种子大小对旱地小麦种子萌发、幼苗特性和抗旱性的影响
Effects of Seed Sizes on Seed Germination, Seedling Characteristics and Drought Resistance of Dryland Wheat
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收稿日期: 2024-03-18 修回日期: 2024-05-15 网络出版日期: 2025-01-13
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Received: 2024-03-18 Revised: 2024-05-15 Online: 2025-01-13
作者简介 About authors
黄明,研究方向为旱地节水农业和高产栽培理论与技术,E-mail:
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In order to investigate the effects of seed sizes on seed germination, seedling root traits and leaf physiological characteristics and drought resistance of wheat, a hydroponic experiment was conducted. Large grain (> 6-mesh sieve, particle size > 3.35 mm), medium grain (6-8-mesh sieve, particle size 2.36-3.35 mm) and small grain (< 8-mesh sieve, grain size < 2.36mm) of Luohan 6 and Luohan 22 were selected and used as materials. Two water levels of 20% PEG-6000 simulated drought for T treatment and normal water supply for CK were conducted under hydroponic condition. The characteristics of seed germination, and the root characteristics, antioxidant enzyme system and osmotic regulation substances in seedlings at 3, 6, and 9 days after treatments were determined. The results showed that the germination potential and germination rate of large seeds were significantly increased by 7.2% and 12.4% for Luohan 22 under T treatment, and 42.0% and 36.7% for Luohan 6 under CK, but there was no significant advantage in medium seeds compared with small seeds. Compared with small seeds, the root activity of large seeds of Luohan 6 under drought and control all increased at three and six days after treatment, but there was no significant difference in Luohan 22. With the increase of seed size, the root length, root surface area, root volume, the number of root tips and branches increased significantly; and the activities of superoxide dismutase (SOD) and catalase (CAT) and the content of soluble sugar (SS) in seedling leaves showed an increasing trend, while the content of malondialdehyde (MDA) and free proline (Pro), showed a decreasing trend. Compared with small seeds, the SOD activity of large seeds under T treatment was significantly increased, the CAT activity under CK and the content of SS under T treatment was increased in Luohan 6, and the MDA and Pro contents of Luohan 22 under CK were all decreased; Compared with medium and small seeds, the comprehensive drought resistance coefficients of the two wheat varieties were all increased. Overall, large seeds have major advantages in terms of germination, seedling roots, and stress resistance; however, the impacts differed based on drought stress, variety, and measurement indexes. Screening and planting large-size seeds is beneficial for improving the germination of dryland wheat seeds and the indexes of seedling development.
