全 文 ：J. Resour. Ecol. 2015 6 (4) 269-275
DOI:10.5814/j.issn.1674-764x.2015.04.011
www.jorae.cn
July, 2015 Journal of Resources and Ecology Vol.6 No.4
Received: 2015-05-21 Accepted: 2015-07-08
Foundation: the National Science and Technology Support Program (2012BAC16B01,2012BAC16B02) and
National Natural Science Foundation of China (41172313).
* Corresponding author: HE Chengxin. Email: 838841223@qq.com; hecx@gxib.cn.
Karst Ecosystem
Physiological Effect on Hylocereus undulatus and Hylocereus
undatus under Simulated Karst Soil Water Deficiency
HUANG Yuqing1, YUAN Weiyuan2, MO Ling1, XU Guangping1, ZHANG Zhongfeng1, ZENG Danjuan1,
HE Chengxin1* and GU Daxing1
1 Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain, Guangxi Institute of Botany, CAS, Guilin 541006, China;
2 Guangxi Bobai Middle School, Bobai 537600, China
Abstract: Dragon fruit (Hylocereus undulates) was planted in a large area of karst region in recent years. To
understand whether karst drought may impact on its physiological process is important and useful for planning
and management of this fruit. In this study, we contrasted with a relative species Hylocereus undatus, and set
up experiment to study physiological and biochemical trait and its response to different karst soil water level
deficiency, so as to understand the mechanism of H. undulates and H. undatus in adaptation to karst drought
condition. The results showed that, trends of physiological and biochemical response to drought was similar
between two species. With the intensive of soil water deficiency, such toxin substance as malonaldehyde
(MDA) increased, but meanwhile, two protective enzymes superoxide dismutase (SOD) and peroxidases (POD) and
osmotic adjustment Proline (Pro) increase as well. Under relative water content (RWC) >50% condition, the
enzyme can effectively protect the cells from toxin MDA injure, and Pro can also maintain the water needs
through osmotic adjustment. However, under RWC < 40% condition, protective enzymes were not enough for
cleaning MDA. Biomass was largest under RWC=70%–80%, with low root shoot ratio and high aboveground
biomass. Biomass significantly decreased under RWC 30%–40%, which decline by 73.28% and 73.56% in H.
undulates and H. undatus respectively. Therefore, RWC=70%–80% would be an optimal soil moisture while
developing dragon fruit in karst, which is favor to fruit production. Under moderate drought e.g. RWC=50%–60%,
plants may regulate by metabolic process and balance unfavorable substance, but it allocated much more
biomass to root, reduced the aboveground biomass, which is not advance for fruit production.
Key words: Hylocereus undulatus and Hylocereus undatus; physiological effect; karst; drought
1 Introduction
Dragon fruit (Hylocereus undulatus, HD) and Hylocereus
undatus (HN) belong to Hylocereus genus and Cactus
family. They are closely relative species, drought tolerance,
climbing and succulent, usually considered to be H. undatus
species by some literature (Elobeidy 2006; Mizrahi et al.
2002), in which HD can produce big sweet juicy fruit but HN
can not. HD is a very popular new tropical and subtropical
cultivar fruit, which was introduced to mainland China from
Taiwan Province in 1999, and rapidly expanding in recent
years growing in Hainan, Guangdong, Fujian, Guangxi and
Yunnan provinces. HN original distribution in Mid-America
to northern of South America, widely cultivated throughout
the world. HN was introduced to China in 1645 and has
dispersal as wild species in the southwest of Guangxi,
southern Guangdong, southern Fujian, Hainan and Taiwan
(Zeng 1999). HN commonly climbs in wild on bare karst
rock, tolerance drought in Southwestern Guangxi. As HN’s
flower is edible, it is planted for commercial use in the last
10 years.
In karst region of South China, HN is considered to
adapt to extreme drought and in high pH condition. Due to
the similarity of HD and HN in biological properties, we
started to introduce HD to karst rocky desertification area in
2012. HD can grow well in karst with high fruit yield and
Journal of Resources and Ecology Vol.6 No.4, 2015270
good quality. It becomes an important local fruits and is
promoted to expand, achieving very good economic and
ecological benefits (Lu et al. 2012). However, periodic and
seasonal drought commonly occurred in south west rocky
desertification area in China, which is the main constraint
factor to influence rehabilitation of the ecosystem. Therefore,
results by comparing studies on ecophysiology of two
species will help to make a strategy for planting dragon fruit
using HN’ habitat as reference.
