬酸之和随着处理的铝浓度的增加而增加，而各处理间的苹果酸总量无显著差异。50μmol/L的柠檬酸或者400μmol/L的苹果酸能够消除50μmol/L 的AlCl3铝对小麦（Scout 66)根尖表面细胞的伤害。这些结果表明，铝促进柠檬酸的合成和柠檬酸、苹果酸从根尖的分泌是黑麦抵抗铝毒害的机理。     

The effects of Fe deficiency on low molecular weight organic acid exudation and cadmium uptake by Solanum nigrum L.

Abstract

The influence of Fe-deficiency on the root exudation of low molecular weight organic acids (LMWOAs), pH alteration and cadmium (Cd) accumulation and translocation were investigated in morel (Solanum nigrum L.) in hydroponic culture experiments. Tartaric, citric, malic and acetic acids were monitored because these acids were abundant and often detected as root exudates. Results showed that Fe-deficient plants excreted large amounts of LMWOAs in comparison with Fe-sufficient plants across all Cd treatments (p <0.05). In both cases the concentrations of the four organic acids were tartaric > citric > malic > acetic. The results showed that the Fe-deficient plants with higher concentrations of LMWOAs accumulated more Cd (p <0.05) and induced a decrease in solution pH compared with the Fe-sufficient plants. Cadmium accumulation in the Fe-deficient and Fe-sufficient plants had significant positive correlations with the exudation of malic and acetic acids (p <0.05 and p<0.01). Cadmium accumulation in the Fe-sufficient plants had a significant (p<0.01) positive correlation with the exudation of tartaric acid, whereas there was a negative correlation (p<0.01) between Cd accumulation and the exudation of tartaric acid in the Fe-deficient plants. No significant correlation between the exudation of citric acid and Cd accumulation was obtained. Our results indicate that Fe-deficiency could induce Cd accumulation and translocation through an increase of LMWOAs exudation and pH alteration, both of which enhance Cd bioavailability.     

Comparative Efficacy of White Mustard (Sinapis alba L.) and Soybean (Glycine max L. Merr.) Seed Meals as Bioherbicides in Organic Broccoli (Brassica oleracea Var. Botrytis) and Spinach (Spinacea oleracea) Production

White mustard and soybean seed meals were compared for weed control and yield of organically grown broccoli and spinach. The meals were incorporated into the soil 2 weeks before crop planting at two rates (1.24 and 4.48 t ha^?1). Weed densities and hand-weeding time were recorded twice during the growing seasons and weed biomass was measured at crop harvest. Compared to the 1.24 t ha^?1 soybean treatment, weed densities were 52 to 95% and 41 to 45% less at 3 and 6 weeks after planting, respectively, in both crops with the 4.48 t ha^?1 white mustard seed meal treatment. Time required for hand weeding at these times was also reduced by up to 82% and 48%, respectively. Broccoli yield was similar in all the treatments, but spinach yield was greatest in the 4.48 t ha^?1 treatments for both seed meals. Petiole nitrate and nutrient concentrations in both crops were generally similar in all the treatments.     

铝胁迫下黑麦根尖分泌有机酸和钾离子的研究

采用药理学研究方法,研究了几种抑制剂和脱落酸对铝诱导黑麦根尖分泌有机酸和钾离子的影响。结果表明,在铝(100、200、300μmol/L AlCl3)胁迫下,根尖分泌柠檬酸、苹果酸和钾离子,且随着铝处理浓度的增加其分泌量显著增加。阴离子通道抑制剂苯甲酰甲醛(0.1、0.2 mmol/L)抑制根尖在铝(200μmol/L AlCl3)胁迫下分泌有机酸的同时,也抑制根尖分泌钾离子;钾离子通道抑制剂四乙基铵(20、40 mmol/L)和铯(10、20 mmol/L CsCl)在抑制根尖分泌钾离子的同时,也抑制铝诱导的有机酸分泌。25、50μmol/L的ABA处理后,铝诱导的有机酸分泌和钾离子的分泌均显著增加。但是,铝诱导的有机酸分泌在受到阴离子通道抑制剂尼氟灭酸(0.4、0.8 mmol/L)处理抑制后,钾离子的分泌并不减少;铝胁迫下根尖分泌的钾离子在ATP酶抑制剂钒酸钠(0.25、0.50、2.00 mmol/L)处理后受阻的同时,有机酸的分泌却显著增加。这些结果说明,钾离子是铝诱导黑麦根尖分泌有机酸的陪伴离子,而并非有机酸分泌的调控因子。     

Benefits of Biochars and NPK Fertilizers for Soil Quality and Growth of Cowpea (Vigna unguiculata L. Walp.) in an Acid Arenosol

Fertilization is required for optimum plant growth, particularly in unfertile soils, while optimizing nutrient use efficiency is an alternative to reduce inorganic fertilizer needs and reduce environmental problems caused by nutrient leaching. This study investigated soil properties and cowpea yield responses to biochars (BCs) made from different feedstocks, baby corn peel biochar (BC1), branches of mango tree biochar (BC2), and rice husk biochar (BC3), applied in combination with nitrogen-phosphorus-potassium (NPK) fertilizers. The experiment was conducted in a greenhouse, using an acid sandy soil (Arenosol) that was submitted for 70 d to the following eight treatments:i) control; ii) full dose of NPK (a commercial compound fertilizer (12-24-12 of N-P₂O₅-K₂O) + urea (46% N)); iii) BC1 + half dose of NPK; iv) BC1 + full dose of NPK; v) BC2 + half dose of NPK; vi) BC2 + full dose of NPK; vii) BC3 + half dose of NPK; and viii) BC3 + full dose of NPK. All biochars were applied at a rate of 0.9% (weight/weight), and each type of biochar was combined with half and full doses of NPK fertilizers. Soil pH increased significantly (P < 0.05) in treatments with BC1 and BC2, while cation exchange capacity (CEC) and available P were higher in the treatments with BC1; BC1 and BC2 also induced higher activity of enzymes related to the P cycle and higher cowpea yield. Similar soil properties and cowpea yield parameters were obtained with the full and half doses of NPK fertilizers for each type of biochar used. In conclusion, biochars in the combination with NPK fertilizers improved soil chemistry and enzymatic activities, allowing reduced fertilizer application and food production costs in the acid soil studied.