高佳, 史建国, 董树亭, 刘鹏, 赵斌, 张吉旺^*
作物生物学国家重点实验室 / 山东农业大学农学院, 山东泰安 271018
^* 通讯作者(Corresponding author): 张吉旺, E-mail: jwzhang@sdau.edu.cn, Tel: 0538-8241485 第一作者联系方式: E-mail: gaoj0803@163.com, Tel: 15505385417
收稿日期:2016-12-06 接受日期:2017-05-10网络出版日期:2017-05-22基金:本研究由国家自然科学基金项目(31671629), 国家现代农业产业技术体系建设专项(CARS-02-20), 山东省农业重大应用技术创新项目和山东省玉米育种与栽培技术企业重点实验室开放课题资助

摘要为了探讨不同光照条件对夏玉米籽粒胚乳细胞增殖及产量的影响, 2012—2014年于山东农业大学试验农场进行了大田试验, 选玉米品种郑单958和登海605为试验材料, 设置大田自然光照(CK)、开花至收获期遮阴(S1)、拔节至开花期遮阴(S2)、出苗至收获期遮阴(S3)和开花至收获期增光(L) 5个处理, 研究其对夏玉米籽粒胚乳细胞增殖、籽粒灌浆、淀粉含量、干物质积累及产量的影响。结果表明, 遮阴后籽粒胚乳细胞增殖速率、细胞数目和淀粉积累量降低, 细胞充实度下降, 粒重显著降低, 且S3对其影响最大, S1次之, S2影响相对较小。郑单958和登海605两个品种S1、S2和S3成熟期的胚乳细胞数目较CK分别降低33%、6%、29%和41%、5%、29%, DH605 L处理显著提高了胚乳细胞增殖速率、胚乳细胞数目及淀粉含量, 细胞充实度和粒重显著上升。遮阴导致籽粒灌浆速率减缓, 灌浆高峰期推迟, 2个品种S1、S2和S3的最大灌浆速率较CK分别降低34%、13%、58%和38%、13%、64%, 登海605 L处理提高了籽粒灌浆速率, 籽粒灌浆高峰期提前出现。2个品种S1、S2和S3较CK分别减产58%、26%、81%和67%、27%、81%, 登海605 L处理增产9%。即遮阴降低了籽粒胚乳细胞数目、淀粉含量和灌浆速率, 进而影响产量, 花粒期充足的光照则有助于籽粒胚乳细胞增殖和产量提高。

关键词:夏玉米; 光照; 胚乳细胞增殖; 籽粒灌浆; 产量
Response of Endosperm Cell Proliferation and Grain Yield of Summer Maize to Different Light Conditions
GAO Jia, SHI Jian-Guo, DONG Shu-Ting, LIU Peng, ZHAO Bin, ZHANG Ji-Wang^*
State Key Laboratory of Crop Biology / Agronomy College of Shandong Agricultural University, Tai’an 271018, China
Fund:This study was supported by National Natural Science Funds (31671629), the China Agriculture Research System (CARS-02-20), Shandong Key Agricultural Technology Innovation Project and Shandong Provincial Key Laboratory of Corn Breeding and Cultivation Technology.
AbstractDuring the period from 2012 to 2014, Zhengdan 958 (ZD958) and Denghai 605 (DH605) were used with five treatments in a randomized complete block design with three replicates, including increasing light (L) from tassel stage (VT) to maturity stage (R6) and three shading treatments (40% of ambient light intensity) from VT to R6 (S1), from the sixth leaf stage (V6) to VT (S2), and from emergence stage (VE) to R6 (S3), and natural lighting in the field (CK). The illumination intensity of L on cloudy day was 1600-1800 μmol m^-2 s^-1. This experiment was conducted to explore the effects of light on endosperm cell proliferation, grain filling, starch content, dry matter accumulation and yield of summer maize. The dry matter accumulation of embryo and endosperm was significantly decreased under shading, as well as the content of starch and the endosperm cell plumpness decreased also. Effect of S3 on endosperm cell proliferation was the most, while that of S2 was the smallest. At R6, the endosperm cells number of S3, S2, S1 decreased by 33%, 6%, 29% in ZD958 and 41%, 5%, 29% in DH605. The dry matter accumulation of embryo and endosperm as well as the content of starch and the endosperm cell plumpness were increased after increasing light. The grain filling rate decreased and the days to maximum grain filling rate postponed under shading, while those increased after increasing light. The maximum grain filling rate of S1, S2, S3 decreased by 34%, 13%, 58% in ZD958 and 38%, 13%, 64% in DH605. The grain yield of S1, S2, S3 decreased by 58%, 26%, 81% in ZD958 and 67%, 27%, 81% in DH605. Results indicate that the number of endosperm cells, starch content and grain filling rate are decreased under shading, resulting in grain yield reducing, while L treatment can contribute to increasing the number of endosperm cell and grain yield.

