水分虧缺對小麥灌漿中后期穗部光合特性和14C-同化物轉(zhuǎn)運的影響

米慧聰謝雙澤李 躍丁 寒呂金印,*

1西北農(nóng)林科技大學生命科學學院, 陜西楊凌 712100;2西北農(nóng)林科技大學理學院, 陜西楊凌 712100

水分虧缺對小麥灌漿中后期穗部光合特性和14C-同化物轉(zhuǎn)運的影響

米慧聰1謝雙澤2李 躍1丁 寒2呂金印1,*

1西北農(nóng)林科技大學生命科學學院, 陜西楊凌 712100;2西北農(nóng)林科技大學理學院, 陜西楊凌 712100

為探討水分虧缺對小麥灌漿中后期穗部同化物轉(zhuǎn)運的影響, 利用14CO2同位素示蹤技術(shù), 對于2個抗旱性不同小麥品種的盆栽試驗, 測定中度水分虧缺下小麥穗部光合特性及灌漿中后期碳同化物的轉(zhuǎn)運。結(jié)果表明, 花后20 d, 中度水分虧缺下水地品種鄭引1號旗葉和穗部凈光合速率(Pn)分別下降50.2%和19.9%, 旱地品種普冰143分別下降33.7%和12.8%, 后者顯著小于前者。14CO2示蹤試驗表明, 花后15～20 d籽粒中14C-同化物快速積累, 花后25 d達到最高值; 灌漿中后期(花后15～20 d)穗部苞片中14C-同化物向外快速轉(zhuǎn)運, 灌漿末期(25 d)碳同化物已徹底轉(zhuǎn)移。成熟期, 中度水分虧缺下小麥籽粒中14C-同化物積累高于正常供水處理, 且旱地品種普冰143積累量高于水地品種鄭引1號。中度水分虧缺下, 鄭引1號產(chǎn)量下降36.7%, 高于普冰143的23.2%。適度水分虧缺對旱地品種穗部凈光合影響較小, 并促進了灌漿中后期穗部苞片中碳同化物的向外轉(zhuǎn)運, 可能是維持旱作小麥穩(wěn)產(chǎn)的生理基礎(chǔ)。

小麥; 水分虧缺; 碳同化物轉(zhuǎn)運;14C-標記

干旱是限制我國小麥北方主產(chǎn)區(qū)小麥產(chǎn)量的主要非生物脅迫因素之一[1]。水分虧缺導致葉片光合能力快速下降, 影響碳同化物轉(zhuǎn)運, 降低小麥產(chǎn)量[2]。已有研究表明,小麥穗部苞片、穗下節(jié)、葉鞘、莖等非葉器官對水分脅迫不敏感, 是干旱條件下籽粒灌漿期間碳同化物的重要來源[3-4]。穗部具有重新固定籽粒呼吸釋放的 CO2、接受外界光照和 CO2等明顯生理優(yōu)勢[5-7], 即使在干旱條件下仍能保持相對穩(wěn)定的光合能力[3,8-9]。

Gebbing和 Schnyder[5]通過減源試驗, 提出面包小麥穗部光合作用對籽粒的貢獻可達 22%～45%; Sanchez-Bragado等[10]利用13C標記方法, 研究發(fā)現(xiàn)小麥地方品種穗部對籽粒的貢獻高于現(xiàn)代品種。適度干旱可以顯著促進花后莖鞘中14C同化物的運轉(zhuǎn)[11]。干旱條件下穗部光合對籽粒灌漿的貢獻增加[12-14], 適度干旱脅迫促進了小麥花前和灌漿前期穗部同化物向籽粒的轉(zhuǎn)運[15-16]。Jia等[17]對水分虧缺下不同小麥品種灌漿速率進行Logistic方程擬合表明, 花后15 d灌漿速率達到高峰?；ê?8 d小麥植株開始衰老, 籽粒經(jīng)灌漿脫水在花后24 d生理成熟[3]。灌漿中后期相對于旗葉穗部器官具有衰老延遲性[3], 但水分虧缺下不同抗旱性小麥灌漿中后期穗部光合及碳同化物的轉(zhuǎn)運規(guī)律還不十分清楚。