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本文引用格式
黄明, 付鑫鑫, 张振旺, 张军, 李友军.
Huang Ming, Fu Xinxin, Zhang Zhenwang, Zhang Jun, Li Youjun.
种子大小作为良种的一个重要特性,直接关系着种子萌发和幼苗的生长发育[3]。大粒种子由于贮藏了较多的营养物质,不仅在逆境环境条件下对资源的竞争能力强[3],而且具有较强生长势[4-5],特别是在种子萌发和幼苗生长过程中作用突出。研究[3-4,7]普遍表明,种子大小与幼苗重量呈显著正相关,而与相对生长率呈负相关。刘斌祥等[5]研究表明,大、中粒玉米种子不仅萌芽率和出苗率高,且活跃破土、出苗期短,出苗整齐度较高,利于苗全、苗齐和苗匀。陈思晓等[6]研究发现,以千粒重为标准将煤生0308和烟农19种子大小分为8个粒级,幼苗根长、根数量、有机物含量随着粒重的增加而增加。马秀云等[7]根据千粒重将60个小麦品种分为3种不同粒重类型,发现幼苗总根长、根鲜重均表现为大粒重>中粒重>小粒重,且不同类型间差异均显著。刘生祥等[8]研究也表明,种子大小与植物生长势密切相关,大粒种子具有促进幼苗分蘖、抗逆性强、营养生长旺盛和增产的潜力。毛思帅等[9]研究表明,与小粒小麦种子相比,大粒小麦种子(粒径>3.35 mm)和中粒小麦种子(粒径2.36~3.35 mm)分别增产540和431 kg/hm2,增产5.5%和6.9%。这些结果表明,种子大小可以影响作物发芽、根系和幼苗建植等特性,进而影响产量的形成。然而,目前有关种子大小影响小麦幼苗生理特性的研究较少,特别是种子大小与旱地小麦抗旱性之间的关系尚未见报道。因此,本研究以洛旱6号和洛旱22大、中、小3种粒径种子为材料,通过PEG-6000模拟干旱和正常供水对照的室内水培试验,研究种子大小对旱地小麦种子萌发特性,幼苗根系性状和叶片生理特性的影响,并评价其对干旱的响应,为旱地小麦品种的筛选和推广种植提供理论依据。
1 材料与方法
1.1 供试材料
供试品种为洛旱6号和洛旱22,均为河南省洛阳市农林科学院选育的旱肥地品种。其中,洛旱6号(国审麦2006020)选自父母本组合豫麦49号/山农45,株高80 cm,抗旱性达3级,抗旱性中等,在2015年创造并保持多年9808.5 kg/hm2(亩产653.9 kg)的全国旱地小麦高产纪录。洛旱22(国审麦20180058)选自父母本组合周麦16/洛旱7号(洛旱7号选自父母本组合豫麦41号/山农45),株高74.9 cm,抗旱性达3级,抗旱性中等,与晋麦47相当;2022年创造了9892.8 kg/hm2(亩产659.52 kg)的纪录。
参照毛思帅等[9]描述的方法用种子筛区分不同种子(粒径)大小,分为大粒Ⅰ(>6目筛,粒径>3.35 mm)、中粒Ⅱ(6~8目筛,粒径2.36~3.35 mm)和小粒Ⅲ(<8目筛,粒径<2.36 mm)。
1.2 试验设计
1.2.1 种子萌发特性
试验于2019年10-11月在河南科技大学农学院实验室进行。将2个品种各粒径籽粒用75%酒精消毒10 min后用蒸馏水冲洗干净,吸涨24 h后,挑选露白的种子。将种子腹股沟向下放在铺有2层滤纸的发芽盒(10 cm×10 cm×3 cm)中,每盒70粒、均匀摆放,对应加入预设溶液15 mL,3次重复。预设溶液分别为1/2 Hoagland营养液配制而成的20% PEG-6000溶液,用于模拟干旱[10],用T表示,不添加PEG-6000的1/2 Hoagland营养液作为对照,用CK表示。随后放入20 ℃恒温培养箱,设置湿度85%,光周期昼/夜12 h/12 h,光强10 000 lx。
1.2.2 幼苗根系和生理特性
种子处理同1.2.1。吸涨24 h后,挑选露白的种子,用海绵固定到泡沫板上,放入水培篮中(15 cm×20 cm×15 cm)进行培养。为模拟根系生长的黑暗环境,水培篮四周用黑色胶带包裹。每个水培篮添加2.0 L的1/2 Hoagland营养液,每2 d更换1次营养液。培养至3叶1心进行水分处理(T处理和CK处理),3次重复。整个试验过程用气泵维持溶液氧浓度(DO)为6~8 mg/L。
1.3 测定项目与方法
1.3.1 种子活力
根据《国家种子检验规程》,以胚根长≥种子长或胚芽长≥0.5倍种子长作为发芽标准,在第3天测定发芽势,在第7天测定发芽率[11]。
发芽势(%)=第3天发芽种子粒数/供试种子粒数×100;
发芽率(%)=第7天发芽种子粒数/供试种子粒数×100。
1.3.2 根系指标
在处理后的3、6和9 d分别从每个处理中采集幼苗根系5条,用蒸馏水洗净后用吸水纸吸干,采用氯化三苯基四氮唑还原法(TTC法)测定根系活力[12]。在处理后4和8 d从每个处理中分别采集小麦苗5株,先用蒸馏水洗净后用滤纸将其表面水分吸干,放在玻璃盘上用镊子小心将每条根展开,使根与根之间不交叉、不重叠,再用根系扫描仪(Epson EU-88)进行扫描,扫描后采用Win-RHIZO系统分析根长、根直径、根表面积和根体积。