Plant metabolic response to drought is basically
similar (Pan 2001), which may appear a variety of
physiological processes, including change of chlorophyll
of photosynthetic capacity (Liu et al. 2012; Brodribb and
Holbrook 2004), change of membrane lipid peroxidation
such as malondialdehyde (MDA), change of the plant
self-repair system such as producing lipid peroxidation
and protective enzyme activity, and change of cellosmotic
adjustment such as free proline (Pro) (Valentovic et al.
2006; Shao et al. 2008; Zhang et al. 1996; Ren et al.
2015). Although HD is a Cactus species belonging to
Crassulacean acid metabolism (CAM), which stomatal
close during daytime thereby to require few water that the
plant can adapt to drought environment. But whether is soil
water deficiency impact on physiological process of these
two species? How are they response to drought stress? Is
exotic species HD similar to native HN in responding to
drought? There are rare data reported in this field by now.
In this study, we set up pot experiments with treatment of
four water level water content to identify the physiological
response of HD and HN, that to provide scientific basis for
drought resistant cultivar improvement, and HD planning
and management.
2 Materials and methods
2.1 Experimental site
Experiment was set up in a plastic greenhouse locating
in Guangxi Institute of Botany, Yanshan District, Guilin
city, 25˚01′N and 110˚17′E, 140m alt. It is subtropical
monsoon climate, with average annual rainfall 1900
mm; annual average sunshine is about 1550 h, and annual
average temperature 19℃, Haplic acrisol.
2.2 Materials and treatment
Materials of HD were taken from Nanning nursery, 1 year
old seedlings (non karst area); HN seedling was from
wild in karst area of Pingguo County, Guangxi province,
China. Uniform seedlings were transplanted in plastic pots
of inner diameter 28 cm, height 33 cm in March 2008. Each
pot was planted one seedling, total 80 pots. The soil was
taken from karst, mix (average soil bulk density =1.21 g
cm-1, pH=7.43, the field water capacity =27.3%). Plants
was irrigating every week from March to August to ensure
seedling survival and growth. Four water-level treatments
were designed basing on karst natural soil water variation.
Seedlings of two species were randomly divided into 4
groups for 4 water treatments, 10 replications. Water level
was designed as relative water content (percentage of field
water capacity, FWC) as below:
Ck: 90%–100% of FWC,
means water content =24.6%–27.3%
A: 70%–80% of FWC,
means water content =19.1%–21.8%
B: 50%–60% of FWC,
means water content =13.7%–16.4%
C: 30%–40% of FWC,
means water content =8.2%–10.9%
Soil water content was measured using WET-2-K1
(Delta-T, Britain) and deficient amount of water was
calculated and added to make sure it was kept in controlled
water level. Water treatment was carrying in for 28 days.
2.3 Sampling and testing
2.3.1 Sampling time
Chlorophyll (Chl), malondialdehyde (MDA), protective
enzymes such as superoxide dismutase (SOD) and
peroxidases (POD) and osmotic adjustment Proline (Pro)
are usually used as physiological indicators to present plant
drought resistance (Li et al. 2000; Zhang 2003)
Sample for POD and SOD was collected on the day of 28
after water treatment; other sample was collected on days of
0, 7, 14, 21 and 28 after water treatment.
2.3.2 Test methods
The chlorophyll a and b (Chl a and Chl b) were determined
by acetone-spectrophotometric method, MDA by
thiobarbituric acid method, Pro by ninhydrine method,
POD activity by guaiacol method (Li et al. 2000) and SOD
activity by nitroblue tetrazoliumfour (NBT) reduction
method (Lin et al. 1984).
2.4 Statistics
Significant difference test using SPSS One-way ANOVA
method and LSD (p =0.05).