Keyword:Summer maize; Illumination; Endosperm cell proliferation; Grain filling; Grain yield
Show Figures
Show Figures




玉米胚乳质量占籽粒质量的80%左右, 胚乳细胞的数量和充实度对粒重有决定作用^{[1, 2]}, 同时也代表着“ 库” 的高产潜力。胚乳细胞增殖速率快, 数量多, 有助于光合同化产物在籽粒中积累和淀粉粒形成, 提高籽粒充实度, 进而获得高产^{[3, 4, 5]}。玉米籽粒积累的淀粉数量决定其产量和品质^{[6, 7]}。淀粉作为光合作用的主要产物, 通过酶催化转运至胚乳细胞贮藏, 其积累速率和持续活跃时间决定粒重^{[8, 9]}, 即胚乳细胞越多, 淀粉积累量越多, 充实度越好, 粒重越高^[10]。
遮阴导致玉米籽粒胚乳细胞数和充实度降低^[10]。贾士芳等^[1]研究表明, 遮阴显著降低玉米籽粒中胚乳细胞数、淀粉及籽粒充实度, 最终降低粒重。杜成凤等^[11]和史建国等^[12]研究认为, 充足的光照有助于促进玉米光合作用, 也是玉米高产的基础; 曾希柏等^[13]研究指出, 在一定范围内植物生物量随光强的增加而提高, 玉米产量也会在一定范围随光照强度的上升而增加。
光是玉米光合作用的能量来源, 光照变化对植株光合作用、同化产物形成有极为显著的影响^[14]。开花后的光照时数、光照强度和叶面积决定了80%的玉米产量^[15]。遮阴导致夏玉米生育时期推迟, 株高、茎粗、叶面积显著减少^{[16, 17, 18, 19, 20]}, 倒伏率升高^[21], 叶片光合特性和生殖器官发育受到影响^{[22, 23, 24]}, 籽粒败育^[25], 产量下降^{[18, 19]}。1951年以来, 气候变化加剧, 日照时数减少, 太阳辐射减弱, 年平均气温不断升高, 极端天气频繁发生^{[26, 27]}, 以黄淮海区为例, 在夏玉米生长期内(6月至10月), 尤其是花粒期, 阴雨寡照天气频繁发生, 导致玉米总产量减少3%~ 6%^[15]。因此, 研究弱光胁迫对夏玉米胚乳细胞特性的影响具有重要意义。前人关于光照对夏玉米生产影响的研究多集中于营养体建成, 而关于不同时期光照对夏玉米籽粒生长发育影响的研究鲜见报道。本文通过设计不同时期遮阴和花粒期增光处理, 探讨不同光照对夏玉米胚乳细胞增殖及籽粒产量形成的影响, 为应对光照不足气候变化条件下的夏玉米高产高效生产提供理论和技术支持。
1 材料与方法1.1 试验地点山东农业大学试验农场(36.09° N, 117.09° E)具温带大陆性季风气候, 夏玉米从开花到成熟期的平均积温为1636℃ d。土壤类型为棕壤土, 播种前0~20 cm土壤养分状况为有机质9.3 g kg^-1, 全氮0.8 g kg^-1, 全磷0.9 g kg^-1, 速效磷37.2 mg kg^-1, 速效钾84.2 mg kg^-1, 碱解氮80.6 mg kg^-1。
1.2 试验设计2012— 2014年, 选用郑单958和登海605, 于6月15日播种, 种植密度67 500株 hm^-2。设计5个处理, 即对照CK: 大田自然光照; S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; L: 开花至收获期增光(L处理仅选用登海605品种)。遮光度为60%, 增光强度为1600~1800 μ mol m^-2 s^-1。利用脚手架和遮光率为60%的黑色遮阴网搭建可升降式遮阴棚, 遮阴网与玉米冠层始终保持2 m距离, 从而保证遮阴棚内小气候与大田自然光照基本一致(表1)。利用金卤灯在阴天时增光, 光照时长及强度与晴朗天气相当, 正常光照下夏玉米花粒期的日照时数平均为359.1 h, 而增光处理在该基础上大约增加光照时数206 h。小区面积为3 m× 9 m, 重复3次, 随机排列。按12 000 kg hm^-2的产量水平施用纯N 210 kg hm^-2、P₂O₅75 kg hm^-2和K₂O 150 kg hm^-2, 氮肥为尿素(含N 46%), 磷肥为过磷酸钙(含P₂O₅ 17%), 钾肥为氯化钾(含K₂O 60%)。氮肥分拔节期40%和大喇叭口期60%两次施入, 磷肥和钾肥在拔节期一次性施入, 按高产田水平进行田间管理。
1.3 测定项目与方法1.3.1 田间小气候 参照崔海岩等^[28]方法测定光照强度、气温、CO₂浓度、相对湿度、风速和地温(5 cm)。开花后连续测定7 d, 均在11:00开始测定, 计算平均值(表1)。
表1
Table 1
表1(Table 1)

表1 不同光照条件对田间小气候的影响 Table 1 Effects of different light conditions on the microclimate in the experimental field 处理 Treatment 光照强度 Light intensity (μ mol m-2 s-1) 气温 Air temperature (℃) CO2浓度 CO2 concentration (μ mol mol-1) 相对湿度 Relative humidity (%) 风速 Air flow speed (m s-1) 地温(5 cm) Soil temperature (℃) 遮阴 Shading 686.2 b 25.0 a 325.7 a 49.3 a 0.89 a 23.1 a 对照 Control 1632.7 a 25.7 a 319.3 a 48.6 a 0.93 a 24.5 a 增光 Increasing light 1618.2 a 25.8 a 318.5 a 49.2 a 0.92 a 24.4 a Values followed by a different small letter within a column are significantly different at the 0.05 probability level. 同列不同小写字母表示达到0.05显著差异