1.3.3 生理指标
在水分处理后的3、6和9 d,分别从每个处理中取5个叶片,剪碎混匀后用于测定超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性及丙二醛(MDA)、可溶性糖(SS)和游离脯氨酸(Pro)含量。采用氮蓝四唑(NBT)法测定SOD活性,采用紫外线吸收法测定CAT活性,采用硫代巴比妥酸法(TBA)测定MDA含量,采用蒽酮比色法测定SS含量,采用酸性茚三酮法[13]测定Pro含量。
1.3.4 抗旱系数
抗旱系数(DC)=干旱处理测定值/对照测定值[14]。
1.4 数据处理
采用Microsoft Excel 2016和SPSS 27对数据进行处理。采用单因素方差分析法(one-way ANOVA)和最小显著差异法(LSD)分析不同种子大小和不同水分处理间各参数的差异。采用Microsoft Excel 2016作图。
2 结果与分析
2.1 不同处理对种子发芽势和发芽率的影响
由表1可知,与对照相比,T处理使洛旱6号和洛旱22不同粒径的种子发芽势和发芽率均显著降低,洛旱6号的发芽率和发芽势均高于洛旱22。随着种子粒径的增加,小麦发芽势和发芽率总体呈上升趋势,但影响效应因品种和干旱与否而异。与小粒种子相比,大粒种子T处理下洛旱22的发芽势和发芽率分别显著提高7.2和12.4个百分点,但洛旱6号无显著变化;CK处理下洛旱6号的发芽势和发芽率分别显著提高41.0和36.7个百分点,但洛旱22无显著变化。与小粒种子相比,中粒种子除洛旱6号的发芽势和发芽率在对照下显著提高外均无显著差异。说明大粒种子能在干旱下提高洛旱22的发芽势和发芽率。
表1 种子大小对小麦发芽势和发芽率的影响
Table 1
品种 Variety | 种子大小 Seed size | 发芽势Germination potential | 发芽率Germination rate | |||
---|---|---|---|---|---|---|
T | CK | T | CK | |||
洛旱6号Luohan 6 | Ⅰ | 30.00±3.78Aa | 81.90±4.12Ab | 58.57±5.15Aa | 92.86±2.86Ab | |
Ⅱ | 25.71±5.71Aa | 74.76±7.33Ab | 51.90±3.30Aa | 86.67±4.36Bb | ||
Ⅲ | 23.81±1.65Aa | 40.95±3.30Bb | 41.90±3.60ABa | 56.19±0.82Cb | ||
洛旱22 Luohan 22 | Ⅰ | 38.57±2.86Aa | 59.52±4.36Ab | 57.14±1.43Aa | 85.71±1.43Ab | |
Ⅱ | 28.57±7.14Ba | 54.29±8.92Ab | 40.95±8.61Ba | 80.95±6.75Ab | ||
Ⅲ | 31.40±2.86Ba | 52.38±5.02Ab | 44.70±7.87Ba | 82.86±2.47Ab |
不同大写字母表示同一测定时期同一处理下不同种子大小间差异显著;不同小写字母表示同一测定时期同一种子大小不同处理间差异显著(P < 0.05)。下同。
Different capital letters indicate significant differences in seed sizes under the same treatment in the same measuring period, and different lowercase letters indicate significant differences between different treatments in the same measuring period (P < 0.05). The same below.
2.2 不同处理对幼苗根系特性的影响
2.2.1 对幼苗根系活力的影响
由图1可知,随着种子粒径的增加,小麦幼苗根系活力总体呈上升趋势。与小粒种子相比,大粒种子和中粒种子在处理后不同天数下幼苗根系活力均显著增加。处理后3、6、9 d,与小粒种子比,干旱下洛旱6号大粒种子显著提高15.4%~37.4%,对照下提高20.1%~41.2%,中粒种子干旱下提高3.6%~22.8%,对照下提高7.3%~27.1%;洛旱22大粒种子干旱下提高12.7%~135.9%,对照下提高15.9%~47.5%,中粒种子分别提高4.0%~20.7%和7.6%~74.8%,洛旱22的最高增幅多高于洛旱6号。说明大粒与中粒种子都有提高根系活力的作用,且大粒种子和洛旱22的优势突出。
图1
图1
种子大小对小麦幼苗根系活力的影响
不同大写字母表示同一测定时期同一处理下不同种子大小间差异显著;不同小写字母表示同一测定时期同一种子大小不同处理间差异显著(P < 0.05)。下同。
Fig.1
Effects of seed size on root activity of wheat seedlings
Different capital letters indicate significant differences in seed sizes under the same treatment in the same measuring period; different lowercase letters indicate significant differences under different treatments under the same seed size in the same measuring period (P < 0.05). The same below.
