劉 梅， 鄭青松， 劉兆普， 郭世偉

(南京農(nóng)業(yè)大學(xué)資源與環(huán)境科學(xué)學(xué)院， 江蘇省海洋生物學(xué)重點(diǎn)實(shí)驗(yàn)室， 江蘇南京 210095)

鹽脅迫下氮素形態(tài)對(duì)油菜和水稻幼苗離子運(yùn)輸和分布的影響

劉 梅， 鄭青松， 劉兆普， 郭世偉*

(南京農(nóng)業(yè)大學(xué)資源與環(huán)境科學(xué)學(xué)院， 江蘇省海洋生物學(xué)重點(diǎn)實(shí)驗(yàn)室， 江蘇南京 210095)

油菜； 水稻； 氮素形態(tài)； 鹽脅迫； 離子運(yùn)輸； 離子積累

土壤中鹽分過(guò)多會(huì)影響作物生長(zhǎng)，并導(dǎo)致產(chǎn)量下降。鹽脅迫對(duì)植物的傷害作用主要是通過(guò)滲透脅迫、離子毒害、營(yíng)養(yǎng)失衡三個(gè)方面來(lái)實(shí)現(xiàn)的[1]。鹽脅迫引起的滲透脅迫對(duì)干物質(zhì)分配、細(xì)胞伸展、葉片光合作用等造成不利影響，抑制植物生長(zhǎng)[2]。植物在鹽漬條件下生長(zhǎng)會(huì)吸收大量的Na+，形成離子毒害，對(duì)植物代謝造成傷害[3-4]。植物具有避免鹽離子積累的機(jī)制，如將Na+儲(chǔ)存在液泡或排入質(zhì)外體[5]，Na+從細(xì)胞質(zhì)排到細(xì)胞外和液泡能降低鹽離子對(duì)細(xì)胞的毒害作用[6]，控制Na+的積累是植物耐鹽的重要生理過(guò)程[7]。

研究表明，只有水稻、蘆葦?shù)壬贁?shù)植物能夠在銨態(tài)氮作為單一氮源條件下生長(zhǎng)良好，大多數(shù)旱地植物的氮營(yíng)養(yǎng)以硝態(tài)氮為主[20]。因此，了解不同形態(tài)氮素營(yíng)養(yǎng)對(duì)作物在鹽脅迫下的響應(yīng)顯得尤為重要[21]。油菜是典型的喜硝植物，水稻是典型的喜銨植物。本文通過(guò)對(duì)油菜和水稻幼苗供應(yīng)不同形態(tài)氮素培養(yǎng)后進(jìn)行鹽脅迫處理，比較鹽脅迫對(duì)不同形態(tài)氮素營(yíng)養(yǎng)下油菜和水稻幼苗生長(zhǎng)、Na+和K+在不同組織中的積累和運(yùn)輸?shù)挠绊懀U述不同形態(tài)氮素營(yíng)養(yǎng)對(duì)兩種作物耐鹽機(jī)制的影響。

1 材料與方法

1.1 供試材料

油菜品種： 南鹽油1號(hào)(甘藍(lán)型油菜)；水稻品種： 汕優(yōu)63(雜交秈稻)。

1.2 試驗(yàn)設(shè)計(jì)與處理

試驗(yàn)在南京農(nóng)業(yè)大學(xué)牌樓溫室實(shí)驗(yàn)基地進(jìn)行，白天室內(nèi)溫度為28_35℃，光合有效輻射為1000_1500 [μmol/(m2·s)]左右，光照時(shí)間每天10小時(shí)左右。

1.3 植株生物量的測(cè)定

樣品分地上部(油菜包括莖、葉片和葉柄；水稻包括莖和葉)和根系兩部分采集，先用自來(lái)水沖洗，再用去離子水清洗干凈，用吸水紙吸干表面水分后，于105℃烘箱中殺青30 min后，降溫至70_80℃烘至恒重，測(cè)定干重。

1.4 植株Na+和K+含量的測(cè)定

取0.05 g植株組織干樣，經(jīng)H2SO4-H2O2消煮，取過(guò)濾后的待測(cè)液5 mL置于50 mL容量瓶，用去離子水定容。待測(cè)樣品用火焰光度計(jì)(FP6410，上海)測(cè)定[24]。

1.5 植株Na+積累量的測(cè)定

植物根系(地上部)Na+積累量=根系(地上部)Na+濃度×根系(地上部)干重。

Na+傷害度(單位Na+積累量對(duì)植株根系(地上部)生物量的影響)=[對(duì)照植株根系(地上部)生物量-鹽處理植株根系(地上部)生物量)]/[(鹽處理植株根系(地上部)Na+積累量-對(duì)照植株根系(地上部)Na+積累量]

1.6 木質(zhì)部傷流液的收集及Na+和K+濃度的測(cè)定

收獲前一天進(jìn)行植株木質(zhì)部傷流液的收集。稱取0.1_0.2 g脫脂棉，在距根基2 cm處用手術(shù)刀片切斷莖稈，10 min后用潔凈的濾紙吸走斷莖處的組織液，以防韌皮部汁液的交叉污染，然后迅速將脫脂棉包在莖稈并使莖端面與其接觸，用保鮮膜包好，收集1 2小時(shí)(晚18： 00至次日早6： 00)[25]。用注射器將脫脂棉中汁液擠出后過(guò)濾置于試管中，待測(cè)樣品用火焰光度計(jì)(FP6410，上海)測(cè)定。

