全 文 ：云南大学学报 (自然科学版) 　2002 , 24 (1):56～ 61 CN 53-1045/N　ISSN 0258-7971
Journal of Yunnan University
Effect of Soil K Supply and Terminal Drought on Seed Yield
and Pod Set of Narrow-leafed Lupin
LIU Fei-hu1 , Nancy Longnecker2
(1.Department of Biology , Yunnan University , Kunming 650091 , China;
2.Centre for Legumes in Mediterranean Agriculture , The University of Western Australia , Nedlands , WA 6907 , Australia)
Abstract:This experiment investigated if adding soil K could reduce the influence of terminal drought on lupin
seed yield.Narrow-leafed lupin(Lupinus angustifolius L.mutant Danja abs-)was g rown in a glasshouse with 3 lev-
els of K application (0 , 15 and 60 mg·kg -1).Drought treatment , keeping the soil w ater content at 40%—50% of
field capacity by weighing the pots , kept on for 14 d starting at the beginning of flow ering on the top branches , no wa-
tering afterw ards.Application of K increased seed weight , the number of seeds per pod on the la teral branches and the
number of pods on the main stem , resulting in increased seed yield , but did not affect harvest index.Increasing K sup-
ply increased above-ground biomass , K+ concentration in shoot and main stem seed , and the sucrose concentration in
sap from young pods on the main stem , w hile decreased leaf w ater potential and osmotic po tential.Terminal drought
reduced seed yield via a reduced seed yield of the lateral branches.Terminal drought mainly decreased seed weight and
the number of pods on the la teral branches , as well as above-g round biomass , although it did not affect the number of
seeds per pod and harvest index.Meanwhile , terminal drought reduced leaf water potential but not osmotic po tential.
The results suggest that K does no t compensate for the negative impact of terminal drought on seed yield of narrow-
leafed lupin in this experiment.
Key words:narrow-leafed lupin;pod set;seed yield;soil K supply;terminal drought
CLC number:S 529　　Document code:A　　Article ID:0258-7971(2002)01-0056-06
　　Narrow-leafed lupin is an important crop in
Aust ralia ,Russia and Poland[ 1] .It has a variable and
low harvest index and seed yield in the Mediter-
ranean envi ronment of Western Aust ralia due to f re-
quent terminal drought during seed filling[ 1—3] .Ter-
minal drought shortens pod and seed filling peri-
od[ 1] , and decreases pods per plant and seeds per pod
w ithout inf luence on seed weight[ 2] .Po tassium (K)
plays a key role in photosynthesis ,water and carbon
diox ide regulation , protein synthesis and the trans-
po rt of sugars to seeds[ 4] .Po tassium application im-
proves drought tolerance in maize , tea plants and
some roo t crops
[ 5—7] .However , there are few reports
on the inf luence of K on grow th and yield of narrow-
leafed lupin , o r specifically the effect on lupin toler-
ance to terminal drought.
This study examined the interactions of K sup-
ply and drought on w ater status , plant grow th and
seed yield of narrow-leafed lupin.
1　Materials and method
This experiment was carried out at The Uni-
versity of Western Australia , using a narrow-leafed
lupin mutant-Danja abs-(Lupinus angusti folius L.
cv Danja).The abs-mutant senesces normally , but
does not abscise any organs , making it ideal for in-
vestigating harvest index
[ 8] .A complete facto rial de-
sign of 3 levels of potassium (0 , 15 , and 60 mg·
Received date:2000-03-20
kg-1 , termed K0 , K15 , and K60), and 2 w ater t reat-
ments(adequate w ater ,70%—100% of field capaci-
ty throughout the experiment and drought , 40%—
50% of f ield capacity during the pod setting), was
used with 5 replicates of each treatment.
1.1　Plant culture　Each undrained pot contained
6 kg of Lancelin sandy soil(0.5% of to tal K and 28
mg·kg -1 of K by HCO3), added w ith the appropri-
ate K2SO4 solution and basal nutrients(mg·kg-1)
(Ca(H2PO4)2·H2O 66.7 ,MgSO4·7H2O 19.9 , Cu-
SO4·5H2O 2.13 , ZnSO4·7H2O 4.97 , MnSO4·H2O
9.94 ,CoSO4·7H2O 0.36 , Na2MoO4·2H2O 0.18).
Seven seeds per pot were sow n early in September
and inoculated w ith w ater suspension of rhizobia
(Bradyrhizobium lupinii strain WU425).Three
seedlings were lef t per pot af ter thinning w hich gave
a population densi ty of 60 plants/m 2 on the bench.