表1 不同光照条件对田间小气候的影响 Table 1 Effects of different light conditions on the microclimate in the experimental field

1.3.2 胚乳细胞 选择长势一致的植株, 于花后5、10、15、20、25、30、40、50 d各取每处理3个果穗, 剥取穗中部正常籽粒10粒, FAA固定液固定后保存于冰箱中。参照张祖建等^[29]方法测定玉米籽粒胚乳细胞数, 用Logistic方程拟合籽粒胚乳细胞增殖动态, 导出增殖特征参数。
1.3.3 籽粒灌浆特性 于吐丝期选择生长一致的植株标记, 授粉后每隔10 d取各处理3个果穗, 取中部籽粒100粒, 直至成熟, 测定籽粒体积和干重, 3次重复。用Logistic方程拟合籽粒灌浆增殖动态, 导出灌浆特征参数。
1.3.4 籽粒淀粉和粗脂肪含量 采用双波长法测定淀粉含量及组分^[30]; 采用残余油重法测定粗脂肪含量^[30]。
1.3.5 干物质积累与分配 于成熟期取样, 每个处理各5株, 每株分为茎、叶、穗轴和籽粒四部分, 烘干并称重, 用于计算干物质的积累和分配。
1.3.6 叶面积指数(LAI)与光合势(LAD) 从每个小区连续选择10株长势一致的植株, 分别在各生育时期测定每片叶的长度和最大宽度。
单叶叶面积(cm²)=叶长(cm)× 叶宽(cm)× 0.75
LAI=(单株叶面积× 每个小区的植株数)/小区面积
LAD(m²d m^-2)=(某阶段起始叶面积+该阶段结束叶面积)/2 × 间隔天数
1.3.7 叶绿体色素含量(SPAD) 于各生育时期使用SPAD-502便携式叶绿素仪(Soil-plant Analysis Development Section, Minolta Camera Co., Osaka, Japan)在每小区连续选取10株生长一致的植株测定SPAD值(开花前测定最新展开叶, VT及其以后各时期测穗位叶, 测定时避开叶脉), 取平均值。
1.3.8 测产与考种 于每小区中间3行, 随机选取30株玉米的果穗, 自然风干用于室内考种、测产。产量(kg hm^-2) = 收获穗数(ears hm^-2)× 穗粒数× 千粒重(g)× 10^-6 × (1-含水量%)/(1-14%), 收获穗数为田间调查有效穗数。
1.4 数据处理采用Microsoft Excel 2007软件处理数据, SPSS 16.0 (LSD, Duncan)软件统计分析, SigmaPlot 10.0作图。
表2
Table 2
表2(Table 2)

表2 不同光照条件对夏玉米产量及其构成因素的影响 Table 2 Effect of different light conditions on yield and yield components of summer maize 年份 Year 品种 Hybrid 处理 Treatment 产量 Yield (kg hm-2) 千粒重1000-kernel weight (g) 穗粒数 No. of kernels per ear 公顷穗数 Harvest ear number (ears hm-2) 收获指数Harvest index (%) 空秆率Barrenness (%) 2012 郑单958 Zhengdan 958 S1 3518 c 299 b 296 c 39684 c 43 c 40 a S2 6878 b 330 b 407 b 51233 b 50 b 8 b S3 1313 d 205 c 188 d 34129 d 38 d 46 a CK 10070 a 353 a 502 a 56919 a 56 a 8 b 登海605 Denghai 605 S1 2336 d 231 c 266 c 38096 c 39 d 42 a S2 7649 c 357 b 344 b 59530 b 45 c 11 b S3 1168 e 226 c 150 d 35981 d 33 e 38 a CK 11322 b 384 a 478 a 61679 b 51 b 6 bc L 12317 a 389 a 515 a 64934 a 57 a 1 c 2013 郑单958 Zhengdan 958 S1 5539 c 279 c 368 c 54077 c 37 d 16 a S2 8101 b 310 b 459 b 57040 b 50 b 9 b S3 2324 d 278 c 171 d 49633 d 44 c 19 a CK 11541 a 351 a 530 a 62117 a 58 a 4 c 登海605 Denghai 605 S1 4485 d 315 b 253 c 56300 c 40 d 16 a S2 9754 c 347 a 478 b 58892 b 46 c 8 b S3 2809 e 229 b 156 d 54829 c 33 e 16 a CK 12554 b 362 a 545 a 63593 a 51 b 4 c L 12923 a 369 a 527 a 66485 a 55 a 1 d 2014 郑单958 Zhengdan 958 S1 4797 c 250 c 355 c 54077 c 45 c 14 b S2 8094 b 277 b 478 b 61114 b 50 b 7 c S3 1518 d 203 d 165 d 45187 d 33 d 19 a CK 11819 a 334 a 555 a 63670 a 53 a 5 c 登海605 Denghai 605 S1 4361 d 290 d 282 d 53336 d 34 d 12 ab S2 9064 c 304 c 493 c 60373 c 41 c 8 b S3 1527 e 216 e 162 e 43706 e 27 e 17 a CK 10886 b 320 b 520 b 65337 b 57 b 4 c L 13605 a 363 a 578 a 70004 a 59 a 1 d ANOVA 年份Year (Y) * * NS NS * NS * * 品种Hybrid (H) * * * * NS NS NS NS 处理Treatment (T) * * * * * * * * * * * * Y× H NS NS * NS NS NS Y× T NS * NS NS NS NS H× T NS NS NS NS NS NS Y× H× T NS NS NS NS NS NS Values followed by different letters in the same column are significantly different at the 0.05 probability level. NS: not signifi cant. * : signifi cant at the 0.05 probability level; * * : signifi cant at the 0.01 probability level. S1: shading from tassel stage (VT) to maturity stage (R6; S2: shading from six-leaf stage (V6) to VT; S3: shading from emergence stage to R6; CK: natural lighting in the field; L: increasing light from VT to R6. 同列标以不同小写字母的值差异达5%显著水平。NS: 差异不显著; * 表示在0.05水平下差异显著; * * 表示在0.01水平下差异显著。S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; CK: 大田自然光照; L: 开花至收获期增光