2.2.2 对幼苗根系特性的影响
由表2可知,与对照相比,干旱使冬小麦幼苗根长、根表面积、根直径、根体积、根尖数和根分枝数均显著降低。随着种子粒径的增加,上述指标均呈增加趋势,且除根直径外,大、中、小粒种子间各根系参数的差异均达到显著水平。说明2个品种的大粒种子与中粒种子可改善幼苗的根系构型,且大粒种子优势更为显著。
表2 种子大小对小麦幼苗根系特性的影响
Table 2
指标 Index | 处理 Treatment | 天数 Days (d) | 洛旱6号Luohan 6 | 洛旱22 Luohan 22 | |||||
---|---|---|---|---|---|---|---|---|---|
Ⅰ | Ⅱ | Ⅲ | Ⅰ | Ⅱ | Ⅲ | ||||
总根长 Total root length (cm) | T | 4 | 335.6±4.2Ab | 208.3±9.4Bb | 152.4±13.6Cb | 289.5±20.4Ab | 190.8±12.7Bb | 128.0±16.4Cb | |
8 | 454.2±16.3Ab | 347.0±21.2Bb | 201.7±5.7Cb | 417.6±13.0Ab | 299.6±22.6Bb | 212.6±5.7Ca | |||
CK | 4 | 557.4±8.4Aa | 406.9±4.9Ba | 314.2±12.6Ca | 457.5±26.4Aa | 370.3±15.1Ba | 257.5±6.0Ca | ||
8 | 759.4±15.0Aa | 573.8±47.0Ba | 392.8±11.0Ca | 558.8±23.7Aa | 462.2±18.5Ba | 291.5±47.3Ca | |||
总根表面积 Total root surface area (cm2) | T | 4 | 27.3±1.6Ab | 17.7±0.8Bb | 13.8±0.2Cb | 28.6±2.3Ab | 16.7±0.6Bb | 10.2±1.3Cb | |
8 | 40.2±1.1Ab | 34.4±3.3Bb | 20.4±0.3Cb | 39.9±4.1Aa | 28.6±3.0Ba | 21.1±1.0Ca | |||
CK | 4 | 40.8±2.3Aa | 30.1±0.9Ba | 24.4±2.6Ca | 33.9±0.6Aa | 28.0±0.7Ba | 20.7±1.7Ca | ||
8 | 56.0±5.1Aa | 45.0±4.2Ba | 30.2±1.8Ca | 47.8±3.1Aa | 35.7±4.4Ba | 23.3±5.1Ca | |||
根直径 Root diameter (mm) | T | 4 | 0.32±0.03Aa | 0.30±0.03Aa | 0.28±0.01Aa | 0.28±0.02Aa | 0.29±0.02Aa | 0.25±0.02Aa | |
8 | 0.33±0.00Aa | 0.30±0.01Ba | 0.27±0.01Ca | 0.33±0.02Aa | 0.28±0.01Ba | 0.32±0.02Aa | |||
CK | 4 | 0.25±0.01Ab | 0.23±0.01Ab | 0.23±0.01Ab | 0.26±0.00Aa | 0.26±0.01Aa | 0.23±0.01Ba | ||
8 | 0.23±0.02Ab | 0.25±0.01Ab | 0.23±0.00Ab | 0.26±0.01Ab | 0.26±0.01Aa | 0.23±0.01Bb | |||
总根体积 Total root volume (cm3) | T | 4 | 0.18±0.03Aa | 0.13±0.02Ab | 0.13±0.03Aa | 0.20±0.03Aa | 0.14±0.03Aa | 0.07±0.01Bb | |
8 | 0.29±0.00Ab | 0.25±0.01Ba | 0.16±0.01Ca | 0.33±0.03Aa | 0.20±0.02Ba | 0.17±0.02Ba | |||
