Annual growth of the spring ephemeral Erythronium americanum as a function of temperature and mycorrhizal status

Article (PDF Available)inCanadian Journal of Botany 84(1):39-48 · January 2006with 195 Reads
DOI: 10.1139/b05-140
Abstract
The capacity of the spring ephemeral Erythronium americanum L. to grow and absorb nutrient either as nonmycorrhizal (NM) or mycorrhizal (M) plants under the low temperature regime characteristic of its growth period was investigated. Specimens of E. americanum were collected in the field as either NM (early September) or as M plants (late October). Both groups of plants were submitted to different nutrient regimes during the hypogeous growth period at 5 °C, and during the subsequent epigeous growth period conducted at temperature regimes of either 12 °C day : 10 °C night or 17 °C day : 15 °C night. Nutrient regime influenced bulb nutrient content only during the epigeous growth period. The presence of mycorrhizas did not influence nutrient content, but favoured a greater bulb biomass at the final harvest (epigeous growth period), as did the lower temperature regime. Net nutrient uptake was not reduced at lower temperatures and appeared to follow plant demand. These findings confirm that E. americanum is adapted to perform better under a low temperature regime and that mineral nutrition in this species occurs mainly in spring in response to active growth. Arbuscular mycorrhizal fungi benefit E. americanum maybe through less expensive nutrient uptake or sustained carbon sink demand.
Annual growth of the spring ephemeral
Erythronium americanum as a function of
temperature and mycorrhizal status
Line Lapointe and Sylvain Lerat
Abstract: The capacity of the spring ephemeral Erythronium americanum L. to grow and absorb nutrient either as non-
mycorrhizal (NM) or mycorrhizal (M) plants under the low temperature regime characteristic of its growth period was in-
vestigated. Specimens of E. americanum were collected in the field as either NM (early September) or as M plants (late
October). Both groups of plants were submitted to different nutrient regimes during the hypogeous growth period at 5 8C,
and during the subsequent epigeous growth period conducted at temperature regimes of either 12 8C day : 10 8C night or
17 8C day : 15 8C night. Nutrient regime influenced bulb nutrient content only during the epigeous growth period. The
presence of mycorrhizas did not influence nutrient content, but favoured a greater bulb biomass at the final harvest (epi-
geous growth period), as did the lower temperature regime. Net nutrient uptake was not reduced at lower temperatures and
appeared to follow plant demand. These findings confirm that E. americanum is adapted to perform better under a low
temperature regime and that mineral nutrition in this species occurs mainly in spring in response to active growth. Arbus-
cular mycorrhizal fungi benefit E. americanum maybe through less expensive nutrient uptake or sustained carbon sink de-
mand.
Key words: arbuscular mycorrhizal fungi, cool temperatures, Erythronium americanum, mineral nutrition, plant growth,
spring ephemeral.
Re
´sume
´:Nous avons e
´tudie
´la capacite
´de l’e
´phe
´me
`re de printemps Erythronium americanum L. a
`croı
ˆtre et a
`absorber
les nutriments aux basses tempe
´ratures caracte
´ristiques de sa saison de croissance, chez des plantes mycorhize
´es et non
mycorhize
´es. Des bulbes d’E. americanum ont e
´te
´re
´colte
´s sur le terrain, comme plantes non mycorhize
´es (de
´but septem-
bre) ou mycorhize
´es (fin octobre). Les deux lots de plantes ont e
´te
´soumis a
`diffe
´rents re
´gimes nutritifs pendant la phase
de croissance hypoge
´ea
`58C, de me
ˆme qu’au cours de la phase de croissance e
´pige
´e ulte
´rieure, re
´alise
´ea
`des re
´gimes de
tempe
´ratures de 12 8C jour : 10 8C nuit ou de 17 8C jour : 15 8C nuit. Le traitement nutritionnel a influence
´la teneur en
nutriments du bulbe, uniquement durant la pe
´riode de croissance e
´pige
´e. La pre
´sence de mycorhizes n’a pas influence
´la
teneur en nutriments, mais a favorise
´une biomasse du bulbe plus e
´leve
´e en fin d’expe
´rience (croissance e
´pige
´e), tout
comme le re
´gime des plus basses tempe
´ratures. L’absorption nette de nutriments n’a pas e
´te
´re
´duite aux plus basses tempe
´-
ratures et semblait s’ajuster aux besoins de la plante. Ces re
´sultats confirment qu’E. americanum s’est adapte
´afin de
mieux croı
ˆtre sous un re
´gime de basses tempe
´ratures et que la nutrition mine
´rale de cette plante a lieu principalement au
printemps, en re
´ponse a
`la croissance active. Les champignons mycorhiziens a
`arbuscules pourraient e
ˆtre be
´ne
´fiques a
`
E. americanum par l’interme
´diaire d’une absorption mine
´rale moins cou
ˆteuse ou d’une demande en carbone soutenue.
Mots cle
´s:champignons mycorhiziens a
`arbuscules, croissance ve
´ge
´tale, e
´phe
´me
`re de printemps, Erythronium america-
num, nutrition mine
´rale, tempe
´ratures fraı
ˆches.
Introduction
Spring ephemerals are perennial herbaceous species com-
mon in deciduous broad-leaved temperate forests. They have
evolved a characteristic phenology that allows them to take
advantage of the high light intensities, incident on the forest
floor, prior to canopy closure (Lapointe 2001). Growth of
these species is initiated in autumn and is characterized by
the development of new roots and the start of shoot growth.