表2 不同光照条件对夏玉米产量及其构成因素的影响 Table 2 Effect of different light conditions on yield and yield components of summer maize

2 结果与分析2.1 产量及其构成因素不同光照条件对玉米产量影响显著。郑单958品种S1、S2和S3较CK分别减产58%、26%和81%; 登海605品种S1、S2和S3较CK分别减产67%、27%和81%, L较CK增产9%。产量构成因素也发生了改变, 遮阴导致千粒重、穗粒数和公顷穗数降低, 空秆率增加, 增光后千粒重和穗粒数增加, 公顷穗数无显著变化。
表3
Table 3
表3(Table 3)

表3 不同光照条件对夏玉米成熟期干物质积累与分配的影响 Table 3 Effects of different light conditions on the dry matter accumulation and distribution at maturity of summer maize 年份 Year 品种 Hybrid 处理 Treatment 茎秆 Stalk 叶片 Leaf 籽粒 Grain 总重 Total dry matter weight (g plant-1) 干重 Dry matter weight (g plant-1) 比例 Proportion (%) 干重 Dry matter weight (g plant-1) 比例 Proportion (%) 干重 Dry matter weight (g plant-1) 比例 Proportion (%) 2012 郑单958 Zhengdan 958 S1 43.2 c 30.0 27.6 c 19.2 67.5 c 46.8 144.0 c S2 58.0 b 24.6 35.8 b 15.1 123.0 b 52.1 236.1 b S3 30.3 d 43.6 18.1 d 26.1 15.8 d 22.8 69.4 d CK 82.1 a 23.9 39.3 a 11.4 200.9 a 58.5 343.7 a 登海605 Denghai 605 S1 41.0 c 40.6 27.4 c 27.2 25.7 d 25.4 100.9 c S2 65.2 b 27.9 37.3 a 16.0 107.6 c 46.0 233.8 b S3 35.9 d 43.4 25.6 c 31.0 14.5 d 17.6 82.7 d CK 76.2 a 26.4 32.7 b 11.3 156.6 b 54.2 288.8 a L 76.0 a 24.3 30.4 b 9.7 177.4 a 56.7 312.9 a 2013 郑单958 Zhengdan 958 S1 48.7 c 28.7 35.7 ab 21.1 75.0 c 44.2 169.5 c S2 60.0 b 24.6 39.2 a 16.1 121.6 b 49.8 244.0 b S3 43.5 d 32.8 31.9 b 24.0 49.3 d 37.1 132.7 d CK 80.0 a 23.4 39.8 a 11.6 198.8 a 58.1 342.0 a 登海605 Denghai 605 S1 51.4 c 37.3 32.3 c 23.5 45.1 d 32.7 137.8 c S2 79.0 b 27.7 48.4 a 17.0 130.4 c 45.7 285.3 b S3 40.1 d 34.7 25.3 d 21.9 36.5 d 32.7 115.5 d CK 88.9 a 29.5 39.3 b 13.1 152.4 b 50.6 301.1 b L 88.7 a 26.6 38.1 b 11.4 183.6 a 55.1 332.9 a 2014 郑单958 Zhengdan 958 S1 43.9 b 31.0 29.5 b 20.8 60.8 c 42.9 141.8 c S2 78.1 a 27.5 47.2 a 16.6 140.9 b 49.7 283.6 b S3 34.4 c 32.6 24.0 c 22.7 37.3 d 35.3 105.6 d CK 80.8 a 25.2 45.8 a 14.3 171.5 a 53.4 321.0 a 登海605 Denghai 605 S1 53.3 c 34.2 32.4 b 20.8 51.3 d 32.9 156.0 c S2 65.8 b 31.3 36.7 a 17.5 86.7 c 41.3 209.9 b S3 34.3 d 39.5 21.8 c 25.1 24.6 e 28.4 86.8 d CK 78.7 a 26.4 37.6 a 12.6 168.6 b 56.6 297.7 a L 79.4 a 24.7 38.5 a 12.0 189.8 a 59.0 321.5 a Values followed by a different small letter within a column are significantly different at the 0.05 probability level. S1: shading from tassel stage (VT) to maturity stage (R6); S2: shading from six-leaf stage (V6) to VT; S3: shading from emergence stage to R6; CK: natural lighting in the field; L: increasing light from VT to R6. 同列不同小写字母表示达到0.05显著差异。S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; CK: 大田自然光照; L: 开花至收获期增光。