CK | 4 | 0.24±0.02Aa | 0.17±0.01Ba | 0.15±0.03Ba | 0.20±0.02Aa | 0.15±0.02Ba | 0.15±0.02Ba | ||
8 | 0.36±0.02Aa | 0.28±0.03Ba | 0.19±0.02Ca | 0.32±0.03Aa | 0.23±0.03Ba | 0.15±0.03Ca | |||
总根尖数Total root tips | T | 4 | 460.3±44.1Ab | 385.7±8.7ABb | 318.3±50.7Ba | 445.0±77.5Ab | 292.7±38.0Bb | 230.3±30.2Bb | |
8 | 1076.0±9.4Ab | 703.3±163.6Ba | 473.0±137.3Ba | 1009.0±20.2Ab | 592.3±215.5Ba | 349.7±36.7Bb | |||
CK | 4 | 919.7±38.6Aa | 728.3±26.6Ba | 431.3±53.1Ca | 725.3±56.6Aa | 611.7±26.2Aa | 460.3±58.0Ba | ||
8 | 1562.7±87.2Aa | 978.0±88.8Ba | 766.3±110.6Ba | 1471.0±84.1Aa | 950.3±155.3Ba | 674.0±21.7Ca | |||
根分枝数 Number of root branches | T | 4 | 909.3±71.3Ab | 564.7±65.2Bb | 402.0±136.1Ba | 656.3±32.2Ab | 467.3±73.7Bb | 399.0±55.1Ba | |
8 | 1849.3±49.8Aa | 1151.3±90.4Bb | 510.3±43.7Cb | 1388.3±128.4Ab | 1172.7±105.8Aa | 659.7±115.6Ba | |||
CK | 4 | 1469.0±126.9Aa | 1010.3±7.6Ba | 606.3±62.5Ca | 1150.0±122.5Aa | 805.0±66.6Ba | 490.7±57.2Ca | ||
8 | 2639.0±525.2Aa | 1915.0±316.1ABa | 1154.7±64.4Ba | 1835.0±37.5Aa | 1485.7±247.2Aa | 829.3±110.8Ba |
2.3 种子大小对幼苗抗氧化特性的影响
由图2可以看出,干旱较对照使各粒径种子的幼苗叶片SOD、CAT活性均显著降低,MDA含量显著升高。随着种子粒径的增加,幼苗叶片SOD、CAT活性上升,但影响效应与品种和干旱与否有关。与小粒种子相比,大粒种子幼苗叶片SOD活性对照下洛旱6号在处理后3、6和9 d分别显著提高11.0%、60.7%和21.1%,而干旱下洛旱22分别显著提高81.1%、99.2%、63.0%;不同水分条件和品种下幼苗叶片CAT活性均表现为显著提高,幼苗叶片MDA含量均降低。中粒种子与小粒种子相比,幼苗SOD和CAT活性大部分无显著增加,幼苗MDA含量除对照下洛旱6号处理后9 d、洛旱22处理后3 d显著降低外也无显著变化。说明大粒种子会提高幼苗SOD和CAT活性,抗逆能力强,降低MDA含量,降低膜脂过氧化程度,且洛旱22 SOD活性的提高幅度大于洛旱6号,但中粒种子的效果并不突出。
图2
图2
种子大小对小麦幼苗叶片SOD、CAT活性和MDA含量的影响
Fig.2
Effects of seed size on SOD, CAT activities and MDA contents in wheat seedling leaves
2.4 种子大小对幼苗渗透调节物质含量的影响