All growth during autumn and winter occurs underground
and is thus referred to as the hypogeous growth period.
There is no winter dormancy, and shoot growth continues,
albeit at a reduced rate. Following snowmelt, growth accel-
erates, and the shoot rapidly breaks the soil surface. The
subsequent aboveground part of the growth cycle is referred
to as the epigeous growth period and, in most species, flow-
ering occurs during this period (but see Nault and Gagnon
1988). Leaf senescence usually occurs 50–60 d after shoot
emergence. This is followed by fruit maturation and root
senescence, which allows the perennial organ (e.g., bulb,
rhizome, or tuber) to remain dormant during the summer.
The species studied here, Erythronium americanum L., is a
typical bulbous spring ephemeral, very common in sugar
maple stands of Eastern North America.
Received 20 July 2005. Published on the NRC Research Press
Web site at http://canjbot.nrc.ca on 10 March 2006.
L. Lapointe1and S. Lerat.2De
´partement de biologie,
Universite
´Laval, Ste-Foy, QC G1K 7P4, Canada.
1Corresponding author (e-mail: Line.Lapointe@bio.ulaval.ca).
2Present address: De
´partement de biologie, Universite
´de
Sherbrooke, Sherbrooke, QC J1K 2R1, Canada.
39
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The specialized phenology of spring ephemerals requires
a number of adaptations for the plant to perform efficiently.
For example, the root system develops during autumn, when
nutrient needs are restricted by the very slow growth of the
shoot. Therefore, in spring, when nutrient and water require-
ments are much higher, there is a fully developed root sys-
tem to meet these needs. However, this also corresponds to
a time when the root system is, physiologically, relatively
old, and in some species, such as E. americanum, has
stopped growing (Brundrett and Kendrick 1988). Initial
studies have suggested that in spring ephemerals, most nu-
trient absorption occurs during spring (Muller 1978; Ander-
son and Eickmeier 2000). In another spring species,
Hyacinthoides non-scripta, which showed longer leaf life
duration, gain in P also occurs essentially during the epi-
geous growth phase (Merryweather and Fitter 1995).
In autumn, the developing root system of spring ephemer-
als such as E. americanum is rapidly and extensively colon-
ized by arbuscular mycorrhizal (AM) fungi. AM fungi are
known to benefit plants and have been shown to enhance
mineral nutrient uptake, especially P uptake, water absorp-
tion, and resistance to soil pathogens (Smith and Read
1997). In Paris-type AM fungal associations, such as those
formed with E. americanum (Brundrett and Kendrick
1990b), coils are apparently long-lived and might be a site
of nutrient exchange between the host plant and the fungi
(Cavagnaro et al. 2003; Smith et al. 2004). Furthermore, ex-
ternal hyphae, the main site of nutrient absorption (Smith
and Read 1997), could be actively growing in springtime.
In such cases, AM plants could absorb nutrients efficiently,
even if the root system is old and no longer growing such as
in E. americanum in springtime.
Growing through autumn, winter, and early spring re-
quires that spring ephemerals and their AM fungi have the
capacity of absorbing water and nutrients, while soil temper-
atures are low. This becomes more crucial during the epi-
geous growth period, as spring ephemerals exhibit relatively
high photosynthetic rates (Sparling 1967; Taylor and Pearcy
1976) and so require a high water absorption capacity. How-
ever, several studies have shown that water absorption (e.g.,
Markhart et al. 1979) and nutrient uptake (e.g., Marschner
1986) can be restricted at low temperatures, although in
cold-adapted species nutrient uptake capacity appears to ad-
just to match plant growth rate even at low temperature
(Clarkson et al. 1988). While AM fungi might also be able
to overcome this in some way, recent studies have shown
that the growth of many species of AM fungi, as well as
their capacity to absorb P, is reduced at lower temperatures
(Wang et al. 2002; Heinemeyer and Fitter 2004; Liu et al.
2004). Low soil temperature can also influence growth of
the perennial organ, as cell division and cell enlargement
are positively affected by temperature (Francis and Barlow
1988; Pollock and Eagles 1988). As most of the growth
cycle of spring ephemerals occurs during the coldest
months, it is likely that under natural selection pressures
these plant species and their associated AM fungi have
adapted to be less negatively affected by low temperatures
than other temperate species. Indeed, in cultivated bulbous
spring species such as tulip, more biomass is accumulated
during the coolest springs (De Hertogh and Le Nard 1993).
The objectives of the present study were to determine
whether: (i) nutrient absorption occurred mainly during the
epigeous growth phase in E. americanum in both mycorrhi-
zal (M) and nonmycorrhizal (NM) plants, (ii) the growth ca-
pacity of E. americanum was adapted to perform better
under cooler temperatures, and (iii) AM fungi associated
with E. americanum were beneficial to its growth at the
coolest spring temperatures. Mycorrhizal and NM plants of
E. americanum were submitted to different nutrient concen-
trations during the hypogeous (autumn and winter) and epi-
geous (spring) growth periods. Furthermore, the positive
effect of low temperatures on the growth of M and NM
plants was tested during the epigeous growth period by sub-
mitting the plants to two different temperature regimes cor-
responding to the actual understorey temperatures recorded
at the beginning and the end of their natural epigeous
growth.