1.7 韌皮部汁液的收集及Na+和K+濃度的測(cè)定

收獲前一天進(jìn)行植株韌皮部汁液的收集。在距根基2 cm處用手術(shù)刀片切斷莖稈，將地上部浸泡在裝有30 mL的20 mmol/L LiOH-EDTA溶液的玻璃瓶(玻璃瓶空瓶稱重)中(用LiOH避免測(cè)定時(shí)陽(yáng)離子相互干擾)。每個(gè)容器和植物材料放置在密封容器中，黑暗中放置12 h(晚18： 00至次日早6： 00)獲得滲出物[26]。滲出液過(guò)濾后用火焰光度計(jì)(FP6410，上海)測(cè)定。

1.8 數(shù)據(jù)處理

采用SPSS軟件進(jìn)行相關(guān)分析和單因素方差(ANOVA)分析，用LSD多重檢驗(yàn)法對(duì)不同處理結(jié)果進(jìn)行顯著性檢驗(yàn)。

2 結(jié)果與分析

2.1 不同氮素形態(tài)及鹽脅迫對(duì)油菜和水稻生物量的影響

注(Note): 同列中不同字母表示差異顯著(P<0.05) Different letters in the same column indicate significant difference (P<0.05).

2.2 不同形態(tài)氮素營(yíng)養(yǎng)及鹽脅迫對(duì)油菜和水稻組織Na+和K+含量的影響

鹽脅迫條件下，硝營(yíng)養(yǎng)水稻莖和葉Na+含量顯著高于銨營(yíng)養(yǎng)水稻，根系Na+含量顯著低于銨營(yíng)養(yǎng)(水稻營(yíng)養(yǎng)液添加0.1 mmol/L Na2SiO3保證Si營(yíng)養(yǎng)供應(yīng)[27])。對(duì)照及鹽脅迫條件下，硝態(tài)氮營(yíng)養(yǎng)水稻根系K+含量高于銨營(yíng)養(yǎng)；鹽脅迫下，硝態(tài)氮營(yíng)養(yǎng)水稻莖K+含量明顯下降，銨態(tài)氮營(yíng)養(yǎng)水稻幼苗不受影響；氮素形態(tài)及鹽脅迫對(duì)水稻葉片K+含量無(wú)顯著影響。

注(Note): 同列中不同字母表示差異顯著(P<0.05) Different letters in the same column indicate significant difference (P<0.05); “nd”—小于檢測(cè)限No detected.

2.3 不同形態(tài)氮素營(yíng)養(yǎng)及鹽脅迫對(duì)油菜和水稻Na+傷害度的影響

注(Note): 同列中不同字母表示差異顯著(P<0.05) Different letters in the same column indicate significant difference (P<0.05).

2.4 不同形態(tài)氮素營(yíng)養(yǎng)及鹽脅迫對(duì)油菜和水稻木質(zhì)部及韌皮部汁液Na+和K+濃度的影響

注(Note): 同列中不同字母表示差異顯著(P<0.05) Different letters in the same column indicate significant difference (P<0.05).

3 討論與結(jié)論

3.1 硝態(tài)氮處理植株比銨態(tài)氮處理植株更耐鹽

3.2 不同形態(tài)氮素營(yíng)養(yǎng)在鹽脅迫條件下對(duì)油菜和水稻Na+和K+運(yùn)輸及積累的影響

我們采用單位Na+傷害度表示植株對(duì)Na+的敏感程度，盡管硝營(yíng)養(yǎng)油菜和水稻根系及地上部Na+積累量高于銨營(yíng)養(yǎng)(表4)，但是生物量減少幅度小于銨營(yíng)養(yǎng)植株(圖1)。因此，銨營(yíng)養(yǎng)油菜和水稻對(duì)Na+更敏感；油菜根系生長(zhǎng)受Na+影響大于地上部，水稻則是地上部生長(zhǎng)受抑制更顯著(圖1)。本研究中，油菜NaCl處理含量高達(dá)150 mM NaCl，屬于重度脅迫，根系直接與營(yíng)養(yǎng)液接觸，因此受到的Na+毒害也更直接。對(duì)于水稻而言，研究表明，50_100 mM NaCl處理不同耐鹽性水稻均顯示水稻幼苗地上部對(duì)鹽害的反應(yīng)比根系更敏感[23]。鹽脅迫條件下，兩種供氮形態(tài)油菜和水稻表現(xiàn)出不同的傷害部位，可能與其自身生長(zhǎng)模式、調(diào)節(jié)機(jī)制等有關(guān)，具體原因有待進(jìn)一步研究。

綜上所述，硝營(yíng)養(yǎng)油菜和水稻木質(zhì)部-韌皮部對(duì)離子的調(diào)控能力更強(qiáng)， Na+傷害度更小，因此供應(yīng)硝態(tài)氮植株比銨態(tài)氮更耐鹽。

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Effects of nitrogen forms on transport and accumulation of ions in canola (B.napusL.) and rice (OryzasativaL.) under saline stress

LIU Mei, ZHENG Qing-song, LIU Zhao-pu, GUO Shi-wei*

(CollegeofResourcesandEnvironmentalSciences,NanjingAgriculturalUniversity/JiangsuProvincialKeyLaboratoryofMarineBiologyNanjing210095,China)

canola; rice; nitrogen form; salt stress; ions transport; ions accumulation

2014-03-07 接受日期： 2014-04-15

國(guó)家支撐項(xiàng)目(2011BAD13B09)資助。

劉梅(1989—)，女，重慶人，碩士研究生，主要從事植物逆境營(yíng)養(yǎng)生理生態(tài)研究。E-mail： 2011103003@njau.edu.cn * 通信作者 E-mail： sguo@njau.edu.cn

S143.1+9; S565.4

A

1008-505X(2015)01-0181-09