本試驗研究水分虧缺下不同抗旱性小麥穗部光合特性及灌漿中后期碳同化物的分配率, 探討穗苞片灌漿中后期光合及籽粒的調(diào)運差異, 為揭示旱作小麥的穩(wěn)產(chǎn)高產(chǎn)機制提供依據(jù)。

1 材料與方法

1.1 試驗設(shè)計

選用不同抗旱性冬小麥(Triticum aestivum L.)品種,其中普冰143由西北農(nóng)林科技大學培育, 2004年9月經(jīng)過陜西省審定, 為耐旱品種, 并適合旱地種植; 鄭引 1號原產(chǎn)意大利, 由河南省農(nóng)業(yè)科學院于 20世紀 80年代引進,為水地品種。

2014年10月至2015年6月在西北農(nóng)林科技大學北校區(qū)遮雨網(wǎng)室進行盆栽土培試驗。供試土壤為關(guān)中平原農(nóng)田耕作層(0～22 cm)風干紅油土, 土壤最大田間持水量時凈含水量為29.2%。2014年10月18日播種, 設(shè)正常供水和中度水分虧缺兩種處理, 土壤含水量分別為最大田間持水量的70%～75%和45%～50%。抽穗期開始控水, 每天按標準稱重法補水, 每處理重復25盆。

1.2 測定項目和方法

1.2.1 旗葉和穗部凈光合速率(Pn) 采用便攜式光合儀(LI-6400 XT, LI-COR,USA)在花后10、15、20、25 d晴天9:00—11:00測定旗葉和穗部凈光合速率。采用光合儀測定旗葉光合速率, 配置的 LED紅藍光源, 光強為 1000 μmol m-2s-1, 大氣CO2濃度390 μmol mol-1, 每處理重復4次。采用特制的圓柱形葉室與便攜式光合儀(LI-6400 XT, LI-COR, USA)配套測量穗部, 依據(jù)當時自然光變化配合使用人工紅藍光源, 使測定時光照強度為1000 μmol m-2s-1[15], 根據(jù)Teare和Peterson[18]和裘昭峰等[19]的方法計算穗表面積, 分別測穗穎片及芒的表面積, 穗面積 = 穗長 × 穗寬 × 3.8; 芒面積＝頂3小穗的芒長×直徑×結(jié)實小穗數(shù)×π。

1.2.214CO2標記測定同化物轉(zhuǎn)運分配 在灌漿中后期(花后15 d)選擇長勢及花期一致的小麥, 于上午9:00用聚乙烯塑料袋套住穗部, 用注射器注入5 mL14CO2, 標記強度為81.77×104Bq L-1, 立即封口。光合1 h后用NaOH溶液回收殘留于袋中的14CO2, 去除塑料袋。

于花后15、20、25、30 d, 每次采樣4株, 將旗葉、穎片、外稃、芒、籽粒等器官分開, 在105℃殺青, 70℃烘箱烘干至恒重磨碎, 稱取50 mg, 加0.5 mL 60% HClO4和0.7 mL 30% H2O2。80℃消化4 h, 加10 mL閃爍液, 暗處過夜, 測定總放射性活度。以上操作均重復3次。用多功能液體閃爍計數(shù)系統(tǒng)(LS-6500, Beckman, USA, 計數(shù)效率≥95%), 測定14C cpm值, 通過計數(shù)效率校正, 將cpm值校正為dpm值。

1.2.3 農(nóng)藝性狀指標及水分利用效率(WUE) 小麥成熟后, 分別統(tǒng)計小穗數(shù)、可育小穗粒數(shù)、穗粒數(shù)、穗粒重、千粒重, 統(tǒng)計籽粒產(chǎn)量, 計算收獲指數(shù)。WUE=每盆籽粒產(chǎn)量(g) /每盆總耗水量(kg)。

