全 文 ：第 16 卷 第 1 期
Vol. 16 No . 1
草 地 学 报
ACTA AGRESTIA SINICA
2008 年 1 月
Jan. 2008
# 博士论文摘要#
温度胁迫对苜蓿和柱花草光合作用及 N还原的影响
博士生 :莫亿伟 导师:郭振飞
(华南农业大学生命科学学院, 草业生物技术实验室, 广东 广州 510642)
苜 蓿 ( Medicago sativa L. ) 和 柱 花 草
( S ty losanthes guianensi s ( A ubl. ) Sw. )均为优质
豆科牧草,前者耐寒但不耐热, 主要种植在北方地
区,而后者耐热不耐寒, 主要种植在热带亚热带地
区。为探讨这两种牧草对温度胁迫的适应机制, 本
文从温度胁迫对其伤害、渗透调节物质含量的变化、
光合作用、N还原等方面开展了研究。
本研究所用苜蓿品种为/陇东苜蓿0, 柱花草品
种为/ CIA NT 1840。种子播种6~ 7周后,选取生长
良好的幼苗为试验材料, 放入人工气候箱分别进行
低温( 5~ 6 e )、高温( 35~ 36 e )处理,据其特性苜蓿
低温处理 5 d、高温处理 2 d后取样测定; 柱花草低
温处理2 d、高温处理5 d后取样测定。以在 25 e 条
件下生长的植株为常温对照。研究结果如下:
1 温度胁迫对苜蓿和柱花草叶片糖代谢的影响
与常温( 25 e )对照相比, 高温处理 2 d 后苜蓿
叶片相对含水量降低,相对电导率和丙二醛( MDA)
含量显著增加, 表明苜蓿受到高温伤害;但柱花草叶
片在高温处理 5 d后仍维持较高的相对含水量、较
低的相对电导率和 MDA 含量, 表明其受高温伤害
较轻。低温 5 d处理后苜蓿叶片保持较高的相对含
水量、较低的相对电导率和 MDA含量,表明其受低
温伤害较少;但低温处理 2 d 后柱花草叶片相对含
水量下降、相对电导率和 MDA 含量显著增加,表明
其受低温伤害严重。
苜蓿和柱花草的可溶性总糖和蔗糖含量、蔗糖
磷酸合酶( SPS)和蔗糖合酶( SS)活性在高温和低温
处理后均有增加,但低温处理的增加量更大, 说明低
温对糖积累影响更大。温度胁迫降低苜蓿和柱花草
叶片淀粉含量, 常温下它们的淀粉含量最高, 高温次
之,低温最少。
2 温度胁迫对苜蓿和柱花草叶绿素荧光参数和光
合速率的影响
高温胁迫使苜蓿叶片光合速率降低最大,低温
胁迫次之;低温胁迫使柱花叶片光合速率降低最大,
高温胁迫次之。高温处理后苜蓿叶绿素荧光参数
Fv / Fm , –PSÒ和 qp 急剧降低,而低温处理后 Fv / Fm,
–PSÒ , qp下降较少;高温对柱花草叶绿素荧光参数影
响不大,低温处理后柱花草 Fv/ Fm , –PSÒ, qp 急剧降
低。结果说明高温胁迫下苜蓿光系统Ò活性降低较
大,而低温胁迫下柱花草光系统Ò活性降低幅度更大。
高温胁迫明显降低苜蓿叶绿体 AT P 合酶活
性、降低叶片 AT P 含量叶绿体 AT P 含量, 但是苜
蓿受低温影响较小; 低温胁迫明显降低柱花草叶片
AT P 含量,但高温胁迫对柱花草叶片 AT P 含量影
响不大。苜蓿叶片 RuBP 羧化酶( RuBPcase)和果
糖 1, 6-二磷酸酯酶( FBPase)活性在高温下降幅最
大,低温胁迫次之; 柱花草叶片 RuBPcase 和 FBP-
case活性在低温下降幅最大,高温胁迫次之。
3 温度胁迫对苜蓿和柱花草 N同化的影响
高温下苜蓿叶片硝酸还原酶( NR)、亚硝酸还原
酶( NiR)、谷氨酰胺合成酶( GS)和谷氨酸合成酶
( GOGA T)都显著下降, 但高温对柱花草的这些酶
影响较小。低温下苜蓿叶片 NR、NiR、GS 和
GOGAT 活性降低不大, 但柱花草的这些酶活性都
显著降低。两种牧草叶片的硝态氮和铵态氮在高温
胁迫下含量最高, 低温下次之,常温最低。温度胁迫
降低了 NR和 GS的活性, 导致硝态氮和铵态氮在
叶片内积累。
本研究证明苜蓿耐低温,对热敏感,而柱花草耐
热但对低温敏感。温度胁迫下 PS Ò受到伤害, 影响
了光合磷酸化的正常进行, 使叶绿体和叶片内 ATP
供应不足,这可能是柱花草叶片在低温下或苜蓿在
高温下光合速率及 N同化能力降低所致。
关键词:苜蓿; 柱花草; 硝酸还原酶; 光合作用; AT P 合酶; 蔗糖合酶