由图3可知,与对照相比,干旱胁迫下2个品种各粒径种子的幼苗SS含量降低,但Pro含量升高。与小粒种子相比,干旱和对照处理洛旱6号大粒种子幼苗的SS含量分别显著提高38.0%~ 58.0%和37.9%~53.2%,洛旱22分别显著提高27.7%~34.0%和30.7%~71.1%。与小粒种子相比,中粒种子幼苗SS含量仅对照下洛旱6号处理后 d和洛旱22处理后9 d时表现为显著提高。由图3还可以看出,洛旱6号的幼苗Pro含量多高于洛旱22。与小粒种子相比,大粒种子在干旱和对照处理下洛旱6号幼苗Pro含量分别降低13.8%~ 49.9%和30.3%~49.9%,洛旱22分别显著降低30.9%~53.5%和40.4%~73.6%。与小粒种子相比,中粒种子幼苗Pro含量洛旱6号降低不显著,但洛旱22干旱下处理后3、6 d和对照下处理后6 d分别降低31.0%、31.2%和64.4%。说明大粒种子会提高幼苗SS含量,降低Pro含量,且洛旱22的中粒种子也有降低幼苗Pro含量的作用。
图3
图3
种子大小对小麦幼苗叶片SS和Pro含量的影响
Fig.3
Effects of seed sizes on SS and Pro contents in wheat seedling leaves
2.5 种子大小对小麦萌发期和幼苗期抗旱性的影响
表3结果表明,同一品种不同种子粒径间、不同指标间的抗旱系数和综合抗旱系数存在差异,不同指标间的抗旱系数介于0.13~5.27,总根体积抗旱系数最小,Pro含量抗旱系数最大,说明种子萌发以及幼苗根系和叶片特性对干旱胁迫的响应程度不同。大粒种子较小粒种子综合抗旱系数增大,说明冬小麦抗旱性随种子粒径的增加而增强,其中根体积的抗旱系数差异最大,与小粒种子相比,大粒种子洛旱6号和洛旱22分别提高64.8%和113.0%。此外,洛旱6号的根平均直径、根体积、根分枝数的抗旱系数,洛旱22的Pro含量、根系活力、发芽率、根体积和根尖数的抗旱系数提高,增幅均在20%以上。洛旱22综合抗旱系数大粒种子比中、小粒种子分别提高18.7%和17.7%,但洛旱6号差异不明显。
表3 种子大小对小麦萌发期和幼苗期抗旱系数和综合抗旱系数的影响
Table 3
指标Index | 洛旱6号 Luohan 6 | 洛旱22 Luohan 22 | |||||
---|---|---|---|---|---|---|---|
Ⅰ | Ⅱ | Ⅲ | Ⅰ | Ⅱ | Ⅲ | ||
发芽率Germination rate | 0.63 | 0.60 | 0.75 | 0.67 | 0.51 | 0.54 | |
发芽势Germination energy | 0.37 | 0.34 | 0.58 | 0.65 | 0.53 | 0.60 | |
根系活力Root activity | 1.25 | 1.18 | 1.20 | 1.45 | 1.43 | 1.12 | |
总根长度Total root length | 0.60 | 0.57 | 0.50 | 0.71 | 0.60 | 0.65 | |
总根表面积 Total root surface area | 0.74 | 0.68 | 0.63 | 0.88 | 0.61 | 0.78 | |
根直径Root diameter | 0.33 | 0.30 | 0.27 | 0.31 | 0.28 | 0.30 | |
总根体积Total root volume | 0.25 | 0.21 | 0.15 | 0.28 | 0.18 | 0.13 | |
总根尖数Total root tips | 0.63 | 0.66 | 0.66 | 0.66 | 0.58 | 0.51 | |
根分枝数 Number of root branches | 0.67 | 0.59 | 0.52 | 0.69 | 0.72 | 0.80 | |
SOD活性SOD activity | 0.69 | 0.83 | 0.73 | 0.79 | 0.58 | 0.69 | |
CAT活性CAT activity | 0.40 | 0.44 | 0.55 | 0.46 | 0.41 | 0.52 | |
MDA含量MDA content | 1.31 | 1.48 | 1.30 | 1.46 | 1.46 | 1.44 | |