1.3 數(shù)據(jù)處理與分析

用Microsoft Excel 2013及SPSS 20.0軟件統(tǒng)計分析數(shù)據(jù), 用Duncan’s檢驗差異顯著性。

2 結(jié)果與分析

2.1 中度水分虧缺對不同抗旱性小麥灌漿中后期旗葉和穗部Pn的影響

在灌漿中后期2個供試小麥品種旗葉Pn快速下降(圖1-A)。與對照相比, 中度水分虧缺處理下2個品種旗葉Pn下降顯著(P＜0.05), 尤其灌漿后期(花后 20 d), 水地品種鄭引1號下降50.2%, 旱地品種普冰143下降33.7%, 前者下降幅度明顯大于后者。

2個品種灌漿中后期穗部 Pn呈緩慢下降趨勢(圖1-B)。與正常供水相比, 花后20 d, 鄭引1號穗部Pn下降19.9%, 大于普冰143的12.8% (P＜0.05)。中度水分虧缺處理下穗部凈光合速率下降幅度顯著小于旗葉, 與旗葉相比, 穗部保持相對較高的凈光合速率, 表現(xiàn)出一定的光合優(yōu)勢, 且鄭引1號穗部光合速率受水分虧缺影響大于普冰143。

2.2 中度水分虧缺對小麥灌漿中后期穗部14C-同化物轉(zhuǎn)運及分配的影響

14CO2示蹤試驗表明, 籽粒中14C-同化物花后15～20 d快速積累, 花后25 d (標記后10 d)達到最高值(圖2-A), 中度水分虧缺下旱地品種普冰143籽粒中14C-同化物分配率為91.1%, 而水地品種鄭引1號為86.5%。與正常供水相比, 花后30 d (收獲期)中度水分虧缺下普冰143籽粒14C-同化物分配率增加1.9%, 而鄭引1號增加1.7%。

中度水分虧缺促進了灌漿中后期(花后15～20 d )穗部苞片中14C-同化物向外轉(zhuǎn)運。與正常供水相比, 花后30 d (收獲期)水分虧缺下普冰143和鄭引1號穎殼14C-同化物分配率降幅分別為1.3%和0.2% (圖2-B)?；ê?0 d, 中度水分虧缺下普冰143和鄭引1號外稃中14C-同化物分配率分別為 1.6%和 2.0%, 而正常供水處理分別為 2.0%和3.3% (圖2-C), 中度水分虧缺下水地品種外稃中14C-同化物的滯留明顯高于旱地品種。而花后30 d (收獲期), 中度水分虧缺下普冰143和鄭引1號芒中14C-同化物分配率分別為 3.9%和 5.4%, 略高于正常供水處理的 3.7%和 4.2% (圖 2-D), 可能與灌漿期芒的早衰有關(guān)。收獲時中度水分虧缺下水地品種芒中14C-同化物分配率明顯高于旱地品種, 表現(xiàn)出少量的滯留現(xiàn)象。尤其指出的是, 花后 15 d,芒中14C-同化物分配率(12.2%～13.9%)明顯高于穎殼(7.6%～11.4%)和外稃(7.9%～1.4%)中(圖 2-B, C, D), 灌漿中后期旗葉中有少量14C-同化物(0.5%～1.4%) (圖2-E)。中度水分虧缺促進了穗部苞片(穎殼、外稃、芒)碳同化物向外轉(zhuǎn)運, 且旱地品種穗部14C-同化物的滯留小于水地品種。

圖1 中度水分虧缺對小麥灌漿中后期旗葉(A)和穗部(B)凈光合速率的影響Fig. 1 Effect of water deficit on net photosynthetic rate (Pn) of flag leaf (A) and spike (B) after anthesis in wheatCK: 正常供水; MD: 中度水分虧缺。數(shù)據(jù)為3次生物學重復的平均值±標準差, 誤差線上不同字母表示相同生育期處理間有顯著差異(P ＜ 0.05)CK: normal water supply; MD: moderate water deficit. Data are means ± standard deviations of three biological repeats. Different letters above the error bars indicate significant difference among treatments on the same sampling day (P ＜ 0.05).