表3 不同光照条件对夏玉米成熟期干物质积累与分配的影响 Table 3 Effects of different light conditions on the dry matter accumulation and distribution at maturity of summer maize

2.2 干物质积累与分配遮阴后玉米成熟期干物质积累量显著下降, 郑单958品种S1、S2和S3总干物质积累量较CK分别降低55%、24%和69%; 登海605品种S1、S2和S3较CK分别降低52%、18%和65%, L总干物质积累量较CK增加9%。由各个器官的干物质积累量可知, 遮阴条件下籽粒中的积累量大幅度下降, 且均小于CK。郑单958品种S1、S2和S3籽粒干重比例分别为45%、50%和33%; 登海605品种S1、S2、S3和L所占比例分别为34%、45%、27%和57%。
表4
Table 4
表4(Table 4)

表4 不同光照条件对夏玉米籽粒胚乳细胞增殖特征参数的影响 Table 4 Effects of different light conditions on the characteristic parameters in endosperm cell proliferation of summer maize 年份 Year 品种 Hybrid 处理Treatment 系数 Coefficient ETmax (d) EWmax (× 104) EGmax (× 104 cells grain-1 d) R2 A B C 2013 郑单958 Zhengdan 958 S1 68.31 24.31 0.25 12.7 b 34.16 b 4.30 c 0.993 S2 92.03 23.61 0.27 11.7 c 46.02 a 6.24 b 0.992 S3 58.63 30.21 0.22 15.4 a 29.32 c 3.24 d 0.992 CK 93.42 27.22 0.30 10.9 d 46.71 a 7.10 a 0.996 登海605 Denghai 605 S1 64.12 31.75 0.25 13.7 b 32.06 d 4.04 d 0.994 S2 91.99 18.97 0.21 14.0 ab 46.00 c 4.83 c 0.995 S3 58.51 27.13 0.23 14.5 a 29.26 e 3.32 e 0.992 CK 101.82 27.36 0.29 11.6 c 50.91 b 7.25 b 0.996 L 105.75 28.47 0.32 10.6 d 52.88 a 8.38 a 0.996 2014 郑单958 Zhengdan 958 S1 74.06 23.96 0.25 13.0 b 37.03 c 4.53 b 0.996 S2 93.61 17.65 0.24 12.2 c 46.81 b 5.50 a 0.989 S3 68.65 12.85 0.15 16.7 a 34.33 d 2.62 c 0.992 CK 101.51 13.99 0.22 12.2 c 50.76 a 5.50 a 0.987 登海605 Denghai 605 S1 67.78 27.29 0.28 11.8 b 33.89 d 4.74 d 0.993 S2 94.55 12.09 0.22 11.6 b 47.28 c 5.07 c 0.982 S3 61.57 18.24 0.18 15.8 a 30.79 e 2.83 e 0.994 CK 103.06 13.50 0.22 11.9 b 51.53 b 5.61 b 0.985 L 111.93 14.87 0.23 11.7 b 55.97 a 6.45 a 0.985 A: ultimate growth; B: initial value parameter; C: growth-rate parameter; R2: correlation coefficient; ETmax: days to maximum proliferation rate; EWmax: weight at maximum proliferation rate; EGmax: maximum proliferation rate. S1: shading from tassel stage (VT) to maturity stage (R6); S2: shading from six-leaf stage (V6) to VT; S3: shading from emergence stage to R6; CK: natural lighting in the field; L: increasing light from VT to R6. A: 终极生长量; B: 初值参数; C: 生长速率参数; R2: 决定系数; ETmax: 达到最大增殖速率时的天数; EWmax: 最大增殖速率时的生长量; EGmax: 最大增殖速率。S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; CK: 大田自然光照; L: 开花至收获期增光。

表4 不同光照条件对夏玉米籽粒胚乳细胞增殖特征参数的影响 Table 4 Effects of different light conditions on the characteristic parameters in endosperm cell proliferation of summer maize

2.3 胚乳细胞增殖特性由图1可以看出, 各处理籽粒胚乳细胞增殖均呈“ S” 型曲线。各时期的遮阴处理胚乳细胞数目始终低于CK, 登海605 L处理籽粒胚乳细胞数目高于CK。各方程的决定系数(R²)均在0.99以上, 配合度高(表4)。遮阴导致ET_max升高, EW_max和EG_max均降低。郑单958品种S1、S2和S3的最大增殖速率较CK分别降低30%、7%和54%; 登海605品种S1、S2和S3较CK分别降低32%、23%和52%, L较CK提高15%。
图1
Fig. 1

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图1 不同光照条件对夏玉米籽粒胚乳细胞增殖的影响(标准差) ZD958: 郑单958; DH605: 登海605。S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; CK: 大田自然光照; L: 开花至收获期增光。Fig. 1 Effects of different light conditions on endosperm cell proliferation of summer maize (standard deviation) S1: shading from tassel stage (VT) to maturity stage (R6); S2: shading from six-leaf stage (V6) to VT; S3: shading from emergence stage to R6; CK: natural lighting in the field; L: increasing light from VT to R6.