中图分类号: Q945 文献标识码: A 文章编号: 1007-0435( 2008) 01-0100-03
完成日期: 2007年 1月
收稿日期: 2007-11-30; 修回日期: 2007-12-12
作者简介:莫亿伟( 1971- ) ,男,广西人,博士研究生
导师简介: 郭振飞( 1964-) ,男,研究员,研究方向为草业生物技术, E-mail: zhfguo@ scau. edu . cn
第 1期 莫亿伟等: 温度胁迫对苜蓿和柱花草光合作用及 N还原的影响
The Effects of Temperature Stress on Photosynthesis and Nitrogen
Reduction of Alfalfa and Guyana Stylosanthes
Candidate: MO Y-i w ei Supervisor: GU O Zhen-fei
( Biotechn ology Laboratory of T urfg ras s and Forages, C ol lege of Life S cience, South Chin a Agricul tu ral U nivers ity,
Guangzhou, Guan gdon g Province 510642, China)
Alfalfa ( Medicago sativa L. ) and Guyana sty losanthes ( S ty losanthes guianensis ( Aubl. ) Sw. ) are
tw o important for ag e legumes w ith high feeding quality. A lfalfa is cold- tolerant , but heat- sensitive, while
Guyana sty losanthes is heat- tolerant , but cold-sensit ive. In order to explor e the adaptat ion mechanisms to
temperature str ess, the physio logical responses of sugars metabolism , pho to synthesis, and nit ro gen r educ-
t ion o f these tw o forag e legumes under low and high temperature st resses w er e comparat ively studied by
this paper .
The seedlings of alfalfa ( M. sat iv a cv. Longdong ) and Guyana sty losanthes ( S. guianensi s cv.
CIANT 184) w er e grow n in g lasshouse w ith temperature 20 to 30 e under natural light condit ion. Six to
seven-w eek seedlings of these tw o legumes w ere div ided into three groups and transferr ed to gr ow th cham-
bers w ith three temper ature t reatments, respect ively. T he f irst g roup w as subjected to temper ature at 5 to
6 e as cold t reatment , the second g roup at 35 to 36 e as heat t reatment , and the third g roup at 25 e as
control. Af ter a given time o f t reatment , the physiolog ical indices w ere measured and the experimental re-
sults w ere summarized in the follow ing sect ions.
