ISWC OpenIR  > 水保所知识产出(1956---)
大气二氧化碳浓度升高对玉米幼苗 碳氮资源分配的影响
宗毓铮
Subtype博士
Thesis Advisor上官周平
2013-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Keyword高浓度 Co 2 光合作用 碳氮分配 水分胁迫 氮胁迫 玉米
Abstract

大气 CO 2 浓度不断升高是全球气候变化的主要组成部分,其对个体植株生
理生态过程的调节直接影响到群落组成与大气-植物-土壤圈的物质循环。在降
雨量小、蒸发量大且土壤贫瘠的黄土高原,作物生长遭受着土壤干旱-复水(有
限降雨)-干旱的循环过程,干旱与氮素缺乏是作物生长的主要限制因素。目前
关于 CO 2 浓度升高对 C 3 植物生理过程的影响与调控的工作较多,而 C 4 植物对
CO 2 浓度升高的生理生态适应性仍存在不少争论。光合调节是植株适应气候变
化最直接的表现方式,体内碳氮分配与转运策略是评估植株长期适应能力的主
要内容。研究 CO 2 浓度升高、干旱与氮素胁迫三者的交互作用对 C 4 植物光合
能力与体内碳氮分配与转运策略的影响有利于为探索旱区植物对未来气候变化
的适应性提供理论依据。
本研究以水培玉米幼苗为试验材料,采用人工气候室内控制 CO 2 浓度,聚
乙二醇(PEG-6000)模拟水分胁迫的方法,利用碳氮化学计量技术、同位素示
踪技术、叶绿素荧光和气体交换测定技术,从玉米生长、光合生理、碳氮分配
及转运、碳氮利用等角度,研究了水分胁迫下高浓度 CO 2 减轻叶片光合抑制的
作用机制、源库器官活力对植株生长的影响,分析了高浓度 CO 2 提高源库器官
活力的途径,探讨了氮胁迫抑制高浓度 CO 2 作用的机理,以及受旱植株对不同
程度复水的生理适应能力。主要研究结果如下:
(1) CO 2 倍增显著减少了受旱玉米叶片有活性的 PSII 反应中心数目,提
高了单位反应中心光能捕获、转化与传递能力,进而增强叶片单位横截面积的
能量流动效率及电子传递速率;在碳反应过程中,CO 2 倍增使受旱植株具有较
高饱和光合速率,表明 CO 2 倍增可以通过提高光能利用为碳反应提高较多还原
力。
(2)在正常供氮条件下,CO 2 倍增可通过增强玉米叶片 PEPC 的羧化能力
(V pmax )并减轻气孔限制(SL)缓解由水分胁迫产生的光合限制;在氮素限制
条件下,CO 2 倍增可通过提高玉米叶片 Rubisco 羧化能力(V max )并减轻气孔限
制,部分地减缓光合限制。CO 2 倍增下氮素限制使植株向叶片分配较多氮素,提高光合氮利用效率并降低整株氮利用效率。CO 2 倍增可以减轻干旱对叶片光
合作用的抑制,但随着植物氮素供应水平不同,其受抑程度也存在一定差异。
(3)CO 2 倍增加快了受旱植株源叶碳输出速度、老叶碳输出量、以及库叶
碳输入量,并减少了碳素从地下部向地上部的反向运输。CO 2 倍增延长了新固
定氮素在根系中的存留时间,增加了库叶氮素的总输入量。CO 2 倍增改变了体
内碳氮分配与再利用方式,使库叶碳氮素供应显著增加,并增强了植株生物量
与碳氮素积累,表明 CO 2 倍增有助于减轻植株受水分胁迫的影响。
(4)CO 2 浓度升高显著提高了玉米整株氮素积累量与库叶氮积累量。停止
氮素供应后,高浓度 CO 2 下水分胁迫处理通过减缓玉米功能叶“新氮”输入速度,
加快库叶“新氮”输入速度,并减少库叶“老氮”输入量以维持受旱植株生长,对
老叶氮素的输出没有显著提高。
(5)受旱玉米复水后,CO 2 倍增较正常 CO 2 使玉米植株具有较低的含水量
与较高的生长速率,并具有较高的光合能力(F v /F m , Φ PSII , P n , P n  /T r and P n  /G s )与
新叶生长潜力,即使在低氮条件下也是如此,说明 CO 2 倍增通过较高的光合能
力与较低含水量使植株提高水分利用效率、增强生物量积累。
关键词:高浓度 CO 2 ;光合作用;碳氮分配;水分胁迫;氮胁迫;玉米