Materials and methods
Field samples
Specimens of Erythronium americanum L. were collected
near Que
´bec City from a forest that is dominated by Acer
saccharum, with Acer rubrum,Fraxinus americana, and Ul-
mus rubra as companion species. The upper soil horizon
(35 cm) comprises a clay-loam overlain by a thin moder-
type humic horizon. During early spring, the main compo-
nents of the herb layer are E. americanum,Trillium erectum,
and Veratrum viride. Root development of E. americanum
starts in mid-September (L. Lapointe, personal observa-
tions), and these are rapidly colonized by AM fungi (Brun-
drett and Kendrick 1990a; Lapointe and Molard 1997).
Nonmycorrhizal, root-free, vegetative bulbs of
E. americanum (n= 96) were collected in early September
of 1999. These small bulbs are common and usually occur
at a depth of about 5 cm. Mycorrhizal plants (n= 96) were
harvested from the same patches in late October, when all
bulbs had produced new roots. By this time, the NM plants,
which had been submitted to a slow reduction of tempera-
ture (see Hypogeous growth period, below), had also pro-
duced new roots. Fresh biomass (referred to hereafter as
initial biomass) was estimated for both groups of plants. A
subsample of plants (n= 12) was dried (24 h at 70 8C), and
the fresh/dry biomass ratio was calculated to convert initial
biomass to initial dry biomass.
Hypogeous growth period
To simulate field conditions during the hypogeous growth
period, bulbs were potted individually in sterilized 10 cm di-
ameter pots containing Turface1, and the substrate temper-
ature was slowly reduced from 15 8C in early September
for the NM plants, down to 5 8C by the end of November,
under dark conditions, using a growth cabinet (model G30,
Conviron, Winnipeg, Canada). When M plants were potted
at the end of October, the controlled substrate temperature
had reached 8 8C, as did the soil in the field site. From this
point, the two groups of plants followed an identical sub-
strate temperature regime. The substrate was kept moist by
watering with equal amounts of a 1%, 10%, or 50% Hoag-
land’s solution. The 50% Hoagland’s solution contained the
following macronutrients (in mmol×L–1): 5 Ca(NO3)2,
5 KNO3, 1 MgSO4, and 2 KH2PO4, as well as the usual mi-
40 Can. J. Bot. Vol. 84, 2006
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cronutrients found in this solution (Hoagland and Arnon
1950). The 50% Hoagland’s solution was then diluted with
distilled water to provide the 10% and 1% Hoagland’s solu-
tions.
At the end of the hypogeous growth period, marked by
shoot emergence above ground, 12 plants from each treat-
ment (mycorrhizal status Hoagland’s solution concentra-
tion) were harvested and weighed. The roots of four plants
per treatment were used to assess AM fungal colonization
levels (see below), and the bulbs of all plants were dried
(24 h at 70 8C) and weighed. The rest of the plants were
transferred to growth chambers for the epigeous growth pe-
riod (see below).
Epigeous growth period
At the outset of epigeous growth, plants were transferred
to one of two growth cabinets (model E15, Conviron, Win-
nipeg, Canada) with identical 12 h photoperiods but differ-
ent thermal regimes: 12 8C day : 10 8C night or 17 8C day
:158C night. These temperatures were previously deter-
mined after measuring air temperatures, from 21 July 1995
to 7 June 1996, in the experimental field where the
E. americanum bulbs were excavated (unpublished data).
The photon fluence rate at plant level was increased from
100 mmol×m–2×s–1 PAR at the beginning of the photoperiod,
to 360 mmol×m–2×s–1 PAR in the middle of the day (max-
imum maintained for 6 h), and subsequently reduced to 100
mmol×m–2×s–1 PAR towards the end of the photoperiod. The
different fertilization treatments were continued (1%, 10%,
or 50% Hoagland’s nutrient solution) at the rate of one ap-
plication per week. Between fertilizer applications, plants
were watered with tap water as needed. The present experi-
ment was not designed to accurately monitor the exact
amounts of nutrients supplied to plants, but all plants
roughly received the same volumes of nutrient solutions
(1%, 10%, or 50% Hoagland’s).
Total leaf area was calculated at the first sign of senes-
cence, and leaf life span was calculated as the time between
the leaf unfolding and its complete senescence. The plants
were harvested after leaf senescence but before complete
root senescence, weighed, and the roots of four plants per
treatment were used to assess AM colonization levels (see
section below for details). All eight plants were then dried
(24 h at 70 8C) and weighed to obtain the final dry biomass.
As some plants did not sprout, only plants that did produce a
leaf were included in the analysis (n= 5–8). Final/initial dry
biomass ratios were estimated to account for variation in the
initial dry biomass of the plants when harvested the previous
autumn. Bulbs were ground and analysed either for starch or
for nutrient content.
Table 1. Pvalues of two-way ANOVAs performed on final/initial bulb dry biomass, starch con-
centration, and nutrient content of mycorrhizal (M) and nonmycorrhizal (NM) Erythronium ameri-
canum plants at the end of the hypogeous growth period under different nutrient concentrations.
Source of variationa
Variable Mycorrhizal status (Myco.) Fertilization (Fert.) Myco. Fert.
