外源ABA提高甘蓝型油菜抗镉胁迫能力和氮素生理利用效率

  【目的】  植物脱落酸 (ABA) 可调节植物生长、种子休眠和叶片衰老，还可对非生物胁迫作出反应。比较添加外源ABA前后镉 (Cd) 胁迫下甘蓝型油菜的生理反应，可深化对脱落酸提高作物抗性和氮素生理利用效率作用机理的认识。  【方法】  供试甘蓝型油菜品种为814号，试验设3个处理:正常培养 (CK)、10 μmol/L CdCl₂ (Cd) 和5 μmol/L ABA + 10 μmol/L CdCl₂ (A + Cd)。在处理4天后，观察甘蓝型油菜表型，测定脯氨酸及丙二醛 (MDA) 含量、Cd含量、硝酸盐和铵盐含量以及硝酸还原酶 (NR)、谷氨酰胺合成酶 (GS) 活性等相关指标。  【结果】  与Cd处理相比，A + Cd处理甘蓝型油菜新叶SPAD值提高了1.1倍，根部脯氨酸含量增加了29.0%，MDA 含量降低了48.3%。外源ABA的添加会抑制甘蓝型油菜对Cd的吸收，降低甘蓝型油菜地上部和地下部Cd含量，减小Cd对甘蓝型油菜的毒害作用，影响甘蓝型油菜对NO₃–的吸收，降低油菜体内的总氮含量。与Cd处理相比，A + Cd处理甘蓝型油菜根部NR活性显著提高82.8%，更多的NH₄+分配到了地上部，地上部GS活性升高了32.1%，增强了甘蓝型油菜体内的氮同化和代谢过程，氮素生理利用效率显著提高了17.2%。  【结论】  外源ABA的添加可降低Cd的吸收量，提高氮代谢相关酶活性，促进脯氨酸的合成和降低丙二醛的生成，进而增强甘蓝型油菜对Cd的抗性，增强甘蓝型油菜体内氮同化和代谢的过程，并提高甘蓝型油菜的氮素生理利用效率。

Exogenous abscisic acid improves resistance to cadmium stress and physiological nitrogen use efficiency in Brassica napus

  【Objectives】  Abscisic acid (ABA) is capable of regulating plant growth, seed dormancy and leaf senescence, decreasing response to different abiotic stresses. We studied the response difference of B. napus to Cd stress under different ABA supplying levels, to increase the knowledge of ABA in regulating the physiological process and N nutrient.  【Methods】  The B. napus (No. 814) was treated under three circumstances: normal culture (CK), 10 μmol/L CdCl₂ (Cd), 5 μmol/L ABA + 10 μmol/L CdCl₂ (A + Cd). After 4 days of treatment, the phenotypes, proline and MDA content, Cd concentration, NO₃– and NH₄+ concentration, as well as NR and GS activities of B. napus were measured.  【Results】  Compared with Cd treatment, the SPAD value of B. napus new leaves in A + Cd was increased by 1.1 times, the proline concentration in the roots increased by 29.0%, and the malondialdehyde concentration decreased by 48.3%. The addition of exogenous ABA inhibited the absorption of cadmium in B. napus, decreased the Cd concentration in the shoots and roots, reduced the toxic effect of cadmium on B. napus, and also affected the absorption of NO₃– in B. napus and reduced the total N concentration in B. napus. Compared with Cd treatment, the addition of ABA significantly increased the NR activity in the roots of B. napus by 82.8%, enhanced the distribution of NH₄+ to the shoots, and the activity of GS in the shoots increased by 32.1%, which stimulated the N assimilation and metabolism in B. napus, and the physiological nitrogen use efficiency increased significantly by 17.2%.  【Conclusions】  The addition of exogenous ABA can reduce the absorption of Cd, increase the enzyme activities related to nitrogen metabolism, promote the synthesis of proline and decrease the production of malondialdehyde, thereby enhance the resistance of B. napus to Cd, and enhance the nitrogen assimilation and metabolism in B. napus, and increase the nitrogen use efficiency as well.