3 Results
3.1 Effect of water deficiency on chlorophyll content
The change of chlorophyll under different water
gradient level in HD and HN was different (Fig. 1). Chl a
and Chl b did not present significant difference between
two species in the beginning of treatment. In the prolonging
of treatment time, all Chl a, Chl b and Chl(a+b) of HD
did not change significantly under RWC >50% except
day 28 in RWC=50%–60% treatment (B) (P<0.05); while
RWC=30%–40% (C), Chl a, Chl b and Chl(a+b) presented
significant decrease beginning on day 14 after treatment (P<
0.01). HN, however, simply in RWC=50%–60% treatment,
Chl a, Chl b and Chl(a+b) presented significant increase
beginning on day 14. The result indicates that HD can be
tolerant of drought, but too low water (RWC=30%–40%)
may impact on its Chl. On the contrary, low water may not
HUANG Yuqing, et al.: Physiological Effect on Hylocereus undulatus and Hylocereus undatus under Simulated Karst Soil Water Deficiency 271
species was similar, in which MDA content increased with
soil moisture decreasing and prolong of drought (Fig. 2a,
2b). Compared with the sample of day 0, MDA content in
RWC=70%–80% treatment began significantly decreasing
on day 21, in RWC=50%–60% treatment on day 14, while
in the driest RWC=30%–40% treatment, on day 7. The
result indicated that the more severe deficiency of soil water
the earlier MDA began decreasing after treatment. In RWC=
30%–40% treatment, MDA of both species was reached
the peak on day 14, but then mildly decreased on day 21
and slowly increased after. Peak MDA value of HD and
Co
nc
en
tra
tio
n o
f
M
DA
(μ
m
ol
g
-1
FW
)
Days after treatment (d)
10
8
0 7 14
B
A
2821
6
4
2
HN
C
CK
b
Co
nc
en
tra
tio
n o
f
M
DA
(μ
m
ol
g
-1
FW
)
Days after treatment (d)
10
8
0 7 14
B
A
2821
6
4
2
HD
C
CK
a
Fig. 2 MDA of HD and HN species response to water
deficiency and prolong time.
Co
nc
en
tra
tio
n o
f
M
DA
(μ
m
ol
g
-1
FW
)
Days after treatment (d)
8
0 7 14 2821
6
4
2
HD
c
HN
Fig. 1 Chl a, Chl b and
Chl(a+b) of HD and
HN species response
to water soil level and
prolong time.
Co
nc
en
tra
tio
n o
f C
hl
a
(m
g g
-1
FW
)
Days after treatment (d)
4.0
3.0
0 7 14
B
A
2821
2.0
1.0
0.0
HD
C
CK
a
Co
nc
en
tra
tio
n o
f C
hl
a
(m
g g
-1
FW
)
Days after treatment (d)
4.0
3.0
0 7 14
B
A
2821
2.0
1.0
0.0
HN
C
CK
b
Co
nc
en
tra
tio
n o
f C
hl
b
(m
g g
-1
FW
)
Days after treatment (d)
1.2
0 7 14
B
A
2821
0.8
0.4
0.0
HD
C
CK
c
Co
nc
en
tra
tio
n o
f C
hl
b
(m
g g
-1
FW
)
Days after treatment (d)
1.2
0 7 14
B
A
2821
0.8
0.4
0.0
HN
C
CK
d
Co
nc
en
tra
tio
n o
f C
hl
a+
b
(m
g g
-1
FW
)
Days after treatment (d)
4.0
3.0
0 7 14
B
A
2821
2.0
1.0
0.0
HD
C
CK
e5.0
Co
nc
en
tra
tio
n o
f C
hl
a+
b
(m
g g
-1
FW
)
Days after treatment (d)
4.0
3.0
0 7 14
B
A
2821
2.0
1.0
0.0
HN
C
CK
f5.0
impact on Chl of HN, and appropriate drought (RWC=50%–
60%) is favorable for chlorophyll synthesis.
3.2 Effect of water deficiency on MDA content
The change pattern of MDA content between HD and HN
Journal of Resources and Ecology Vol.6 No.4, 2015272
HN were 1.07 times and 0.98 times higher than the value
of the day 0. MDA content in HD was significantly higher
than in HN (P=0.011) on day 0, and always higher with the
prolongation of treatment. MDA is one of lipid peroxides,
and is cytotoxic, which may increase accumulation in HD
and HN species after severe drought and prolongation of
over two weeks, resulting in damage of cell. Increasing
value of MDA between in RWC=90%–100% to 50%–60%
and in RWC=50%–60% to 30%–40% approximate equal,
indicating MDA speeding up in RWC=40%–50%.