2.4 胚和胚乳的干重及其比例从表5可知, 遮阴显著降低了籽粒胚和胚乳的干重, 登海605 L处理干重显著增加, 且籽粒胚和胚乳干重表现为L> CK> S2> S1> S3。遮阴后胚/胚乳比值增高, 说明遮阴对胚乳干重的影响程度大于胚。
表5
Table 5
表5(Table 5)

表5 不同光照条件对夏玉米籽粒胚、胚乳及胚/胚乳的影响 Table 5 Effects of different light conditions on embryo, endosperm and embryo/endosperm ratio of summer maize 品种 Hybrid 处理 Treatment 胚干重 Embryo weight (mg grain-1) 胚乳干重 Endosperm weight (mg grain-1) 胚/胚乳 Embryo/Endosperm (%) 郑单958 Zhengdan 958 S1 19.0 c 184.0 c 10.33 S2 19.7 b 197.3 b 9.97 S3 15.3 d 134.0 d 11.44 CK 22.0 a 235.0 a 9.36 登海605 Denghai 605 S1 18.3 d 172.7 d 10.62 S2 19.3 c 197.7 c 9.78 S3 15.7 e 137.0 e 11.44 CK 21.0 b 233.7 b 8.99 L 22.0 a 249.0 a 8.84 Values followed by a different small letter within a column are significantly different at the 0.05 probability level. S1: shading from tassel stage (VT) to maturity stage (R6); S2: shading from six-leaf stage (V6) to VT; S3: shading from emergence stage to R6; CK: natural lighting in the field; L: increasing light from VT to R6. 同列不同小写字母表示达到0.05显著差异。S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; CK: 大田自然光照; L: 开花至收获期增光。

表5 不同光照条件对夏玉米籽粒胚、胚乳及胚/胚乳的影响 Table 5 Effects of different light conditions on embryo, endosperm and embryo/endosperm ratio of summer maize

2.5 籽粒灌浆特性遮阴延缓了最大籽粒灌浆速率的出现, 其中S3影响最大, S1次之, S2最小。遮阴导致W_max和G_max下降, 登海605品种S3、S2和S1处理的W_max和G_max较CK分别下降50%、6%、8%和44%、5%、11%, 即遮阴降低了玉米籽粒最大灌浆速率及其生长量, 郑单958与登海605品种的变化趋势一致。登海605 L处理的最大灌浆速率提前出现, 提高了籽粒最大灌浆速率及其生长量。
表6
Table 6
表6(Table 6)

表6 不同光照条件对夏玉米籽粒灌浆特征参数的影响 Table 6 Effects of different light conditions on the characteristic parameters of grain-filling of summer maize 年份Year 品种 Hybrid 处理 Treatment 系数 Coefficient Tmax (d) Wmax (g 100 kernel-1) Gmax (g 100 kernel-1 d) R2 A B C 2013 郑单958 Zhengdan 958 S1 19.48 181.58 0.24 21.5 b 9.74 c 1.18 c 0.995 S2 20.70 170.45 0.24 21.4 b 10.35 b 1.24 b 0.999 S3 14.78 180.65 0.23 22.6 a 7.39 d 0.85 d 0.999 CK 24.73 94.41 0.21 21.3 b 12.37 a 1.32 a 0.996 登海605 Denghai 605 S1 24.85 90.62 0.19 23.7 a 12.43 d 1.18 d 0.998 S2 25.23 91.11 0.20 22.6 b 12.62 c 1.26 c 0.998 S3 13.50 216.29 0.22 24.4 a 6.75 e 0.74 e 0.999 CK 26.96 87.80 0.20 22.8 b 13.48 b 1.32 b 0.993 L 28.47 63.70 0.20 21.0 c 14.23 a 1.41 a 0.998 2014 郑单958 Zhengdan 958 S1 18.38 89.25 0.18 25.0 a 9.19 b 0.83 c 0.995 S2 22.96 82.96 0.19 23.3 b 11.48 a 1.09 b 0.998 S3 11.83 80.08 0.18 24.4 a 5.92 c 0.53 d 0.996 CK 23.77 97.67 0.21 21.8 c 11.89 a 1.25 a 0.995 登海605 Denghai 605 S1 19.48 68.54 0.16 26.4 b 9.74 c 0.78 d 0.997 S2 23.15 94.15 0.19 23.9 c 11.58 b 1.10 c 0.998 S3 12.80 63.71 0.14 29.7 a 6.40 d 0.45 e 0.997 CK 25.25 95.12 0.20 22.8 d 12.63 a 1.26 b 0.996 L 25.23 123.50 0.23 20.9 e 12.62 a 1.45 a 0.998 A: ultimate growth; B: initial value parameter; C: growth-rate parameter; Tmax: days to maximum grain filling; Wmax: weight at maximum grain filling rate; Gmax: maximum grain filling. S1: shading from tassel stage (VT) to maturity stage (R6); S2: shading from six-leaf stage (V6) to VT; S3: shading from emergence stage to R6; CK: natural lighting in the field; L: increasing light from VT to R6. A: 终极生长量; B: 初值参数; C: 生长速率参数; Tmax: 到达最大灌浆速率时的天数; Wmax: 灌浆速率最大时的生长量; Gmax: 最大灌浆速率。S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; CK: 大田自然光照; L: 开花至收获期增光。

表6 不同光照条件对夏玉米籽粒灌浆特征参数的影响 Table 6 Effects of different light conditions on the characteristic parameters of grain-filling of summer maize

