全 文 ：广 西 植 物 Guihaia 2O(1)：52—58 2000年 2月
文 章 编号 ：IO00—3142(2000 3 01—005g一07
A prel im inary study on the diurnal variation of
net photosynthetic rate and transpiration
rate for Chimonanthus praecox
LI Jing，LIU Ying—di，CHENG Gong—xi，CHEN Jun，ZHU Jie-ying
t Imtilutbm F~,dogy，．， Univcrsily．Hunan 416000．China )
Abstract：The measu renlent of the net phott~ynthetlc rate (Pn)and transplratlon rate (Tr)for Ch／-
Ⅲ Hf^ f~aeto (L )Link．under the natural conditions on sunny and cloudy days was carried out．
The influences of envlronmentaI factors on d urnaI variation of Pn and Tr for C praeco,r w盯e aI∞ an．
alyzed inthis paper．The present experimental results show：(1)Thediurnal courts ofthe PnforC．
prae~r on sunny and cloudy days were both double—ridged curves．On sunny days the two peak values
0f Pn appeared earlier and the general Pn value wa higher than that on cloudy days．Th phenomenon
of midday depres~ion of photosynth wⅫ obviously oh~rved on sunny days． (2)The diurnal cotlt-m~
of Tr for ．prae~ on sunny days was of n single-ridged-form．1．}Ie peak value of Tr reached beyond
10 ntmo LH20 nl under the condition of intenFce light and high temperature in the afvemoon．On
cloudy days，the Tr CUTVe smooth．The transpiration was weak-below 0．8 mmol H2O m-I dur_
ins a whole day．(3)The Pn of the wild C．praecox reached as high as 23．6．umo[CO2 m’ 一 when the
photosynthedc active radiation(PAR)was 800~ 900．umolm ．a temperature (Ta)28℃ ，relative
humidity (Rh)75％ ．Thelight saturation point andlight compensation point ofC．praecox werl~qui忱
low，about 900 fmlolm 一 and 2O izmolm-2s—re~pectlvely．(4)PAR and Ta we dominant eoh#~*l
factors limiting the diurnal variation of Pn and Tr for e． praecox．This plant was．~ensitive to high
temperatu re and intense light．W hen PAR exceed ed the light saturation point and Ta surpa．s,．~ l 42℃ ，
the transpiration increased rapidly while the energy transformation and water use efficiency (W UE)
decreased remarkablyt the photosynthetic capacity was much weakened。al1 these above read to the
sharp de~end of Pn．
Key words：( ^ ， praecox~net photosynthetic rate~transpiration rate
1 Introduction
Chimonanthus pFaFLO．T (1．) I,ink．，one of the famous traditional flowers and economic
plants in China，is of high research and exploitation value(Jiang＆ Li 1979，Zhao et a1．1993)．
The studies on its resource distribution，formation，chemical composition analysis，classification
and cultivation have received great attention(Chen& Yang 1992，Wu＆ Hu 1995，Zhao el,a1．
Author resume：Mr 【1i jing(195 5一)．Assistant Prclessor．deals with the study 0f phnt phy．tot~ y
SupPorted by Science Foundatim~of Education Committee of Hunan Pra is e．
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l期 李 菁等 ：蜡梅光合与蒸腾速率 日变化的初步研究 53
1993，Zhan ，Huang＆ l iu1993)．We alsomade some studies onthe species varieties and basic
characlcristics of wild C．praec．JT(Chert，IA＆．1．i et a1．1997，Li，Chen＆ Li et a1．，1997)．No
experimental paper on ecophysiological characteristics of C． praecox (especially the wild ones)
has been rcporled so far．The net photosynthetic rate(Pn)and transpiration rate(Tr)for C．
proeco．r both on sunny and cloudy days were measured，and a preliminary analysis on the re—
sponses of these physiological process to environment was also presented in this paper，aiming at
understanding its ecophysiological characteristics and providing scientific basis for more effective
protection and rat ionaI utilization of this peculiar plant in China．
2 M aterials and methods
The sample plants for testing were selected in the wild Chimonanthus praecox (1 ．) IAnk．
forest in Aizhai vilage，Jishou city，Hunan province(for further information about the habitat