Final/initial bulb biomass <0.001* 0.009* 0.004*b
Starch concentration 0.013* 0.233 0.908
N content 0.173 0.449 0.408
P content 0.108 0.691 0.469
K content 0.180 0.352 0.487
Note: * indicates significant difference at P< 0.05.
adferror = 42 for final/initial bulb biomass and dferror = 11 for starch concentration, and N, P, and K content.
bResults of LSD tests: NM 1% a; NM 10% b; NM 50% b; M 1% c; M 10% c; M 50% c.
0
100
200
300
400
5
00
M1%
M 10%
M 50%
NM 1%
NM 10%
NM 50%
Hypogeous 17/15°C 12/10°C
MNM M MNM NM
(a)
0
1
2
3
4
5
6
(b)
Final/initial bulb biomass Bulb biomass (mg)
Fig. 1. (a) Mean bulb biomass at the end of the hypogeous growth
period and at the end of the epigeous growth period either at
17:15 8C or at 12:10 8C of mycorrhizal (M) and nonmycorrhizal
(NM) Erythronium americanum plants grown under 1%, 10%, or
50% Hoagland’s nutrient solution. (b) Mean final/initial bulb bio-
mass ratio for the hypogeous growth period and the epigeous
growth period either at 17:15 8C or at 12:10 8C for the same treat-
ment groups as in (a). The initial bulb biomass was the estimated
dry biomass at the time of harvest in autumn. Error bars represent
SE, n=8.
Lapointe and Lerat 41
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Analysis of starch content
Two to four bulbs from each treatment harvested at the
end of the hypogeous and epigeous growth periods were an-
alysed for their carbohydrate content. As most of the carbo-
hydrate reserve in E. americanum bulbs occurs as starch
(Lapointe and Molard 1997), only the starch concentration
was estimated. This was done using the method described
by Blakeney and Mutton (1980). Briefly, the ground tissue
was macerated in a mixture (12:5:3 (v/v/v)) of methanol,
chloroform, and water for 20 min at 65 8C and reground using
a Polytron. After centrifugation (5 min at 3500g), the nonsol-
uble residues in the pellet were incubated for 90 min at
100 8C to gelatinize starch and then incubated in the presence
of amyloglucosidase (Sigma Chemical Co., St. Louis, Mis-
souri) for 1 h at 55 8C (Castonguay et al. 1993). The reducing
sugars were measured colorimetrically at 415 nm after reac-
tion with p-hydroxybenzoic acid hydrazide (PAHBAH).
Analysis of N, P, and K content
At the end of the hypogeous and epigeous growth periods,
two to four samples from each treatment were ground and
analysed for N, P, and K. To meet dry mass requirements
for the different analyses, certain treatments required the
pooling of two bulbs. The N (Nkonge and Ballance 1982)
and P (Tandon et al. 1968) concentrations were estimated
colorimetrically following digestion with sulphuric acid, se-
lenic acid, and hydrogen peroxide, while K concentration
was estimated by atomic absorption spectroscopy (model
3300, Perkin-Elmer, Wellesley, Massachusetts). The result-
ing N, P, and K concentrations (mg×g–1) were converted
into total content (mg×bulb–1) by multiplying the concentra-
tion obtained with the dry biomass of each respective bulb.
Mycorrhizal colonization levels
Arbuscular mycorrhizal colonization levels were quanti-
fied at the end of the hypogeous and epigeous growth peri-
ods. Roots were processed according to the technique
outlined in Brundrett et al. (1984), and subsequently cleared
in a 10% (m/v) KOH solution (12 min at 90 8C) before
staining with a 0.05% solution of trypan blue (Phillips and
Hayman 1970). Roots were stored in glycerin prior to as-
sessment of the frequency and intensity of AM colonization
under a microscope (100) using the method described by
Trouvelot et al. (1986). The following parameters were cal-
culated: frequency of colonization, intensity of colonization,
and the arbuscular content of the colonized area (Trouvelot
et al. 1986).
Statistical analysis
Two-way ANOVAs, with mycorrhizal status and the fer-
0
2
4
6
8
0.0
0.2
0.4
0.6
0.8
0
1
2
3
4
5
6
MNM
Hypogeous
Epi
g
eous
12/10°C17/15°C
MMNM NM
(a)
(b)
(c)
K content (mg) P content (mg) N content (mg)
Fig. 3. Mean total mineral content (mg×bulb–1)of(a)N,(b) P, and
(c) K in bulbs at the end of the hypogeous growth period, and at
the end of the epigeous growth period either at 17:15 8Corat
12:10 8C of mycorrhizal (M) and nonmycorrhizal (NM) Erythro-
nium americanum plants grown under 1%, 10%, or 50% Hoag-
land’s nutrient solution. Error bars represent SE, n= 2–4. Legend
as in Fig. 1.
0
200
400
600
800
1000
MNM
Hypogeous 17/15°C 12/10°C
Epi
g
eous
MMNM NM
Starch concentration (mg g )
-1
Fig. 2. Mean bulb starch concentration at the end of the hypogeous
period, and at the end of the epigeous growth period either at
17:15 8C or at 12:10 8C of mycorrhizal (M) and nonmycorrhizal
(NM) Erythronium americanum plants grown under 1%, 10%, or
50% Hoagland’s nutrient solution. Error bars represent SE, n= 2–4.
Legend as in Fig. 1.
42 Can. J. Bot. Vol. 84, 2006
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tilization regime as the main factors, were used to compare
bulb nutrient total content (mg×bulb–1), bulb starch concen-
tration, and final/initial dry biomass at the end of the hypo-
geous growth period. A one-way ANOVA, with the
fertilization regime as the main factor, was used to compare
AM fungal colonization levels in M plants, as roots of NM
plants were never colonized by AM fungi (data not shown).