Alkathene beads w ere used as mulch.Plants were
g row n in a g lasshouse under natural lig ht (tempera-
ture 22 —23/30—33℃night/day)and w atered dai-
ly to maintain soil moisture content at 75%—100%
of field water capaci ty until drought t reatment start-
ed.The grow th season w as from September to De-
cember.
1.2　Terminal drought treatment　Drought t reat-
ment started at the beginning of f low ering of the top
branches.Half of the pots(drought t reatment)were
w atered twice a day to keep the soil w ater content at
40%—50% of field capacity by weighing the pots.
This lasted for 14 d , no watering afterw ards.Other
pots(control)were watered tw ice a day to maintain
the soil water content at 70%—100% of field ca-
pacity .
1.3　Data collection　The measurements w ere the
above-g round biomass , seed yield , harvest index ,
100-seed w eight , the number of pods per plant and
seeds per pod , K concentrations in the whole shoo t
(sampled at the late flow ering stage of main inflores-
cence)and in the seeds of main stem (using HNO3/
HClO4 digestion and atomic absorption spectrometry
determination), sucrose concentration in sap from
young pods on the main stem (the sap w as collected
by cut ting of f the tip of the fi rst pod on every plant ,
and measured w ith a 0%—28% sugar ref ractome-
ter), leaf w ater potential(the top main stem leaves
at same posi tion w ere tested for dif ferent t reatments
by using a pressure bomb at 14 —15 pm for different
t reatments) and osmo tic po tential (using a Fiske
ont-ten Osmometer , the same leaves as for w ater po-
tential test)during drought treatment period.
2　Results and discussion
2.1　Seed yield and yield components　Added soil
K supply increased seed y ield per plant by 11%
(K60 over K0),due to an increased seed yield of the
main stem.In contrast , terminal drought decreased
seed y ield per plant by 10%, via decreasing seed
yield on the lateral branches(Tab.1).This is under-
standable since i t w as more than 20 d af ter the vig-
o rous flow ering stage on the main inf lo rescence that
the plants started being subjected to the drought
w hen the lateral branches started flow ering .Drought
caused seed y ield reduction regardless of the levels of
K supply in the soil.This indicates that increased K
supply does not improve drought tolerance of lupin
in terms of seed yield in the experiment.
Neither K nor terminal drought inf luenced the
number of pods per plant (Tab.2), with the excep-
tion that K60 treatment increased the number of
pods over K15 on main stem under the terminal
drought condit ion.
Added K increased the number of seeds per pod
for the w hole plant by increasing the number on the
lateral branches rather than on the main stem.Ter-
minal drought did no t influence the number of seeds
per pod(Fig.1a).
Increasing K supply increased the weight of
seed of the w hole plant by increasing that on the
main stem o ther than on the lateral branches (K15
over K0;Fig.1b).Further increasing K supply did
not further increase seed weight.Terminal drought
decreased the w eight of seeds on bo th the main stem
and the lateral branches ,which did not consist with
previous study
[ 2] .The decrease of seed weight on the
main stem caused by terminal drought suggested
that the late g row th period is also important to seed
development of the main stem .It is w orthy of fur-
57第 1 期　　　　　　　　刘飞虎等:增施钾肥和末期干旱对白羽扇豆结荚和种子产量的影响
ther study to understand why the plants receiving 15
mg·kg -1 produced the largest seeds(the same phe-
nomenon was observed in the other experiment car-
ried out by the authors).
　　Tab.1 Effect of K supply and terminal drought on lupin seed yield(g)per plant.Drought(40%—50% of field w ater capaci-
ty);Control(70%—100% of field water capacity)　　　　　　　　　　　　　　　　　　　　　　　　　g
T reatment
Main stem Branches Whole plant
K01 K152 K603 K0 K15 K60 K0 K15 K60
Drought 2.3bA 2.6bA 3.0aA 1.6aB 1.6aA 1.3aB 3.9bB 4.2abA 4.3aB
Control 2.4bA 2.6abA 3.0aA 1.9aA 1.9aA 1.8aA 4.4bA 4.5abA 4.9aA
　　1—No K added to the soil;2—15 mg· kg-1 added;3—60 mg· kg-1 added.
Capi tal A or B is used to mark the signif icant dif ference between terminal drough t t reatment and control in each column.
Low ercase a or b is used to mark the signif icant diff erence betw een di fferent levels of potassium treatments in each row underneath main stem ,
b ranches or w hole plant respectively.