sec Iilerature l ，Chen et“1． 1 997)．The CI一30l PS (CID Ine． USA)was used to m eas lie the
Pn．Tr．photosynthetic active radiation (PAR)，air temperature (1~a)，leaf temperature (T1)，
air relalivc humidity (Rha)，chamber relative humidity (Rhc)，CO2 content(Cc)of the living
functional leaves on Ihe 2～ 3 years old plants．The 1ear samples were tested once an hour fronl7：
00 to 18：00 on typical sunny and cloudy days and repeated 3～ 5 times in each measurement．The
average Val Ltes were calculated from eaveraI stable data．
Threc typical 1)lants and 3～ 5 leafs of each plant were selected in the measurement．The di—
urnal c0urse measurement results were an average of two day of measurement in both sunny蚰 d
cloudy day．
The gauze layers were gradually added to reduce the hght radiated on leaf chamber，thus to
control the PAR intensity on the leaf samples．By this way，the Ught reapcDse of C．praecaz was
measured and a light response curve was drawn Out according to it．
3 Results and analysis
3．1 fhe diurnaI variatlons of the natural environm ental factors
The diurnal course of PAR was of a single—ridged —form on sunly days(Fig．1)．The PAR
gradually increased from 7：00，the peak value of 2 260#molm。 s。。appeared at 13：O0，thaaPAR
desccnded to the lowest value of 150,umolm‘ s- at 18：00．On cloudy days，the PAR di~nat
course was smooth and~howed no such wide fluctuation as on sunuy days，the PAR dc~a quite
low during the whole day with the highest value 157．9#molto a。。and the lowest value 43．5
g．molm。 s～
The diurnal variation of Ta was simihr to that of PAR (Fig．2)．On sunny days，the Ta
rose with the radiation increase from 8：O0 tiIl reaching the peak value of 41．9 C at 13：00,then
Ta deercased gradually．The Tt was always higher than Ta．The highest TI value of 49．5 ℃ ap-
pearcd at 13：O0 while the leaf was in midday depression of photosynthesis(at that time Pn wes
at the bottom in the Pn curve)．On cloudy days，Ta and T1 kept tow and
．
fluctuated only in the
range of 20～ 26 C
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e 7 B 9 1O 11 12 t 3 1 4 1 5 t 6 17 1 8 19
t／h
Fig 1 [)htrn．I va riation of photosynthedc
Lct1ve tadI“__on (PAR)．PAR—s，
sunny；PAR—c．doudy．
6 7 8 9 10 11 12 1 3 I4 5 16 17 I8 19
t／h
Fig 2 Diurnal variation of tempe rature．Ta-s
is air temperature (Ta)，and TI—s．]ear
temperature(TD in sonny day}Ta-c
is Ta，and Tl-c，T1 in cloudy day
The Rh had quite different diurnal courses on sunny and cloudy days(Fig．3)．The air rela—
tire humidity(Rha)had a wide fluctuation with the h Eghest Rha of 74．8 at 7：00 and the low—
est Rha of 27 at l3～ l 4：00 on sunny dayswhereas on cloudy daystherewas only a small vari—
ation range between 76．8 (at 8：oo)and 67 (at 16～ 17：oo)．In tbe tWO different weathers，
the Rhc was higher than Rha c0rrespondingly．The diurnal variation of Rha and Rhe approxi—
mated same，that ，te Rhc had wider fluctuation on sunny days(76．5 ～43．6 )than on
cloudy days(81．5 ～ 73．1 )．
On both sunny and cloudy days，the air CO2 content(Co)decreased gradualy from the
morningtothe afternoon，yet at18：0O，itincreased alittle(Fig．4)．Thefluctuationwga small，
about 415～ 324 ppm。andtheCc values on sunny and cloudy dayswere roughlythe samethough
t was a lhtle bigher 01 cloudy days．
6 7 8 9 1O 11 12 13 14 15 16 17 18 19
，／h
Fig．3 Diurnal varii*tion of RH．Rha—s； RH of ai r．
and Rhc— ．RH in chnm[>er in sunny day；Rha-c is RH
0f⋯ ．Find Rhe-c．RH in chamber in cloudy day．
3．2 The dinrnRI variations of Pn and Tr
4513
E 4O0
士
宅3513
300
250
6 7 8 9 1O11 121314151617 1819
，／h
Fig．4 Diurnal variation of CO2 Content
Cc—s is CO2 Content in sunny day；
Cc-c，CO2 Content in cloudy day．
On sunny days，the diurnal course of Pn for C．praeco2r was a double—ridged curve (Fig．5)．
The first peak value of 21．7 I~mo[CO2 nl s’。，which was the highest Pn during a whole day．ap一