SS含量SS content | 0.44 | 0.38 | 0.44 | 0.52 | 0.52 | 0.61 | |
Pro含量Pro content | 3.20 | 2.77 | 2.97 | 5.27 | 4.07 | 3.88 | |
综合抗旱系数 Comprehensive drought resistance coefficient | 11.51 | 11.02 | 11.24 | 14.80 | 12.47 | 12.57 |
3 讨论
3.1 种子大小对小麦种子活力和根系、幼苗生长的影响
种子是植物早期生长发育所需养分的主要来源,其大小会对种子萌发、根系发育和幼苗生长产生影响[16]。吴薇[17]研究发现,发芽率表现为中粒>大粒>小粒,发芽指数表现为中粒>小粒>大粒。周芳等[18]研究表明,大粒种子因贮藏营养物质多,幼苗生长旺、根系发达,这种优势随生育进程推进有减弱趋势,在较长的生育期内其根长、根表面积、根体积等均高于小粒种子。有研究[19-20]发现,大粒种子有利于作物生育前期的根系发育和生物量积累,促进幼苗建植,增强作物在生育中后期吸收利用水分和养分的能力。本研究发现,大粒和中粒种子可保持较大的根长、根表面积、根体积、根尖数和根分枝数,苗期苗壮,且大粒种子优势突出,可大幅改善种子萌发特性,这与前人研究结果一致。结果说明旱地小麦大粒种子利于种子萌发并改善根系幼苗特性。应大力推进旱地小麦种子粒径筛选,促进干旱胁迫下种子萌发、根系发育和幼苗建植,为后期的生长发育和高产奠定基础。
3.2 种子大小对小麦幼苗生理特性的影响
在干旱胁迫下,植物可通过提高抗氧化酶活性维持活性氧代谢平衡,以保护膜结构和功能的完整性[21-22]。MDA含量是用来反映膜脂质过氧化程度强弱的重要指标,其含量越高,说明组织的保护能力越弱[23]。本试验结果表明,干旱胁迫使幼苗根系和叶片的MDA含量明显增加,表现出了不同程度的膜脂过氧化。干旱下大粒种子的幼苗具有较高的SOD和CAT活性,MDA含量最低,表现出较强的清除体内活性氧能力,从而减小干旱胁迫伤害,维持正常的生长发育,且干旱下洛旱22的SOD活性提高幅度明显大于洛旱6号,表现出较强的清除自由基的能力。可溶性糖和脯氨酸是评价作物抗性的重要参数[24]。可溶性糖可保护蛋白质,对维持细胞膨压以及促进植物体内活性氧清除有重要作用,可提高植物在逆境胁迫下的耐性;脯氨酸是植物体内分布最广的渗透调节物质,一般而言,植物受旱会导致脯氨酸积累[25]。本试验结果表明,在干旱和对照下,大粒种子幼苗的SS含量均高于中、小粒种子,且降低了Pro含量,表现出了较强的渗透调节能力,洛旱22中粒种子较小粒种子也有效降低了幼苗Pro含量,表现出较强的抗旱能力。洛旱22幼苗叶片SOD活性和Pro含量上的优势,可能与其是洛旱6号的姐妹系洛旱7与丰产品种周麦16杂交所得,其抗旱性得到了进一步改良,但其机理还有待进一步研究。
3.3 种子大小对小麦抗旱性的影响
提高作物在干旱胁迫下的发芽、出苗和幼苗建植能力,是保证旱地作物群体的重要内容,这与种子的抗旱性有关。王威等[26]研究表明,大粒种子具有较强的抗旱性,植株内源保护酶SOD、CAT和POD活性增强。Lebrija-Trejos等[27]研究表明,大粒种子幼苗具有强的生长势、逆境耐受能力。闫兴富等[28]研究表明,大粒种子在生理活性方面具有优势,表现出更强的干旱耐受性。这些结果说明种子大小与作物的抗旱性有关,但目前没有从种子大小角度综合评价小麦抗旱性的研究。本研究分析不同种子大小萌发特性和根系幼苗生理特性抗旱性发现,与小粒种子相比,大粒种子根系特性的抗旱系数有明显规律,但有明显效应的指标因品种而异,洛旱6号为根平均直径、根体积和根分枝数,洛旱22为根系活力、发芽率、根体积和根尖数。此外,洛旱22还可以大幅提高幼苗叶片Pro的抗旱系数。分析综合抗旱系数表明,大粒种子具有较高综合抗旱系数,表现出了较强的抗旱性,特别是洛旱22的大粒种子较中、小粒种子的抗旱系数分别提高18.7%和17.7%,在旱作小麦条件下,洛旱22品种更应注重应用大粒种子。