Three-way ANOVAs, with mycorrhizal status, the fertil-
ization regime, and temperature as the main factors, were
used to compare bulb nutrient concentration and total con-
tent, leaf area, leaf life span, changes in bulb dry biomass,
and final bulb starch concentrations at the end of the epi-
geous growth period. Two-way ANOVAs, with the fertiliza-
tion regime and temperature as main factors, were used to
compare AM fungal colonization levels at the end of the
epigeous growth period. When either two-way or three-way
ANOVA tests showed statistical differences for the fertiliza-
tion regime or for any of the two-factor interactions, a pos-
teriori LSD tests were performed. Differences observed with
these LSD tests are presented as different letters following
treatment names (see notes below Tables 1–3).
Results
Hypogeous growth period
At the end of the hypogeous growth period, the bulb of
NM plants exhibited a lower dry biomass and a lower starch
concentration compared with their M counterparts (Table 1;
Figs. 1 and 2). Bulbs of NM plants receiving 1% Hoagland’s
solution had a lower dry biomass than plants receiving 10%
or 50% solutions (Table 1; Fig. 1). Nutrient concentrations
(mg×g–1 dry biomass; data not shown; P> 0.28) and total
content (mg×bulb–1) were similar for M and NM plants and
for the different fertilization regimes (Table 1; Fig. 3).
Epigeous growth period
As starch concentration in the bulbs was high and varied
between treatments (see below), we tested for its impact on
nutrient concentration. There were strong negative Spearman
correlations (P< 0.001) between starch concentration and
the concentrations of N, P, and K in the bulbs. To eliminate
the dilution effect induced by starch content, bulb nutrient
concentrations were calculated as a function of the bulb dry
biomass minus its starch content. There was a significant in-
teraction between fertilization and temperature on both final
N and K concentrations, but there were no clear patterns
(Table 2). The treatments had no effect on final P concentra-
tion in the bulbs (P= 0.07). However, global gains in N, P,
and K were observed between the end of the hypogeous and
the end of the epigeous growth period for all treatment
groups (Fig. 3). Significant differences between treatments
in the final nutrient content of the bulbs were observed.
Bulb N, P, and K contents increased with mineral fertiliza-
tion and were positively influenced by the lower temperature
regime (Table 2; Fig. 3).
Low temperatures increased leaf life span, leaf area,
change in bulb biomass, and final starch concentration of
the bulb (Table 3; Figs. 1, 2, 4). The presence of AM fungi
had a negative effect on leaf life span at the lower temper-
ature regime (Fig. 4), but had a positive effect on the change
in bulb biomass and final bulb biomass under both temper-
ature regimes (Fig. 1). Changes in bulb biomass and the fi-
nal starch concentration were affected by the different
fertilization treatments (Table 3). Final starch concentration
decreased with increasing concentrations of fertilizers
(Fig. 2). Changes in bulb biomass of M plants were smaller
at the highest fertilization treatment, while bulb biomass of
NM plants remained relatively constant at all fertilization
treatments (Fig. 1b). The mycorrhizal fertilization interac-
tion was indeed nearly significant (P= 0.055, Table 3).
Mycorrhizal colonization levels
Roots of NM plants were devoid of AM fungal structures.
In M plants, during the hypogeous growth period, there was
no effect of the different fertilization levels on the frequency
(P= 0.70; dferror = 9) or intensity (P= 0.66; dferror = 9; Ta-
ble 4) of AM fungal colonization. During the epigeous
Table 2. Pvalues of three-way ANOVAs performed on bulb nutrient concentrations (expressed as
bulb dry biomass – bulb starch content) and the N, P, and K bulb contents at the end of the epigeous
growth period of mycorrhizal and nonmycorrhizal Erythronium americanum plants grown under dif-
ferent temperature and fertilization treatments.
Nutrient concentration Nutrient content
Source of variationaNP
bKN P K
Mycorrhizal status (Myco.) 0.192 0.072 0.424 0.920 0.677 0.792
Fertilization (Fert.) 0.003* 0.877 0.603 <0.001*c0.004*c0.002*c
Temperature (Temp.) 0.079 0.198 0.032* <0.001* 0.047* <0.001*
Myco. Fert. 0.177 0.110 0.339 0.420 0.552 0.351
Myco. Temp. 0.241 0.877 0.687 0.800 0.532 0.510
Fert. Temp. 0.037*d0.120 0.003*e0.052 0.129 0.264
Myco. Fert. Temp. 0.478 0.761 0.436 0.858 0.969 0.700
Note: * indicates significant difference at P< 0.05.
adferror = 27.
bData were log transformed.
cResults of LSD tests: 50% a; 10% a; 1% b.
dResults of LSD tests: 17:15 8C 1% had significantly lower N concentration than all other groups. There were no
other significant differences.
eResults of LSD tests: 12:10 8C 1% a; 12:10 8C 10% ab; 17:15 8C 50% ab; 17:15 8C 10% b; 12:10 8C 50% bc;
17:15 8C1%c.
Lapointe and Lerat 43
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growth period, only temperature had an effect on the intensity
of colonization (P= 0.03; data rank-transformed; dferror = 18),
with a higher intensity occurring under the higher tempera-
ture regime.