∞ ∞ ∞ ∞ 们 。
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1期 李 菁等：蜡梅光台与蒸腾速率 日变化的初步研究 55
F．eared at 8：00．Al 1 6：【】(j the second peak value of 16．2 gmol C02 m s。‘appeared． During the
time of midday depression of photosynthesis at about 1 3：00，the photosynthesis of the leaf was
the weakest and the Pn dropped to the bottom of 3．6／zmo[CO2 m s～，a decrease of 8O in con—
trast 10 the first Pn peak value．so the phenomelmn of midday depression of photosynthesis was
quite distinct．On cloudy days，the diurnal course of Pn for C．praecox was approximately a dou—
hie—ridged Curve wflh the first and second peak values appeared at 11：00 and 17：00，about 14．8
and 1 1 5 tmm l( (]!m’ s～respectively． The two peak values on cloudy days appeared later than
on sunuy days．No nmrked decline appeared between the two peak 4alues，which indieated that
on cloudy days．C． ，‘f n had no midday depression of photosynthesis．
25
20
§1 5
’。
5
0
B 7 8 9 t0 11 12 13 14 15 16 t7 1 B 19
f／n
Fig 5 D{ttrna[、。c Lr L-i_l0n of net photosynthetic rate
L【]C ^ tⅢ ， “ preGtvL~(L．)1．ink．
Pn— ，net photosynthesis in sunny day，
Pn—c．net phot0 ynthe 1s in c|oudy day．
6 7 8 9 1011 121314 15 16 17’8 19
t／h
Fig．6 Diurnal variation of transpiration rate
in Chimo~tf,ghus praecox (L_)Link．
Tr— ，transpiration rate in sunny day，
Tr-s．transpiration rate in cloudy day．
The diurnal entlrse of Tr for C．praeco．r on sunny days W；EK~a single—ridged curve(Fig．6)．
It showed a stable increase from the lowest value of 1．4 mmol H2O m。 s。 at 7：00 to the peak val-
ue of l0．3 mmol H 2O nl‘ s at about 14：00，then Tr decreased grt~duaDy．On cloudy days，the
Tr kept low ，varying at the range of 0．2～ 0．8 mmol H2O m。 s—during a whole day，yet at 16：
00～ 1 7：O0，it reached 1．0～ 1．1 mmol H2O m-gs～．The diurnal eour,ae of Tr for C． 4删 f on
cloudy days was snmoth on the who re．
3．3 The I ight response eur~e
t—th mca n
i ： ～
surement of light re—
sponse for C． praecow
was carried out in suit—
able environment with
W atle a ! ! !竺!! !兰 ! 兰! !型里竺 竺型竺 1
7：0l_8：00 9：00 l0；0 ll：0 l2 J 0 13；0 l4；0 15；0 l6 0 l7 J0 18；0
aily
训^蚺I■e
Ta about 30 C ，Rh 75 ～ 80 ．A light response curve was made according to the experimental
data (Fig．7)．The total average standards error was within a range of 1 3 ．The nght compe n—
sation iJolnt and light saturation point of this plant were measured to be about 2O~tmolm。s’ and
900 tmm]m respectively．exhibiting the photosynthetic characteristics of shade plant on this
佗 仲 8 6 4 2 O
一一sz．Eq 工l。EE】J_
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56 广 西 植 物 2O卷
aspect·
3．4 W ater ilge efficiency of Chimonam hus
praecox
W ater use efficiency (W UE)refers to the
volume of C() assimilation per unit of transpir—
ing sun]of water，being tile ratio of Pn／Tr
(Bierhuizen Sialyer 1 965)． The following
table is an evaluation of W UE for C． pt~1PC0r
on sunny and cloudy days (Tab． 1)，which
shows clearly that ori cloudy days， the W UE
was m ueb higher， Ibe average value during a
whole day is four times for that on sunny days．
During a day． W U E nr C． praeco．r in the
morning is distinctly higber tban in the after—
O 200 400 6OO 800 1O00
PA molto- s。1】
Fig 7 Light response for net photosynthetic
ratein ChlmoneaLtht~ praeco．r (L．)Link．
noon，which implies that this plant can use water more effectively，
．
transit energy more eeortomi·
eally and maintain high photosynthesis and growth on cloudy days and in the morging of sunny
days．Knowing tbal is of directive significance on making suitable habitats for cultivation and im·
proving the administration level of the C．praeco．r garden．
4 Discussion
4．1 The photosynthetic capacity and light response
The photosyn~hetie capacity of a plant refers to the highest Pn gained by the plant with eer-