2.6 籽粒直链淀粉、支链淀粉和粗脂肪含量从表7可知, 遮阴降低了玉米籽粒总淀粉含量, 且直链淀粉降幅更大。郑单958和登海605两品种S1、S2和S3处理的总淀粉含量较CK分别降低11%、5%、16%和10%、5%、12%, 登海605 L处理籽粒淀粉含量较CK显著增加5.9%。遮阴增加了籽粒中粗脂肪含量, 且S3增幅最大。
表7
Table 7
表7(Table 7)

表7 不同光照条件对夏玉米籽粒淀粉含量和粗脂肪含量的影响 Table 7 Effects of different light conditions on starch and gross fat content of summer maize 品种 Hybrid 处理 Treatment 直链淀粉 Amylose (%) 支链淀粉 Amylopectin (%) 总淀粉 Total starch (%) 粗脂肪 Gross fat (%) 直支比 Amylose/amylopectin rate 郑单958 Zhengdan 958 S1 14.8 c 48.7 b 63.5 c 5.6 b 29.8 c S2 20.2 b 47.5 c 67.7 b 4.9 c 43.4 b S3 10.3 d 50.0 a 60.3 d 9.1 a 19.9 d CK 25.2 a 46.3 d 71.5 a 4.7 c 56.8 a 登海605 Denghai 605 S1 11.1 d 52.2 a 63.3 d 6.3 b 20.6 d S2 17.1 c 50.1 b 67.2 c 6.1 b 33.4 c S3 9.7 e 52.2 a 61.9 d 8.0 a 17.6 e CK 19.8 b 50.7 b 70.5 b 5.4 c 39.8 b L 24.5 a 50.2 b 74.7 a 5.3 c 50.8 a Values followed by a different small letter within a column are significantly different at the 0.05probability level. S1: shading from tassel stage (VT) to maturity stage (R6); S2: shading from six-leaf stage (V6) to VT; S3: shading from emergence stage to R6; CK: natural lighting in the field; L: increasing light from VT to R6. 同列不同小写字母表示达到0.05显著差异。S1: 开花至收获期遮阴; S2: 拔节至开花期遮阴; S3: 出苗至收获期遮阴; CK: 大田自然光照; L: 开花至收获期增光

表7 不同光照条件对夏玉米籽粒淀粉含量和粗脂肪含量的影响 Table 7 Effects of different light conditions on starch and gross fat content of summer maize

2.7 籽粒产量与各生理指标的相关性分析由表8可知, W_max、G_max等籽粒灌浆参数与籽粒产量呈极显著正相关, 即W_max、G_max等越大, 籽粒产量越高, 而T_max与产量呈显著负相关。EW_max、EG_max等籽粒胚乳增殖参数与籽粒产量也呈极显著正相关, ET_max与产量呈显著负相关, 籽粒胚乳干重与产量呈显著正相关。由表9可知, LAI和LAD与籽粒产量呈显著正相关, SPAD值与籽粒产量呈极显著正相关, 即提高LAI、LAD和SPAD值有助于增加产量。
表8
Table 8
表8(Table 8)

表8 籽粒产量、籽粒灌浆特性和胚乳细胞增殖特性的相关系数 Table 8 Correlation coefficients between grain yield and characters of grain filling and endosperm cell proliferation 产量 Yield 千粒重1000-grain weight ETmax EWmax EGmax Tmax Wmax Gmax 胚乳干重 Endosperm weight 产量 Yield 1 千粒重1000-grain weight 0.932* 1 ETmax -0.886* -0.982* * 1 EWmax 0.994* * 0.924* -0.860 1 EGmax 0.963* * 0.950* -0.950* 0.939* 1 Tmax -0.905* -0.913* 0.873* -0.913* -0.926* 1 Wmax 0.810* 0.965* * -0.972* * 0.798* 0.860 -0.811* 1 Gmax 0.862* 0.986* * -0.979* * 0.855 0.896* -0.862* 0.994* * 1 胚乳干重Endosperm weight 0.983* * 0.969* * -0.953* 0.966* 0.992* * -0.916* 0.883* 0.919* 1 * * : correlation is significant at the 0.01 probability level (2-tailed); * : correlation is significant at the 0.05 probability level (2-tailed). ETmax: days to maximum proliferation rate; EWmax: weight at maximum proliferation rate; EGmax: maximum proliferation rate; Tmax: days to maximum grain filling; Wmax: weight at maximum grain filling rate; Gmax: maximum grain filling. * * 表示在1%水平下显著相关; * 表示在5%水平下显著相关。ETmax: 达到最大增殖速率时的天数; EWmax: 最大增殖速率时的生长量; EGmax: 最大增殖速率; Tmax: 到达最大灌浆速率时的天数; Wmax: 灌浆速率最大时的生长量; Gmax: 最大灌浆速率。

表8 籽粒产量、籽粒灌浆特性和胚乳细胞增殖特性的相关系数 Table 8 Correlation coefficients between grain yield and characters of grain filling and endosperm cell proliferation

表9
Table 9
表9(Table 9)