Discussion
There was no net nutrient gain between the beginning and
the end of the hypogeous growth period in either M or NM
plants as shown by the lack of fertilization impact on bulb
nutrient content. These results confirm that there is little nu-
trient absorption in E. americanum during the hypogeous
growth period (autumn and winter), but rather during spring
(Muller 1978). Similar results have been observed with
Claytonia virginica, another North American spring ephem-
eral (Anderson and Eickmeier 2000), and with Hyacin-
thoides non-scripta (Merryweather and Fitter 1995). It is
possible that E. americanum roots also accumulate nutrients
during winter, but as bulbs were harvested at the outset of
epigeous growth, translocation of nutrients from the roots or
AM structures to the shoot should have already occurred.
Since roots senesce shortly after complete shoot senescen-
cence in early summer, we can conclude that spring appears
to be the main active period for nutrient absorption in
E. americanum.
At the end of the epigeous period, the nutrient content of
the bulbs was globally higher at the two highest fertilization
rates (10% and 50% Hoagland’s nutrient solution). How-
ever, the general pattern was not different between these
two fertilization rates. This probably indicates that the nu-
trient uptake capacity of E. americanum is reached using
the 10% Hoagland’s nutrient solution, and that further nu-
trient supply has no significantly positive impact on nutrient
absorption. Although spring ephemerals are considered as
species flourishing in rich forest soils (Rogers 1982), the
present results are consistent with the study of Rothstein
and Zak (2001) where the spring ephemeral
Allium tricoccum exhibited a lower N uptake capacity than
that of two co-occurring forest herbs, the summergreen Vi-
ola pubescens and the semi-evergreen Tiarella cordifolia.It
might thus be typical of spring ephemerals to show low nu-
trient absorption capacity, because of their coarse root sys-
tem (Newsham et al. 2004). While they require rich soils to
absorb sufficient nutrient to support growth, when fertilized,
Table 3. Pvalues of three-way ANOVAs performed on leaf life span, leaf area, final/initial dry
biomass, and bulb starch concentration at the end of the epigeous growth period of mycorrhizal (M)
and nonmycorrhizal (NM) Erythronium americanum plants grown under different temperature and
fertilization treatments.
Source of variationaLeaf life spanbLeaf areac
Final/initial bulb
dry biomass
Bulb starch
concentration
Mycorrhizal status (Myco.) 0.221 0.656 0.009* 0.232
Fertilization (Fert.) 0.456 0.169 0.030*d<0.001*e
Temperature (Temp.) <0.001* 0.010* <0.001* <0.001*
Myco. Fert. 0.249 0.140 0.055 0.474
Myco. Temp. <0.001*f0.537 0.827 0.863
Fert. Temp. 0.246 0.421 0.845 0.056
Myco. Fert. Temp. 0.469 0.248 0.624 0.992
Note: * indicates significant difference at P< 0.05.
adferror = 75 for leaf area, leaf life span, and final/initial bulb dry biomass, dferror = 28 for bulb starch
concentration.
bData are rank transformed.
cData are square root transformed.
dResults of LSD tests: 10% a; 1% a; 50% b.
eResults of LSD tests: 1% a; 10% b; 50% c.
fResults of LSD tests: 12:10 8C NM a; 12:10 8C M b; 17:15 8C M bc; 17:15 8CNMc.
Leaf life span (d)
0
10
20
30
40
50
60
70
MNM MNM
Leaf area (cm2)
0
2
4
6
8
(a)
(b)
Fig. 4. Mean (a) leaf life span and (b) leaf area for the epigeous
growth period either at 17:15 8C or at 12:10 8C of mycorrhizal (M)
and nonmycorrhizal (NM) Erythronium americanum plants grown
under 1%, 10%, or 50% Hoagland’s solution. Error bars represent
SE, n= 5–8. Legend as in Fig. 1.
44 Can. J. Bot. Vol. 84, 2006
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their nutrient uptake mechanisms or their capacity to store
nutrients becomes rapidly saturated. This would explain
why bulb growth did not benefit from the highest mineral
fertilization. The apparent good growth at the lowest fertil-
ization rate seems to be due to a higher starch concentration,
as nutrient content was negatively correlated with bulb
starch concentration. Therefore, plant biomass itself, in such
species, does not always reflect good growing conditions.
Arbuscular mycorrhizal fungi had no net impact on nu-
trient content. Nevertheless, the presence of AM fungi had
a positive impact on bulb biomass at the two lower fertiliza-
tion rates (1% and 10% Hoagland’s nutrient solution).
Although M plants showed slightly larger biomass at the
end of the hypogeous growth period than NM plants
(Fig. 1), this cannot fully explain the much larger differen-
ces observed between M and NM plants at the end of the
epigeous growth phase. When E. americanum M plants are
of similar biomass as fungicide-treated plants at the end of
the hypogeous growth period, they still reach a higher final
biomass than fungicide-treated plants (Lapointe and Molard
1997). Other studies have also reported an AM impact on
plant biomass without increased P content (Pearson and Ja-
kobsen 1993). We cannot rule out the possibility that the ex-
tra-radical hyphal network was not fully restored after
autumn harvesting of M plants in the field (Boddington and
Dodd 2000), leading to a reduction of the impact of AM
symbiosis on mineral nutrition in the present study. Never-
theless, it has recently been demonstrated that AM fungi
can contribute to a large percentage of P uptake, even in
species where M plants exhibit similar biomass and P con-
tent as NM plants (Smith et al. 2004). In E. americanum,it
might be less costly to absorb nutrients via the mycorrhizal
pathway than via its own root epidermal cells, especially
when nutrients are in low concentration in the soil. How-
ever, it seems that E. americanum is less dependant upon
AM fungi for its mineral nutrition than Hyacinthoides non-
scripta, which showed an overall reduction in P content in
NM or fungicide-treated plants compared with M plants
(Merryweather and Fitter 1995, 1996).