rain vitality in normal and suitable environment(T archer 1980)．In the present experiment，the
Pn reached as high as 21．7～ 23．6~-tmol COim一 s- (this index was gained from the light rosportse
measurement)．In fact．the Pn 0r C．praec~r was possible to reach higher on conditions of using
a com pletely Aped Hew lear and in tile optimum state of all the environmental factors．Even
tbough，compared with the Pn of several other kinds of plant(Tab．2)，the value of 23．6 Was
quite high，which,；bowed a rather strmlg photosynthetic capacity of the wild C．praeL,oJc．
As to tlle
light response of
C． pt ，J ， no
spa ciaI expert—
pa_elt has been
condueted so
far．The present
pretmlm ary re—
Table 2 Comparisons 0n the photosynthetic capacity of Chimmtanthus n f and
gever~d other kinds of pla~t(Guo，Zhang& Li el at： 御 ，G岫，Shen 8L Wu
． I 996，Chen& Zhang 1 994，Liu．Li& Shi 1999．Xu，Yang& Xu 1998)
suits of ibis lest to the wild C．[raecoae showed that its light saturation point and light compensa—
tion point were low ，this plant has som e typical characteristics of shade plant on this aspect．One
thing shoutd be pointed OUt here：the light responac c,f the leaf samples vaned with the variation
of climate，habitats and cultivation stage．Zhao Tianpang declared that the youn．~of cultivated
∞ 柚 侣 佃 O
f ．E～0ul0E三c
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l期 李 菁等 ：蜡梅光合 与蒸腾 速率 日变 化的初 步研究 57
C． ／3,~-or-c rLT had stronger shade—tolerance whereas the adult had an inclination for the sunlight
(ZhaoTianpang，1 993)． Therefore，further and systematic researches on the light response of
wild C ／3,~-6f*,?eLT should be done later．
4 2 Ihe main ecological factors influencing the diurnal variation of Pn and Tr
Along with the results of several other studies，the diurnal courses of Pn for higher plants
(especially C3 planls)~vere two—ridged curves with visible phenomenon of midday depression of
pholosynthesis(Hedges 1967，Xu，Xu＆ Shen 1990，Xu，Zhang＆ Zhang 1992)．Different
from ot hers，the first peak value of C． pgaeco．T appeared earlier and the midday depression of
pbotosynt hesis was olore distinct．These characteristics indicated that the PAR was the lim iting
factor influencing the diurnal variation of Pn r this plant．For example，on sunny days。when
the PAR increased suhstantially from about 1 80 to 900 t~molm-Zs at 7：O0～ 8：O0，approaching to
tile fight saturation point of C． ， “ m r，tile first peak value of Pn appeared．Then．with the
PAR increasing fronl l 250 at 9：00 to 2 260~molm‘ s‘ at 13：00，which exceeded the light setu—
ral ion point substantialy，adding the effect of high temperature (Ta 4 1．9 ，TI 49．5。C)，the
phc~os ym hetic enzynle in the leaf samples became inactive，CO2 assimilation efficiency lowered，
which leads to a sharp de~end of Pn，thus visible midday depression of photosynthesis appeared、
AI 16：00～ 1 7：00，the PAR decreased nearly to the light saturation po int of this plant again，
then the second Pn peak value emerged．
No doubt 1【lal the Tr 0f C． praeco．r was closely correlated to the influenee of Ta and TI．
Fig．6 and Fig．2 shc~wed that the diurnal course of Tr，Ta and TI approximated the sme，that is
to say，i hc Tr 0f C．praectzr varied correspondingly with the fluctuation of Ta and T1，when the
Ta and T1 rose，Tf increased simuhaneously．Yet the peak value of Tr appeared later thBn that
0f Ta and TI．()n sunny days，Ta was high with a wide fluetuation and the differentiation be—
tween Ta and T1 was high，thus the Tr was also high with a wide fluctuation．On cloudy days，
the Ta was low aoc【varied in a smalI range．and the differentiation between Ta and Tl was Iow ，
so did 1he Tr．
To state succinctly，PAR and Ta were two leading influential factors limiting the variation