Tab.2 Effect of K supply and terminal drought on lupin pods per plant.Drought(40%—50% of field w ater
capacity);Control(70%—100% of field w ater capacity)
T reatment
Main stem Branches Whole plant
K01 K152 K603 K0 K15 K60 K0 K15 K60
Drought 3.9abA 3.6bA 4.3aA 4.4aA 3.7aA 3.5aA 8.3aA 7.3aA 7.8aA
Control 3.9aA 3.5aA 4.0aA 4.6aA 4.1aA 4.0aA 8.5aA 7.6aA 8.0aA
　　1—No K added to the soil;2—15 mg·kg -1 added;3—60 mg·kg -1 added.
Capi tal A or B is used to mark the signif icant dif ference between terminal drough t t reatment and control in each column.
Low ercase a or b is used to mark the signif icant diff erence betw een di fferent levels of potassium treatments in each row underneath main stem ,
b ranches or w hole plant respectively.
　　Fig.1　Effect of K supply and terminal drought on lupin seeds per pod(a)and seed weight(b).D— terminal drought(40%—50%
of field capacity);N —normal water regime throughout the experiment(70%—100% of field capacity)
2.2 　Harvest index 　Neither K nor terminal
drought affected harvest index in general(Fig.2).
However , the plants receiving 0 mg·kg-1 had higher
harvest index than those receiving 60 mg·kg-1.The
same trend w as also observed in the other experiment
carried out by the authors.This might be the result
of plant self-regulation under the condition of low
biomass production(caused by K deficiency , see be-
low), i.e.of fsetting low biomass by partitioning rela-
tively more assimilate into the reproductive organ.
58 云南大学学报(自然科学版)　　　　　　　　　　　　　　　　第 24 卷
But this phenomenon w as not visible under the con-
di tion of terminal drought.
2.3 　Above-ground biomass　Added K increased
biomass production(Fig.3)which implied that suf-
f icient K supply in the soil could accelerate the as-
similate accumulat ion or , in contrast , insufficient K
supply inhibited assimilate product ion and this w as
w orsened as soil K supply decreased.This was w hy
the lupin seed yield w as increased under suff icient K
supply although the harvest index w as as low as or
even low er than that under insuf ficient K supply
(Fig.2).Terminal drought caused a decrease of
biomass by 1.1 g/plant (8%), among which , the
seed yield decreased by 0.4 g/plant (9%), pod wall
w eight by 0.4 g/plant(12%),but the shoot w eight
(excluding pods) only decreased by 0.3 g/plant
(5%).This meant a greater inf luence of terminal
drought on the g row th of reproductive organs than
on the g row th of vegetative org ans , or terminal
drought inhibited the t ranspo rt of assimilate f rom
vegetative o rgans into reproductive o rgans.
2.4　Tissue K concentration and sucrose concentra-
tion 　K concentrations in the seeds on the main
stem and in the w hole shoots (sampled at the late
flow ering stage of the main inf lorescence)increased
as K supply increased (Fig.4a), but only shoot K
concentration showed a correlation w ith the level of
K supply .This meant a g reater influence of soil K
supply on K concentration of shoots.Furthermore ,
the plants receiving 15 mg·kg-1 y ielded the same as
the plants receiving 60 mg·kg-1 , although the for-
mer show ed K deficiency symptom w ith a K concen-
trat ion in the shoo ts less than 0.80%(<0.9% is
considered as K deficiency[ 9] ).Possibly the lupin
plants could tolerate some deg ree of K def iciency in
terms of g row th of reproductive organs.
The sucrose concentration in sap of young pods
on the main stem also increased as soil K supply in-
creased(Fig .4b), which suggested that sufficient K
supply in the soil could increase the assimilate pro-
duction and/o r i ts t ranspo rtation into the reproduc-
tive organs.This might partially explain the biomass
increase caused by increased soil K supply .
2.5　Leaf water potential and osmotic potential
Added K reduced the leaf water po tential by
13%, while the terminal drought caused a 7% de-
crease(Fig.5a).This implied that the mineral ions
(like K+)concentration of plant tissue (Fig.4a),
rather than the w ater status of plant tissue , had a
closer connection to the leaf water potential.There-
fo re the former is mo re important in adjusting leaf
w ater potential under this condition.
　　Fig.2 Both K and terminal drought did not affect the harvest
index.D— terminal drought(40%—50% of field ca-
pacity);N—normal water regime throughout the ex-
periment(70%—100% of field capacity).
Fig.3 Effect of K supply and terminal drought on above-
g round biomass.D— terminal drought(40%—50% of
field capacity);N —no rmal w ater reg ime throughout
the experiment(70%—100% of field capacity).