1 Sugars metabolism in response to temperature stress
Compared to seedling s under room temperatur e, signif icant decrease o f relativ e w ater content and in-
crease of MDA content and ion leakage in alfalfa leaves occurred af ter 2 days o f heat st ress, w hile no signif-
icant changes w ere detected for those under co ld st ress fo r 5 days. T he results indicate that alfalfa w as eas-
ily injur ed by heat st ress but tolerant to cold st ress. On the contrary, Guyana stylosanthes maintained re-l
at ively high relative w ater content , low ion leakage, and low MDA content af ter 5 days of heat st ress,
w hile the MDA content and ion leakage w ere signif icant ly increased under cold st ress, indicat ing that Guy-
ana sty losanthes w as to ler ant to heat str ess, but sensit ive to co ld st ress.
The contents o f total so luble sugars and sucro se and the act ivities o f sucrose phosphate synthase
( SPS) and sucrose synthase ( SS) w er e enhanced in bo th legumes af ter co ld or heat st ress t reatments in
comparison to control, but more enhancements w er e detected under cold st ress than heat st ress. Cold
st ress had a more inf luence on sugars accumulat ion than heat str ess. Starch contents decr eased in both leg-
umes after cold or heat st ress w ith highest content under control and low est under cold str ess.
2 Chlorophyll fluorescence parameters and photosynthetic rates in response to temperature stress
Photosynthetic rates in both legume forages decreased after heat or co ld stress, but the responses w ere
dif ferent betw een the tw o legumes. T he photosynthetic rate of alfalfa decreased more under heat st ress
than cold st ress, w hile it decreased more under cold st ress than heat st ress in Guyana sty losanthes. The
chlorophyll f luor escence par ameters ( Fv / Fm , –PSÒ and qP ) in alfalfa decreased g reat ly after heat st ress,
but decreased slight ly under cold st ress. In contrast, these parameter s decreased greatly under cold st ress
and w ere no t affected under heat st ress in Guyana sty losanthes. The results indicate that pho tosy stem Ò
act ivity in alfalfa w as more sensit ive to heat st ress than Guyana sty losanthes, w hile that in Guyana
stylo santhes w as more sensit ive to cold st ress than alfalfa.
ATP synthase activ ity and ATP content in chlor oplasts of alfalfa w er e greatly decreased under heat
st ress, w hile those w ere lit t le af fected under cold st ress. AT P content w as also decreased in Guyana
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草 地 学 报 第 16卷
stylo santhes under cold st ress, but it w as not af fected under heat st ress. RuBPcase and FBPase act ivit ies
in both legumes decr eased under both heat and cold str ess w ith low er activit ies in alfalfa and higher act iv-i
t ies in Guyana sty losanthes under heat str ess than cold st ress, respectively.
3 N assimilation in response to temperature stress
Act ivit ies of nit rate r eductase ( N R) , nit rite reductase ( NiR) , g lutamine synthase ( GS) , and gluta-
mate synthetase ( GOGA T) w er e great ly decr eased in leaves o f alfalfa under heat st ress, w hile they w ere
litt le af fected under co ld st ress. On the contrary, they w ere gr eat ly decreased in Guyana sty losanthes un-
der cold st ress but lit t le af fected under heat st ress. T emperature st resses induced the accumulat ion of
NO-3-N and NH +4-N in leaves o f both legumes, and higher levels w ere accumulated under heat str ess in
comparison to cold st ress. T he decreased activ it ies o f NR and NiR caused by temperatur e st resses resulted
in the accumulat ion o f NO3--N and NH4+-N in leaves.
In summary, alfalfa exhibited tolerant to co ld st ress but sensit ive to heat str ess, w hile Guyana
stylo santhes w as tolerant to heat but sensit iv e to cold str ess. T emperature str esses resulted in the injury of
photosyntem Ò and therefo re inhibited pho tophosphory lation, w hich led to the lim its of AT P supply in
leaves, decreased photosynthesis, and N assim ilat ion.
Key words: Alfalfa; Guyana stylosanthes; Nit rate reductase; Pho to synthesis, AT P synthase; Sucro se
synthase
(责任编辑 才 杰)
(上接 93页)
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