The present study revealed that, at the outset of the epi-
geous growth period, the bulb biomass and starch concentra-
tions were higher in M than in NM plants. This is in
contrast with a previous study where M and fungicide-
treated E. americanum plants showed similar biomass at the
end of the hypogeous growth periods, and M bulbs showed
lower starch concentrations than fungicide-treated bulbs (La-
pointe and Molard 1997). This may be due to the fact that
the AM fungal colonization levels observed in the present
experiment were much lower than have been reported in
other studies (Brundrett and Kendrick 1990b; Lapointe and
Molard 1997; Lerat et al. 2002). As the capacity of AM
fungi to drain carbohydrates has been shown to be closely
correlated to M levels (Thomson et al. 1990; Lerat et al.
2003), the production of longer roots in NM plants in the
present experiment (data not shown, P< 0.001) appears to
be more expensive, in terms of carbohydrate utilization,
than maintaining AM fungi at low colonization levels. How-
ever, we cannot exclude the possibility that the different
growing conditions of M and NM plants between early Sep-
tember and late October also influenced bulb carbohydrate
content during the hypogeous growth period.
The positive AM effect on final plant biomass was ob-
served at both temperature regimes; this suggests that AM
fungal species associated with E. americanum are capable
of absorbing nutrients efficiently at low temperatures. Stud-
ies that have shown reduced AM fungi growth at lower tem-
peratures have been conducted with different AM fungal
species (Glomus intraradices (Wang et al. 2002; Liu et al.
2004), or Glomus mosseae,Glomus hoi, and Acaulospora
sp. (Heinemeyer and Fitter 2004)) suggesting that this re-
sponse might be common amongst AM fungal species.
There appears to be a reduction in AM colonization at the
lower temperature regime and extra-radical mycelium
growth might have been reduced as well as shown in vitro
with a transformed root system (Liu et al. 2004) and in a
growth chamber study (Tommerup 1983). Although it is
possible that P absorption in AM fungi associated with
E. americanum is reduced at low temperature, as observed
in Allium porrum colonized with Glomus intraradices
(Wang et al. 2002), it did not translate at the end of the sea-
son into a reduction of P content. Arbuscular mycorrhizal
fungi associated with E. americanum roots might be able to
satisfy the plant nutrient needs, even when nutrient absorp-
tion is slowed down, because of the overall low growth rate
of the plant species.
Arbuscular mycorrhizal fungi might influence growth of
E. americanum through other means than mineral nutrition
alone. The maintenance of a sustained carbon sink through-
Table 4. Frequency and intensity of arbuscular mycorrhizal fungal colonization (% ± SE) of Erythronium
americanum roots at the end of the hypogeous and epigeous growth periods under different fertilization and
temperature (epigeous period only) treatments (n= 4).
Growth period
Temperature regime
(8C, day:night)
Fertilization treatment
(Hoagland’s)
Frequency of
colonization (%)
Intensity of
colonization (%)
Hypogeous period Cold treatment 1% 17.2±6.8 1.5±1.0
10% 19.2±9.8 2.7±2.2
50% 27.0±8.8 3.7±3.2
Epigeous period 12:10 1% 19.7±10.6 0.65±0.46
17:15 22.3±4.9 0.81±0.25
12:10 10% 6.9±2.0 0.10±0.04
17:15 20.5±12.9 1.47±0.77
12:10 50% 8.3±5.2 0.19±0.14
17:15 26.8±10.0 1.05±0.43
Lapointe and Lerat 45
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out the season (Wright et al. 1998) might favour higher pho-
tosynthetic rates, which in return would result in greater
bulb biomass at the end of the season, as shown by Louche-
Tessandier et al. (1999) in potato plants. Either through the
maintenance of an elevated photosynthetic rate or through a
less costly water and nutrition uptake system, AM symbiosis
is likely to be beneficial for the growth of E. americanum in
the understorey, at least based on the results published so far.
The cooler temperature regime during the epigeous
growth period (12 8C:108C) had a strong positive effect
on E. americanum final bulb size. However, the experimen-
tal design did not allow to test the impact of temperature in-
dependently of the growth chamber effect owing to the fact
that there was a single chamber per temperature treatment.
Since this study was conducted, we have grown spring
ephemerals at both cool and warmer growth temperatures,
in different growth chambers, and repeatedly obtained larger
final size at the cooler temperature regime. Two species
were tested so far, Erythronium americanum (F. Baptist, un-
published data; S. Gutjahr, unpublished data) and Crocus
vernus (L.) Hill (Badri 2003; L. Lapointe, unpublished
data). Erythronium americanum was expected to grow well
at low temperatures, as the natural growth period of this
plant corresponds with the time of year when air and soil
temperatures are at their coolest. However, examples of
plant species with optimal growth rates at cool instead of
warm temperatures are rare in the literature. To date, such
responses have only been observed in plants that naturally
grow under some of the most severe climatic conditions.