3.3 Effect of water deficiency on proline (Pro)
The change pattern of Pro content between two species
was similar (Fig. 3). Pro changing curves could be divided
into three groups: (i) In RWC=70%–80% and 90%–100%
treatment, Pro curve was low and flat. Pro value of any
samples did not present significant difference comparing to
day 0. (ii) In RWC=50%–60%, Pro curve was in the middle,
which slightly rose on day 7, dramatically rose on day 14,
and got flat after then. And (iii) in RWC=30%–40%, Pro
was on the top, which had significantly increased in 7 days
(P<0.01), and accelerated from day 7 to day 14, and got flat
after then. Largest difference among these three groups was
on the day 14 and later. Pro of dragon fruit was 9.77 μg g-1
in RWC=50%–60% and 19.19μg g-1 in RWC=30%–40%
respectively, which was 1.70 times and 4.30 times higher
than day 0. While Pro of HN species was 10.69 μg g-1 in
RWC=50%–60% and 16.97 μg g-1 in RWC=30%–40%
respectively, which was 1.37 times and 3.03 times higher
than day 0. Thus, Pro as osmotic regulation substance
greatly varied in succulent stem of HD and HN species
when water was severe deficient in soil, especially in dragon
fruit.
3.4 Effects of water treatment on protective enzyme
activity SOD and POD
After 28 days of water treatment, the change pattern of
POD and SOD along with water level between two species
is similar. Both SOD and POD increased continuously with
RWC decreasing from 90%–100% to 50%–60%, which the
value at each sample time presented significant difference (P
< 0.01). However SOD and POD significantly decreased in
RWC=30%–40%, comparing to RWC=50%–60%. (Fig. 4),
the peak value of SOD increased by 187.26% in HD species
and 116.24% in HN species comparing to the minimum
values, while for POD the number was 88.69% in HD and
127.70% in HN. Thus, with the occurrence of soil drought,
HD and HN species can generate large amount of protected
enzyme to mediate the active oxygen free radicals. This
function was strongest in RWC=50%–60%, but decreased
in further drought condition, yet it still maintained in high
level.
3.5 Effects of water treatment on biomass
With the decline of soil moisture, total biomass of two
Fig. 3 Pro of HD and HN species response to water
deficiency and prolong time.
Co
nc
en
tra
tio
n o
f
Pr
o
(μ
g
g-
1 F
W
)
Days after treatment
20
15
0 7 14 2821
10
5
0
HD−CK
25 HN−CK
HD−A
HN−A
HD−B
HN−B
HD−C
HN−C
species showed increased first and then decreased (Fig. 5a).
Maximum was peak in RWC=70%–80% with significant
higher than other RWC treatments. Biomass continuously
declined from RWC=70%–80% to 30%–40%. Minimum
value of HD and HN (occurred in RWC=30=40%
treatment) decreased by 73.28% and 73.56% respectively
comparing to maximum biomass, and decreased by
29.27% and 29.71% respectively while comparing to
saturated water treatment (CK). The root shoot ratio did
not present significant difference between two species (Fig.
5b) under the same water treatment. But root shoot ratio
value could be distinctively divided into two forms: CK
and A treatment-set, B and C treatment-set, which later
treatment-set was significantly and double higher than the
former set. Therefore, for root shoot ratio, turning point
occurred at RWC decreased from 70% to 60%. In RWC
Fig. 4 POD and SOD response to soil water deficiency.
PO
D
a
ct
iv
ity
(μ
.g
-1
.m
in-
1 F
W
)
Treatment
80
60
CK A B C
40
20
0
HD
100
HN
SO
D
a
ct
iv
ity
(μ
.g
-1
F
W
)
Treatment
160
120
CK A B C
80
40
0
HD200
HN
240
HUANG Yuqing, et al.: Physiological Effect on Hylocereus undulatus and Hylocereus undatus under Simulated Karst Soil Water Deficiency 273
>70%, comparative more biological energy might allocate
to the above ground, as a result produce more flower and
fruit, while in RWC <60% relative more biological energy
allocated to belowground as strategy in searching for water.