圖2 中度水分虧缺對灌漿中后期小麥籽粒(A)、穎殼(B)、外稃(C)、芒(D)和旗葉(E)中14C-同化物分配率的影響Fig. 2 Effect of water deficit on the distribution of14C-assimilates accumulated in grain (A), glume (B), lemma (C), awn (D), and rachis (E) of wheat after anthesisCK: 正常供水; MD: 中度水分虧缺。數(shù)據(jù)為3次生物學重復的平均值±標準差。CK: normal water supply; MD: moderate water deficit. Data are means ± standard deviations of three biological repeats.

2.3 水分虧缺對小麥產(chǎn)量性狀和WUE的影響

中度水分虧缺下旱地品種普冰 143穗粒重和千粒重降低的幅度分別為30.1%和10.0%, 而水地品種鄭引1號分別為39.6%和16.2% (表1), 前者降幅顯著小于后者。中度水分虧缺下, 普冰142和鄭引1號產(chǎn)量下降顯著(P＜0.05)。普冰 143收獲指數(shù)降幅為2.9%, 小于鄭引 1號的15.5%。中度水分虧缺下, 兩品種的 WUE變化顯著(P＜0.05), 普冰143升高10.3%, 而鄭引1號則下降11.1% (表2)。表明中度土壤干旱對旱地小麥產(chǎn)量和收獲指數(shù)的影響小于水地品種。

表1 干旱處理對不同抗旱性品種產(chǎn)量相關(guān)性狀的影響Table 1 Yield of different wheat varieties under different treatments

表2 水分虧缺對不同抗旱性品種產(chǎn)量、生物量、收獲指數(shù)和水分利用效率的影響Table 2 Effects of water deficit on yield, biomass, harvest index and water use efficiency (WUE) in different drought-resistant varieties

3 討論

小麥穗部光合作用對籽粒產(chǎn)量具有重要貢獻[9,20]。而干旱等不利條件加速了葉片的衰老進程[15], 降低了旗葉光合產(chǎn)物對籽粒的貢獻率。近年研究表明, 逆境下小麥穗部表現(xiàn)出更強的干旱適應能力[21], 而葉片對干旱脅迫更為敏感[22]。本研究中, 中度水分虧缺下兩種不同抗旱性小麥灌漿中后期穗部凈光合速率緩慢下降, 而旗葉凈光合速率呈快速下降趨勢。且水分虧缺下水地品種鄭引1號穗部、旗葉凈光合速率降幅均大于旱地品種普冰143。Jia等[17]認為, 水分虧缺條件下穗部比旗葉具有光合優(yōu)勢。本研究也有類似結(jié)果, 適度干旱對穗部光合影響小于對旗葉的影響, 逆境下穗部表現(xiàn)出光合持久性。

