Physiological and antioxidant changes in sunflower seeds under water restriction

Abstract: Seed vigor may be determinant for field performance, especially under water restriction conditions. Sunflower is a crop subject to these conditions in the field and, therefore, the aim of this study was to evaluate the physiological and antioxidant changes in sunflower seeds under water restriction. Two lots of sunflower seeds (cv. Hélio 253) with different vigor levels were used. After initial characterization, seeds were placed to germinate under water potentials of 0.0, -0.2, -0.4, -0.6 and -0.8 MPa and evaluated by tests of germination, first germination count, shoot length and primary root length. The activities of the antioxidant enzymes SOD, CAT, POX and APX were also evaluated at 0, 2, 4 and 6 days after sowing. Water restriction led to a decrease in germination and slower seedling growth, regardless of seed vigor level. SOD activity was similar in the two lots, with reduction in activity four days after sowing. CAT activity was affected differently during germination in the two lots, and it was generally higher in the most vigorous lot. In higher vigor seeds, there was lower POX activity in water restriction treatments compared to the control. In general, seeds of lower vigor have lower capacity for activation of antioxidant enzymes, especially peroxidases.

摘要：种子活力或许是决定作物田间表现的关键因素，在水分受限条件下尤为如此。向日葵是一类在田间易遭遇此类水分受限条件的作物，因此本研究旨在探究水分受限条件下向日葵种子的生理与抗氧化变化。本研究使用了两批活力水平存在差异的向日葵种子（cv. Hélio 253）。完成初始特性表征后，将种子置于水分势分别为0.0、-0.2、-0.4、-0.6与-0.8 MPa的环境中萌发，并通过发芽试验、初次发芽计数、芽长与初生根长测定对其进行评估。本研究还在播种后0、2、4、6天测定了抗氧化酶超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POX）与抗坏血酸过氧化物酶（APX）的活性。无论种子活力水平如何，水分受限均会降低发芽率并延缓幼苗生长。两批种子的SOD活性初始水平相近，且均在播种后第4天出现活性下降。两份种子在萌发过程中CAT活性受到的影响存在差异，高活力种子的CAT活性整体更高。相较于对照组，高活力种子在水分受限处理中的POX活性更低。总体而言，低活力种子激活抗氧化酶的能力更弱，尤其是过氧化物酶。