4 Discussion
Dragon fruit and Hylocereus undatus have thick green
succulent stems, which is rich with chlorophyll. This
Crassulacean acid metabolism (CAM) pathway species is
stomatal closure during day and demand small amount of
water. Content of chlorophyll (Chl) can directly reflect the
plant photosynthetic capacity, and at same time demonstrate
the plant stress statue. Decreasing of chlorophyll infers
progression from functional effect to organ damage under
water stress (Xia 1993). In general, chlorophyll content
may decrease with intension and prolong of drought stress
(Su et al. 2012), Chlorophyll degradation reason is mainly
due to increasing of oxygen activity and hydrogen peroxide
and MDA, and decreasing of antioxidant content, resulting
in chlorophyll protein complexes injury (Jiang and Yang
1994). Our result showed that decreasing of Chla and Chlb
of dragon fruit simply occurred in very dry condition for
2 weeks. According to our observation, many species in
South China had already wilting in 1–2 days under this
drought condition. The result indicates that dragon fruit
is well drought adaptation. Hylocereus undatus however,
chlorophyll was not changed even in severe drought
condition for 28 days, on the contrary, chlorophyll increased
in RWC=50%–60% condition, suggesting that Hylocereus
undatus is good in drought adaptation, in which proper
drought condition can be favorable for photosynthetic
organ.
Active oxygen metabolism is a primary response for
plant to abiotic stresses. Drought stress may result in
the out-of-balance between free radicals generation and
elimination cells which lead to accumulation of free
radical, and thus triggered or intensified the cell membrane
lipid peroxidation, producing MDA (Chandra and Dubey
2010). The level of MDA content reveals the membrane
lipid oxidation and how membrane damage (Peng et
al. 2011). Of both HD and HN species, MDA greatly
increasing with RWC decrease for 28 days, MDA was the
highest in lowest RWC condition (RSWC=30%–40%),
indicating that any drought is possible to cause damage
to cell membrane. But at same time, plant produces
antioxidase system such as SOD and POD which scavenge
active oxygen. SOD is a most protective enzyme system;
catalyze fast-disproportionation-reaction (Zhao et al. 2005;
Zhang et al. 1996). In general, SOD, POD may increase
when the plant is under drought stress, so as to scavenge
active oxygen radicals, thereafter to increase its tolerance to
drought. The stronger drought tolerance the more protective
enzyme activity increases (Talbi et al. 2015; Zhang et al.
2014). SOD and POD in both HD and HN species increased
with RWC decreased, maximum in RSWC=50%–60%,
but then decreased with RWC decreased. This result
indicates that excess drought stress destroys the balance
between oxygen free radical and scavenging, plant reaches
its maximum tolerance that protective enzyme system
activity may decrease. The relationship between SOD and
MDA, POD and MDA were shown in Fig. 6. SOD and
POD quickly rose with increasing of MDA which fitted
exponential function in RWC >50%, and turning point was
at RSWC=50%–60%. This result suggests that protective
enzyme can balance MDA from injure cell membrane in
RWC >50% condition, but this balance may have been
broken in RWC < 40% condition, where protective enzyme
can not scavenge MDA mostly.
Under stress, plant syntheses become weaken but
hydrolysis is enhanced, which may generate soluble sugars,
Fig. 5 Total DM and root shoot ratio response to soil
water deficiency.
Th
e r
oo
t s
ho
ot
rat
io
Treatment
0.10
0.08
CK A B C
0.06
0.04
0.02
HD
0.12
HN
0.14
0.00
b
a
b
aa
a
bb
b
DM
(g
)
Treatment
150
CK A B C
50
0
HD100 HN
a
b bcd
a
c
d e
f
Fig. 6 The relationship between MDA and POD, MDA and
SOD.
SO
D
an
d C
OD
(μ
g-1
m
in-
1 )
MDA (μmol g-1)
200
160
120
80
40
0
0 2 4 86 10
y = 14.124e0.3861x
R2=0.9986
y = 3.5988e0.5261x
R2=0.9911
y = 10.316e0.318x
R2=0.9988
y = 4.9349e0.4094x
R2=0.9845
HD-POD
HN-POD
HD-SOD
HN-SOD
Journal of Resources and Ecology Vol.6 No.4, 2015274
peptides and amino acids by catabolism of macromolecular
compounds. Therefore, osmotic regulation substances
may increase under stress, which can decrease plant
osmotic potential, enable plants to maintain uptake water
for growth (Gong et al. 2004). Our study showed osmotic
regulation substances such as Pro did not change under a
mild water deficiency, Pro slightly rose under moderate
drought, and dramatic increase under severe drought,
suggesting that Pro play an important role in moderate and
severe water deficiency. Pro increase rate was accelerated
at RWC decreased from 50% to 40%. This indicate that
inflection point of generation of Pro is at RWC= 40%–50%,
that hydrolysis enhanced to obtain water. This result is
consistent with generation of protective enzymes and MDA.