干旱誘導了小麥早衰[23-24], 縮短了生育期, 增加了莖鞘等臨時庫14C-同化物的轉(zhuǎn)運[13,24-25], 并且穗部對籽粒的貢獻增大[26]。Evans等[27]報道, 干旱下小麥穗部光合碳同化物對籽粒產(chǎn)量的貢獻率增幅為34%～43%, 且水分脅迫下小麥穗部光合對籽粒貢獻率高于正常供水處理[11]。本研究發(fā)現(xiàn), 中度水分虧缺促進了灌漿中后期小麥穗部碳同化物向籽粒的轉(zhuǎn)運(圖2-A), 旱地品種籽粒調(diào)用量相對較高; 同時, 中度水分虧缺促進了旱地品種小麥穗部苞片(穎殼、外稃)的14C-同化物向外轉(zhuǎn)運(圖2-B, C), 減少了滯留。本研究還佐證了Bidinger等[26]穗部碳同化物的再轉(zhuǎn)運對籽粒灌漿至關(guān)重要的結(jié)論。Abebe等[28]認為芒是穗部主要的光合器官, 大麥中芒對穗部光合貢獻可達 90%[29]。本研究中芒14C-同化物分配率明顯高于穎殼和外稃(圖 2-D)。Olugbemi[30]用14C同位素標記試驗, 證實芒中約有 99%的光合同化產(chǎn)物轉(zhuǎn)運至著生該芒的小穗中。因此, 穗部器官中芒的光合固碳作用不容忽視。另外, 2個品種旗葉中存在少量來自穗部的14C-同化物(圖2-E), 可能是干旱使旗葉早衰的情況下, 穗部調(diào)運碳同化物以維持其代謝活動。中度水分虧缺下, 旱地品種產(chǎn)量下降幅度小于水地品種, 可能是由于旱地品種灌漿中后期穗部苞片碳同化物滯留少, 更多的光合產(chǎn)物運輸?shù)阶蚜Ｖ小１狙芯拷Y(jié)果表明, 中度水分虧缺加速了小麥葉片衰老, 降低了灌漿期旗葉光合能力,而穗部器官光合能力可維持在相對較高水平, 且對旱地品種影響較小; 適度干旱處理促進了旱地品種籽粒對穗部苞片碳同化物的調(diào)運, 增加了籽粒干物質(zhì)的積累。這可能是旱地品種相對高產(chǎn)的原因之一, 充分挖掘小麥穗部等非葉器官光合固碳潛力, 可為實現(xiàn)小麥高產(chǎn)提供重要途徑。

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Photosynthetic Characteristics and14C-Assimilate Translocation in Wheat Spike during Mid- to Late-filling Stage under Water Deficit

MI Hui-Cong1, XIE Shuang-Ze2, LI Yue1, DING Han2, and LYU Jin-Yin1,*

1College of Life Sciences, Northwest A&F University, Yangling 712100, China;2College of Science, Northwest A&F University, Yangling 712100, China

The objective of this study was to understand the effect of water deficit on photosynthetic and assimilate translocation in wheat spike during mid- to late-filling stage by using two pot-cultured14C-labelled varieties differing in drought tolerance. Under moderate water deficit, the net photosynthetic rate (Pn) of flag leaf and spike at 20 days after anthesis (DAA) decreased by 50.2% and 19.9% in Zhengyin 1 (drought sensitive) and by 33.7% and 12.8% in Pubing 143 (drought tolerance), respectively. Obviously, the decrease of photosynthetic capacity in the drought-sensitive variety was greater than that in the drought-resistant variety in response to water stress. The14C-assimilates accumulated rapidly in grains during 15-20 DAA and reached the peak at 25 DAA. Simultaneously, the14C-assimilates in glume, lemma, and awn had a quick outward transportation during 15-20 DAA, and completely transferred to grains at 25 DAA. Compared with normal water condition, moderate water deficit resulted in significantly higher14C-assimilates in grains at maturity. The14C-assimilate accumulation in Pubing 143 was significantly higher than that in Zhengyin 1, and the yield loss caused by drought stress was 23.2% in Pubing 143 and 36.7% in Zhengyin 1. Compared with drought-sensitive variety, drought-tolerant variety received less influence of moderate water deficit on spike Pnand stronger assimilate translocation from spike bracts to grain. This might be the physiological basis of stable yield in drought-resistant wheat variety.

Wheat; Water deficit; Assimilates translocation;14C-labelling

10.3724/SP.J.1006.2017.00149

本研究由國家自然科學基金項目(31271624)資助。

This study was supported by the National Natural Science Foundation of China (31271624).

*通訊作者(Corresponding author): 呂金印, E-mail: jinyinlu@163.com, Tel: 13572196187

聯(lián)系方式: E-mail: mihuicong@163.com, Tel: 18220827092

稿日期): 2016-04-08; Accepted(接受日期): 2016-09-18; Published online(

日期): 2016-11-07.

URL: http://www.cnki.net/kcms/detail/11.1809.S.20161107.1407.002.html