f)I Tr and Pn for C． praevo,r．This plant was very sensitive to intense light and high tempera—
ture t)n the condition of a high temperature above 40 C and a intense light beyond its light sat—
uration point，its photosyntlactic capacity was weakened greatly with a manifestation of high
transpi ration and water loss． A sharp descend on Pn can be observed．
Here is necesary io point out that the other factors such as Rh．Cc must not to be jgnored
on influencing the cliurnal variation of Pn and Tr for C．praecox but their influence was not so di—
reel and noliceahle as PAR and Ta did．
Acknowledgements：W e gratefuly acknowledge the Edueation Comm ittee of Hunan Province for
its support．The C1—30]PS was bought with a loan from the W orld Bank．
5 Literature Cited
[1]Hierhuizen，J F ＆ R O Slatyer Agri~．M eteord．1965，2：259～ 270
[2]Clcn．G~X，J I i＆ H M Li et a1．Preliminary stusies 0n phytoecoh：lgiea|features of w Jntersweet(Ch~nanam
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58 广 西 植 物 2O卷
thus／,i (， u )com m unity in northwest Hunnn Province
[3] Chen，S-G ＆ Q s Yang． Flawer bud differentiation
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““ yt J Jf 川 Sinica，l9叭 ．20(3)：263～ 271
<53 Guo．1_W ．Y—G Shen，＆ H．W u et a1．Studv on the phot~ ynthetic characteristics of E ulmoides
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[6]Gup．Z H．H—D Zh．＆ Z—A L1 et al Study on the photosynthetic characteristics in 】e~ves Liriodendron
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[7]Hcdges．J r)P~dte rlqs of photosynthesis under natural environment condltlons[J]．Ec,dogy．1 967，48：234
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[8]Jiang-Y．I{一T 】，l Flma Re epublicae popularls Sirfcae 1979，30(2)：1～ 10．Science Press．Beijlng．
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[1() l J，“一X Chert ＆ M 【 1 et ，¨．Preliminn ry researsh on species diversity characteristics ot the typical m-
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and E小 e~l,nent，I 997．6(2)：I2～ 1 6
[IJ]I i【I．Y—D·J l i S J—X Shi A Preliminary Study on the Light Respon~ Curve and Diurnal Variation of Net
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[12]W u，( h] ＆ N—Z Hu Studl s on the flower form and blooming eharacterlstics of the wintersweet．Acta H D_
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[13]Xu，B—F．P—Y Yang＆ Y—L Xu et ．Study on photosynthetic property of high yield cotton in the south of
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(143 Xu—D—Q—B—J Xu Y—G Shen Diurnal varltltion of photosynthetic efficiency in C3 plan,．Acta Phyta坤 ·
iologu：a Si删 “． 1 990，16(1)一1～ 5
[1 5]Xu·D—Q ，Y—Z Zhang＆ R—X Zhang Photoinhibitlon ot photosynthesis in plants．Plant Physiology C ·
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[16]Zhao—T一【 et at．Chinese Calycanthaceae．Henan Sc ience and Technology Publishing H0use．Zhengv~ou．
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让 一
蜡梅光合与蒸腾速率 日变化的初步研 究
李 菁，刘应迪 ，陈功锡，陈 军，朱杰英
t吉首大学生态研究所．湖南吉首 416000)
& 『．7 ．g
．I7磊f
摘 要 ：对野生蜡梅在不同天气 中的净光台速率(Pn)和蒸孵速率 (Tr)日变化及其与环境因子的关
系进行丁初步研究 ．结果如下 ：(1)蜡梅在晴天和 阴天的 Pn日进程均呈一双峰型曲线 。但晴天的两
个峰值 比在阴天 出现要早 ，Pn的总体水平要高于阴天 ，且在午后发 生明显的光台。午休”琨象．(2)
Tr在晴天蚺 日变化呈单 峰型曲线 在午 后强光和高温条件下 ，n 可高达 10mmol H O n一 以上 。
在『判天 ，Tr日进程 波动很小，且 蒸孵作用做弱，全天大多保持在 0．8mmo[HzOm s 以下的水平 。
(3)在 光 台有 效 辐 射 (PAR)为 81}【j～ 900}~mol m ，大 气 温 度 (TA)28℃左 右 、相 对 湿 度 (RH)约
75 的条件下 ，野生蜡梅的 Pn可高选 23．6}~mol CO in s 。但蜡梅 的光饱和点与光补偿点均较低 ．
分 别约 为 901 J盯u0I nl。’s 和 2( im~ol nl s一。(4)PAR和 TA是影响蜡梅光台 与蒸孵速率 日进程的主
导生 态因子。蜡梅耐强光和高温反应敏感。在超过光饱和点且气强高选 42 C以上时 ．其蒸孵作用强
烈 ．能 转换与水分利用效率 (wUE1大大降低，光台能力碱弱 ．导致 Pn急尉下Iij}。
关键词：畦L握；逢 宣萎宴；藿瞳速塞．日萼 t l习L ．P冉
中 圄 分 类号 ：Q945．19 文赫 标识 码 ：A
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