Chlorophyll produces organic matter by photosynthesis,
and relocates the organic matter to biomass, analysis above
shows that Chl of dragon fruit decreased significantly
under water severe deficiency condition. Additionally,
some organic matter was use by the secondary metabolism
process due to water deficiency, as a result to reduce the
biomass greatly. Chl of HN species did not decline, but
increased under moderate water condition, this is explained
that the biomass of HN in moderate water condition did not
present significantly difference comparing in saturate water
condition shortage, although drought causing secondary
metabolism process which may use some organic matter
by photosynthesis. Biomass allocation can also explain
the strategy of plant to adapt drought stress. Root shoot
ratio is an important indicator for measuring drought
tolerance. Under water stress, more biomass may allocate
to the underground organs and result into root shoot ratio
increased (Sun and Chen 2000; Heckathom and Deluciae
1996). Our result showed that with water deficiency, trend
of biomass and root shoot ratio changing is opposite. Under
RWC >70%, biomass is big, root shoot ratio is small, while
under RWC <60% biomass is small and root shoot ratio is
big. This suggests that two species allocated more biomass
to the root under drought condition, therefore to reduce
the aboveground biomass, but this is disadvantage to such
economic fruit plant as dragon fruit. Therefore, in order to
obtain good production, soil moisture should be control as
RWC=70%–80%. Instead, too much water can not produce
maximum aboveground biomass.
5 Conclusion
Trends of physiological and biochemical response
to drought were similar between two species under
simulated karst condition. (i) With the increasing of
soil drought, such toxin substance as malonaldehyde
(MDA) increased, but at the same time, two protective
enzymes superoxide dismutase (SOD) and peroxidases
(POD) and osmotic adjustment Proline (Pro) increases. (ii)
Under RWC >50%, the enzyme can effectively protect the
cells from toxin MDA injure, and Pro can also maintain
the water needs through osmotic adjustment. While
under RWC <40%, balance between protective enzymes
and toxin injure was damage. And (iii) biomass, which
transfers from photosynthesis by chlorophyll, decreased
greatly in sever water deficiency. Total biomass was
large under RWC=70%–80% but root shoot ratio was
low demonstrating aboveground biomass was high.
Therefore, RWC=70%–80% would be optimal soil moisture
while developing dragon fruit in karst region which is
favor to fruit production. Under moderate drought e.g.
RWC=50%–60%, plant can regulate by metabolic process
and balance the unfavorable substance, but it allocated much
more biomass to root, that would reduce the aboveground
biomass, which is not advance for fruit production.
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火龙果与量天尺对岩溶土壤干旱的生理响应研究
黄玉清1，袁维园2，莫 凌1，徐广平1, 张中峰1, 曾丹娟1, 何成新1, 顾大形1
1 广西喀斯特植物保育与恢复生态学重点实验室，中国科学院广西植物研究所，桂林 541006；
2 广西博白中学，博白 537600
摘 要：近年来火龙果大面积在岩溶区种植，岩溶干旱是否对其生理过程产生影响，对于规划和管理这种热带水果具有重
要科学意义。本研究通过试验对比研究火龙果及其近缘野化种量天尺的生理生化过程对不同水分水平的响应，阐明这两种植物
的适应干旱机制。结果表明，两种植物随土壤水分下降生理生化变化过程基本一致。随着土壤干旱的加剧，有害物质丙二醛
增加，但同时两种保护酶（SOD和POD）和渗透调节物质Pro也随之增加；在相对含水量>50%，保护酶能有效清除代谢毒素，
Pro也能通过渗透调节维持水分需要；但是当相对含水量<40%时，保护酶的保护功能下降。叶绿素通过光合作用形成生物量，
在相对含水量为70%-80%时生物量最大，此时根冠比小，地上生物量最大；土壤相对含水量为30%-40%时生物量显著下降，两
种植物的降幅分别达到73.28%和73.56%。因此在岩溶地区发展火龙果，土壤水分控制在相对含水量为70%-80%为最佳，有利于
水果产量的形成；中度水分不足，虽然植物通过代谢调节和平衡不利因素，但却分配较多的生物量到根系，降低地上生物量，
从而不利于水果产量的形成。
关键词：火龙果和量天尺；生理影响；岩溶；干旱