Other Abstract

Rises in ambient CO 2 are expected to cause global climate changes, including
increases in air temperature and shifts of regional scale rainfall patterns, which lead
to decreased soil water availability in some areas of the world. Elevated CO 2 affect
plant physiological and ecosystem processes and probably lead to the suppression of
plant N availability that limits the effect of CO 2 fertilization. Previous study have
shown that C 3 plants under elevated CO 2 often maintain growth during short term
drought due to improved water use efficiency, however, reduce long-term adaption
and result in down-regulation of photosynthesis. The maintenance of rapid growth
under conditions of CO 2 enrichment is directly related to the capacity of
photosynthesis and carbon and nitrogen transport in plants and its contribution to the
new foliar formation. Less is known about the phorosynthesis and carbon and
nitrogen transport in C 4 plants in response to drought, N limitation, precipitation
frequency and increasing CO 2 .
To test the effects of water and nitrogen limitation on plants under elevated CO 2 ,
maize (Zea mays), the world's most important C 4 crop, was planted to experience
combined elevated CO 2 (380 or 750 µmolmol -1
stomatal
, climate chamber), water stress (15%
PEG-6000) and nitrogen limitation (N deficiency treated since the 144th drought
hour) and rewatered at three intensities (300mL, 600mL, 900mL of distilled water).
During the growing period, the performance of PSII and electron transport, 
limitation, non-stomatal limitation, photosynthetic potential parameters, leaf
nitrogen use efficiency, patterns of carbon and nitrogen delivery, and new leaf
productivities of the maize plants were investigated using chlorophyll-a fluorescence
OJIP induction curves, A/C i curves and 13 C and  15
(1). Compared to water-stressed maize under atmospheric CO 2 , the elevated  CO 2 treatment interacted with water stress decreased number of active reaction
centers but increased antenna size and energy flux (absorb photon flux, trapping flux
and electron transport flux) of per reaction center in PSII. So the electron transport
rate (J) was increased, despite of the indistinctively changed quantum yield for
electron transport and energy dissipation. In carbon reaction, the combination of
elevated CO 2 and water stress treatment had the robust saturated photosynthetic rate
(A sat ). This study demonstrates that maize at doubled CO 2 was capable of
transporting more electron flow into carbon reaction.
(2). Elevated CO 2  could alleviate drought-induced photosynthetic limitation
through increasing capacity of PEPC carboxylation (V pmax ) and decreasing stomatal
limitations (SL). The N deficiency exacerbated drought-induced photosynthesis
limitations in ambient CO 2 . Elevated CO 2  partially alleviated the limitation induced
by drought and N deficiency through improving the capacity of Rubisco
carboxylation (V max ) and decreasing SL. Plants with N deficiency transported more
N to their leaves at elevated CO 2 , leading to a high photosynthetic nitrogen-use
efficiency but low whole-plant nitrogen-use efficiency. The stress mitigation by
elevated CO 2 under N deficiency conditions was not enough to improving plant N
use efficiency and biomass accumulation. The study demonstrated that elevated CO 2
could alleviate drought-induced photosynthesis limitation, but the alleviation varied
with N supplies.
(3). Compared to water-stressed maize under atmospheric CO 2 , the treatment
combining elevated CO 2 with water stress increased the accumulation of biomass
and partitioned more carbon and nitrogen to the formation of new leaves. Maize
seedlings enhanced the carbon resource in aging leaves and the carbon pool in new
leaves but decreased the carbon counterflow capability of roots. The seedlings also
had increased residence times of new nitrogen in roots and then delivered more
nitrogen to new leaves. Thus maize supported the development of new leaves at
elevated levels of CO 2 by altering the transport and remobilization of carbon and
nitrogen. In drought presence condition, increased activity of new leaves to store
carbon and nitrogen sustains enhanced growth under elevated CO 2 in maize.
(4). Elevated CO 2 significently increased the accumulation of nitrogen in
whole plant and new leaves. With nitrogen starvation, elevated CO 2 retard the new
nitrogen transport in functional leaves, accelerate the new nitrogen transport in ne  leaves to sustains growth under drought.
(5). After they were rewatered, pre-drought stressed and N limited plants with
ambient CO 2 increased their water content higher than that of elevated CO 2 , while
the enhancement of growth rate were negatively proportional to the increasing plant
water content. Elevated CO 2 could help rewatered seedlings to have higher
photosynthetic capacity (F v /F m , Φ PSII , P n , P n  /T r and P n  /G s ) and new leaf recovery
ability under low water content, no matter the seedlings suffered nitrogen deficiency
or not. The study demonstrated that elevated CO 2 could help drought stressed
seedlings to have higher carbon assimilation rates under low water uptakes, as a
result to improve leaf water use efficiency, which allows the plants to have much
better performance under drought following being re-watered.
KEY WORDS: Elevated CO 2 ;Photosynthesis;N and C Allocation;Water Stress;
N Stress;Maize

Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8962
Collection水保所知识产出(1956---)
Recommended Citation
GB/T 7714
宗毓铮. 大气二氧化碳浓度升高对玉米幼苗 碳氮资源分配的影响[D]. 北京. 中国科学院研究生院,2013.
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