4 结论
与小粒种子相比,大粒种子干旱下洛旱22、对照下洛旱6号利于提高发芽势和发芽率,但幼苗根系活力多无显著差异。随种子粒径的增加,幼苗根系特性得到显著改善,幼苗叶片SOD和CAT活性、SS含量提高,且MDA和Pro含量下降,因而明显提高了综合抗旱系数。与洛旱6号相比,洛旱22表现出一定的抗旱优势。因此,大粒种子利于改善旱地小麦发芽特性、幼苗根系和叶片抗旱生理特性,应在旱地小麦生产中加强应用。
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小麦品种内种子大小分级与种子质量的关系
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将小麦品种煤生0308和烟农19的千粒重分为8个粒级,测定分析不同粒级平均千粒重的差异,并分析平均千粒重、蛋白质含量、幼苗根长、根数、根干重、苗高、苗干重及粒级平均千粒重和蛋白质含量间的关系。结果显示,不同粒级间平均千粒重与其蛋白质含量、幼苗根长、根数、根干重、苗高、苗干重差异显著。各粒级平均千粒重差异幅度达10%以上,2个品种最小和最大粒级间分别相差达248.0%和173.0%;不同粒级间蛋白质含量差异显著,最小与最大粒级间相差幅度分别为9.2%和13.4%;苗鲜重和干重增加幅度最大,达到5倍左右;根长次之,增加1倍左右;根条数增加幅度最小,但2个品种也分别达到35.0%和21.4%;幼苗高度、鲜重和干重差异显著,同样也是随着粒级粒重的增加而增加,其中鲜重增加幅度最大为5倍,其次为干重增加3倍,不同粒级幼苗质量的差异趋势与粒重和蛋白质含量相一致。不同粒级种子的根长、根数、根干重、苗高、苗干重及与粒级平均千粒重、蛋白质含量间呈极显著正相关关系,煤生0308的相关系数分别达到0.933 9、0.954 3、0.957 8和0.954 6,烟农19分别为0.993 9、0.974 1、0.928 1和0.974 4,并呈现出极显著的正向线性关系。结果表明,品种内种子间的粒重、蛋白质含量、幼苗根长、根数、根干重、苗高、苗干重存在显著差异,幼苗根长、根数、根干重、苗高、苗干重与粒重和蛋白质含量之间存在着极显著的正向线性关系。利用品种内大粒优质种子,能够提高幼苗质量。
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在温室内遮阴条件下,设置80%、60%、40%和20%田间持水量(对照、轻度、中度和重度干旱)4个处理,研究种子大小和干旱胁迫对盆栽辽东栎幼苗生长和生理特性的影响。结果表明: 大种子(3.05±0.38 g)幼苗的单株叶面积、总干质量和根冠比在所有处理均显著大于小种子(1.46±0.27 g)幼苗,前者的株高、基径、叶片数、比叶面积、相对生长率和净同化率等生长参数在轻度、中度和重度干旱处理均不同程度大于后者。大种子幼苗叶片过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性均高于小种子幼苗,前者叶片丙二醛(MDA)、可溶性蛋白、游离脯氨酸含量和叶绿素总量在部分干旱处理显著大于后者。除根冠比外,其他生长参数均随干旱胁迫增强逐渐减小,重度干旱处理大、小种子幼苗总干质量分别比对照降低19.4%和20.0%。POD、CAT和SOD活性均随干旱胁迫增强先升后降,在中度干旱处理,大、小种子幼苗POD活性分别显著高于对照126.7%和142.1%,CAT活性分别显著高于对照170.0%和151.9%。在重度干旱处理,大、小种子幼苗MDA含量分别显著高于对照86.5%和68.9%。可溶性蛋白、游离脯氨酸含量和叶绿素总量均随干旱胁迫增强先升后降,在中度干旱处理,大、小种子幼苗可溶性蛋白含量分别显著高于对照320.7%和352.7%。辽东栎大种子幼苗可依赖其生长和生理方面的优势比小种子幼苗具有更强的干旱耐受性,在退化次生林人工辅助实生更新中应优先选用抗逆性更强的大种子幼苗。
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