表9 籽粒产量和LAI、LAD、SPAD值的相关性系数 Table 9 Correlation coefficients of grain yield, LAI, LAD, and SPAD 产量 Yield 叶面积指数 LAI 光合势 LAD 叶绿体色素含量SPAD 产量 Yield 1 叶面积指数 LAI 0.770* 1 光合势 LAD 0.786* 0.817* 1 叶绿体色素含量SPAD 0.835* * 0.861* * 0.885* * 1 * * : Correlation is significant at the 0.01 probability level (2-tailed); * : correlation is significant at the 0.05 probability level (2-tailed). * * 表示在0.01水平下显著相关; * 表示在0.05水平下显著相关。

表9 籽粒产量和LAI、LAD、SPAD值的相关性系数 Table 9 Correlation coefficients of grain yield, LAI, LAD, and SPAD

3 讨论3.1 不同光照对夏玉米产量和干物质积累量的影响光合作用决定了玉米90%以上的干物质, 且干物质的积累、分配与产量显著正相关^{[31, 32, 33]}, 尤其是生育后期的干物质积累分配特性决定了夏玉米的最终产量^[34]。前人研究表明, 光照不足, 尤其是生育后期光照不足严重制约玉米生产, 表现为叶片光合性能下降, 籽粒灌浆强度降低, 干物质向籽粒中的转运量下降, 直接影响夏玉米产量^{[35, 36]}。Cui等^[31]研究指出, 雌穗小花分化对光照非常敏感, 光照不足降低小花分化总数, 降低穗粒数, 导致产量降低。本试验结果进一步表明, 花前遮阴降低了光合产物积累量, 花后遮阴降低了后期干物质积累量和籽粒灌浆速率, 导致产量降低, 即花前遮阴削弱了“ 源” 的生产能力, 花后遮阴影响了“ 库” 的充实。各处理玉米产量和干物质积累量降低幅度为S3> S1> S2, 说明夏玉米花粒期对光照更为敏感, 花粒期充足的光照更有利于夏玉米高产^{[37, 38, 39]}。
3.2 不同光照对夏玉米胚乳细胞增殖的影响胚乳细胞数目代表了籽粒“ 库” 的潜力, 也代表该潜力的实现程度, 而单个胚乳细胞的充实状态也对产量的提高具有重要作用^[7]。胚乳细胞越多, 积累的淀粉粒越多, 充实度越高, 粒重越高^[2]。本研究表明, 在授粉后30 d左右, 籽粒胚乳细胞数基本达到最高值(图1), 胚乳细胞停止或减少分裂, 胚乳细胞构建基本完成, 以淀粉积累为主, 籽粒生长进入淀粉粒的充实阶段, 淀粉含量和粒重快速增加。遮阴后玉米籽粒胚乳细胞增殖的最大速率下降, 导致胚乳细胞数目降低(降低幅度为S3> S1> S2), 最终表现为籽粒发育进程延缓, 淀粉积累量下降, 籽粒库容量变小, 充实度下降, 粒重降低, 相反, 增光条件下胚乳细胞增殖速度快、数目增多(表8), 籽粒积累同化产物的速度加快, 容纳较多的淀粉粒^[8], 提高产量。
3.3 不同光照对夏玉米籽粒灌浆的影响胚乳细胞形成后, 籽粒生长进入有效灌浆期, 即籽粒淀粉粒的充实扩大期, 完成淀粉的积累和单粒质量的增加。胚乳细胞数目代表着“ 库” 的潜力, 增库则需要提高灌浆速率, 提前最大灌浆速率出现的日期, 保证光合产物高效地运转到籽粒^[40]。本研究表明, 遮阴降低了籽粒灌浆速率, 推迟了灌浆速率最大值的出现日期, 导致灌浆活跃期缩短, 严重影响籽粒的正常灌浆, 相反, 增光则有利于提高籽粒的灌浆效率。
增光处理一方面有利于玉米积累更多的光合产物, 提高干物质量^[39], 达到增“ 源” 的效果, 茎、叶等临时性贮藏器官向籽粒输送的光合产物增加, 籽粒灌浆速率和生长量增加, 籽粒干重所占比例升高; 另一方面增殖速率和最大生长量显著升高, 胚乳细胞能够较快地达到最大增殖速率, 胚乳细胞数目增多, 淀粉含量显著提高, 即扩大了籽粒的“ 库” 容量, 胚乳细胞有较高的充实度, 籽粒灌浆速率提高, 粒重增加。相反, 光照不足导致玉米光合速率下降, 光合产物向籽粒中的转运量降低^[37]。遮阴下胚乳细胞发育异常, 表现为增殖速率降低、最大增殖速率延迟出现以及最大生长量降低, 籽粒中的胚乳细胞数目严重下降, 淀粉含量、籽粒充实度、籽粒灌浆速率降低, 且开花后遮阴处理影响最大, 其粒重和产量降低幅度分别达20%和60%左右。

4 结论花粒期光照显著影响夏玉米籽粒的生长发育。遮阴降低玉米籽粒胚乳细胞数目、淀粉含量和细胞充实度, 导致减产, 增光促进粒重增加, 提高产量。因此, 在实际生产中通过适当调整播期, 避开阴雨寡照天气, 合理布局种植密度, 改善田间光照条件有助于提高胚乳细胞的增殖速率及灌浆速率, 保证光合产物高效向籽粒运转, 实现高产。
The authors have declared that no competing interests exist.

作者已声明无竞争性利益关系。


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