59第 1 期　　　　　　　　刘飞虎等:增施钾肥和末期干旱对白羽扇豆结荚和种子产量的影响
　　Fig.4 Effect o f K supply on tissue K concentration(a)and sucrose concentration in sap of y oung pods on the main stem(b).
(Seed w as sampled on the main stem after harvest;Shoot sampled at the late flowering stage of the main inflo rescence)
　　F ig.5 Effect of K supply and terminal drought on leaf water po tential(a)and o smotic po tential(b).D— terminal drought
(40%—50% of field capacity);N —no rmal water regime throughout the experiment(70%—100% of field capacity)
　　The osmotic potential of leaf sap decreased as
the soil K supply increased , but drought did no t af-
fect osmo tic potential(Fig.5b).This is reasonable
since the osmotic po tential is mainly controlled by
the mineral ions , especially K+ in the tissue , while
the w ater content in the t issue is not as important.
Morgan observed that high osmoregulation w as
largely (78%)due to po tassium accumulat ion in
w heat[ 10] .While tolerance of w ater st ress usually in-
volves the development of low osmotic potentials ,
which characterizes many plant species[ 11] .The de-
crease in osmot ic potential due to increased soil K
supply (consequently higher K+concentration in the
tissue)in this experiment had no favorable function
for reducing the deleterious ef fect of drought on the
plants , probably because the plants suffered only a
short period of terminal drought.In the fact , there
are only a few reports that provide evidence of a pos-
itive association between osmo regulat ion and dry
mat ter production or grain yield[ 11] .
3　Conclusion
Increased soil K supply could increase the seed
yield per plant of narrow-leafed lupin via increasing
seed size , the number of pods on the main stem and
seeds per pod.This resulted f rom an increased
biomass production due to a faster and/or more as-
similate production induced by sufficient soil K sup-
ply .The decreases in leaf w ater po tential and osmo t-
ic potential caused by added soil K supply is not well
know n for their benefits to lupin g row th and devel-
opment.The lupin plants could tolerate some deg ree
of soil K deficiency in terms of seed yield.
Terminal drought decreased lupin seed yield by
decreasing seed size and the number of pods on the
lateral branches.The phy siolog ical mechanisms of
decrease in leaf water potential caused by terminal
drought need further investigation.
Acknowledgements:The authors g ratefully
thank Dr Caixian Tang , Dr Roya Niknam , Dr Lor-
60 云南大学学报(自然科学版)　　　　　　　　　　　　　　　　第 24 卷
raine Osborne , Dr Tim Colmer , Dr Zed Rengel for
their kind help in this experiment.
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[ 4] 　MARSCHNER H.Mineral nutrition in higher plants
[ M] .London:Academic Press inc LTD , 1986.
[ 5] 　YAPA L G G , WANASUMDARA W M U N , PUN-
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增施钾肥和末期干旱对白羽扇豆结荚和种子产量的影响
刘飞虎1 , Nancy Longnecker2
(1.云南大学 生物系 , 云南 昆明　650091;
2.西澳大利亚大学 干旱农业区豆科作物研究中心 , 西澳大利亚州 佩斯　6907)
摘要:试验探讨通过增施钾肥减轻末期干旱对白羽扇豆产量影响的可能性.温室盆栽窄叶白羽扇豆
(Lupinus angusti folius L.),施钾水平为 0 ,15 ,60 mg·kg -1.于顶部分枝始花期开始干旱处理 ,用称重法使
土壤含水量控制在田间持水量的 40%—50%,持续 14 d 后停止浇水.对照保持田间持水量的 70%—
100%,与干旱处理的同时停止浇水.结果表明 ,施钾能增加地上部生物产量 、粒重 、侧枝上的每荚种子数和
主茎结荚数 ,因而提高产量;但对收获指数无影响.施钾还增加豆苗及主茎种子的钾含量及主茎幼荚汁液
的蔗糖浓度 ,但降低叶片水势和渗透势.末期干旱降低地上部生物产量和粒重 、减少侧枝结荚数导致侧枝
种子产量降低 ,从而使整株产量下降;但不影响每荚粒数和收获指数.末期干旱降低水势 ,但不影响渗透
势.在本试验中 ,施钾不能消减末期干旱对窄叶白羽扇豆种子产量的影响.
关键词:窄叶白羽扇豆;土壤施钾;末期干旱;结荚;种子产量
61第 1 期　　　　　　　　刘飞虎等:增施钾肥和末期干旱对白羽扇豆结荚和种子产量的影响
作者简介:刘飞虎(1958-　),男 ,湖南人 ,教授 ,主要从事作物遗传育种和栽培生理生态研究.