Studies realized on the high-arctic alpine grass Phippsia
algida and on the high-arctic plant Koenigia islandica re-
ported optimal dry matter productivity at temperatures of
98C (Heide 1992) and 12 8C (Heide and Gauslaa 1999), re-
spectively. The spring ephemeral Floerkea proserpina-
coides, an annual species that occurs in similar habitats as
E. americanum, has lower plant biomass at cooler tempera-
tures (McKenna and Houle 2000). Therefore, E. americanum
is, to the best of our knowledge, the first case of a plant spe-
cies from a temperate region that would have a cool temper-
ature growth optimum.
The mechanisms underlying enhanced growth at low tem-
peratures seem complex, as they appear to be linked to leaf
life span, final leaf area, and starch accumulation. The final
leaf area is probably related to leaf life span, as the leaf of
E. americanum, such as other spring ephemerals (Zubkova
et al. 1997), grows continuously after emergence
(L. Lapointe, personal observation). In E. americanum, low
temperatures lengthen the period of photosynthetic activity,
which could likely result in a larger bulb and greater starch
accumulation. However, leaf life span alone cannot explain
improved growth under the lower temperature regime, be-
cause M plants showed greater biomass despite shorter leaf
life span than NM plants. The influence of temperature on
the intrinsic growth rate of the bulb might explain part of
the increase in final biomass at the lower temperature. A
similar situation has been recently observed in Crocus ver-
nus, an ornamental species with a short leaf life span (Badri
2003). Further studies are underway to unravel the mecha-
nisms allowing such species to show high biomass accumu-
lation at low temperatures.
In summary, the present study confirmed that nutrient up-
take in E. americanum mainly occurs during spring. Both
roots and AM fungi were capable of maintaining sufficient
nutrient uptake at lower temperatures to keep up with the
growth rate of the bulb. Although AM presence did not
translate into higher nutrient uptake, M plants showed higher
final biomass than NM plants. Nutrient absorption through
AM symbiosis might be less expensive in terms of carbohy-
drate use than through direct absorption by epidermal cells.
Arbuscular mycorrhizal symbiosis might also stimulate plant
growth by maintaining a constant sink throughout the epi-
geous growth period. But the most remarkable result was
the difference in bulb size between the cool- and warmer-
grown plants. To our knowledge, this increase in plant bio-
mass at lower temperature has not been reported in another
temperate species. However, the metabolic traits underlying
the capacity of E. americanum to grow better at low temper-
atures deserves further examination.
Acknowledgements
The authors thank Marie-Claude Routhier, Simon Bou-
dreault, and Pierre Cordeau for their help in gathering the
data, and Andrew P. Coughlan for the revision of this text.
This study was supported by a research grant from the Nat-
ural Sciences and Engineering Research Council of Canada
(NSERC) to Line Lapointe.
References
Anderson, W.B., and Eickmeier, W.G. 2000. Nutrient resorption in
Claytonia virginica L.: implications for deciduous forest nutrient
cycling. Can. J. Bot. 78: 832–839. doi: 10.1139/cjb-78-6-832.
Badri, M.A. 2003. Effets de la tempe
´rature sur la croissance de la
plante bulbeuse a
`floraison printanie
`re: Crocus vernus (L.) Hill.
M.Sc. thesis, De
´partement de biologie, Universite
´Laval, Que
´-
bec, Que
´.
Blakeney, A.B., and Mutton, L.L. 1980. A simple colorimetric
method for the determination of sugars in fruit and vegetables.
J. Sci. Food Agric. 31: 889–897.
Boddington, C.L., and Dodd, J.C. 2000. The effect of agricultural
practices on the development of indigenous arbuscular mycorrhi-
zal fungi. I. Field studies in an Indonesian ultisol. Plant Soil,
218: 137–144. doi: 10.1023/A:1014966801446.
Brundrett, M.C., and Kendrick, B. 1988. The mycorrhizal status,
root anatomy, and phenology of plants in a sugar maple forest.
Can. J. Bot. 66: 1153–1173.
Brundrett, M.C., and Kendrick, B. 1990a. The roots and mycorrhi-
zas of herbaceous woodland plants. I- Quantitative aspects of
morphology. New Phytol. 114: 457–468.
Brundrett, M.C., and Kendrick, B. 1990b. The roots and mycorrhi-
zas of herbaceous woodland plants. II- Structural aspects of
morphology. New Phytol. 114: 469–479.
Brundrett, M., Piche
´, Y., and Peterson, R.L. 1984. A new method
for observing the morphology of vesicular-arbuscular mycorrhi-
zae. Can. J. Bot. 62: 2128–2134.
Castonguay, Y., Nadeau, P., and Simard, R.R. 1993. Effects of
flooding on carbohydrate and ABA levels in roots and shoots of
alfalfa. Plant Cell Environ. 16: 695–702.
Cavagnaro, T.R., Smith, F.A., Ayling, S.M., and Smith, S.E. 2003.
Growth and phosphorus nutrition of a Paris-type arbuscular my-
corrhizal symbiosis. New Phytol. 157: 127–134. doi: 10.1046/j.
1469-8137.2003.00654.x.
Clarkson, D.T., Earnshaw, M.J., White, J., and Cooper, H.D. 1988.
Temperature dependent factors influencing nutrient uptake - An
46 Can. J. Bot. Vol. 84, 2006
#2006 NRC Canada
Can. J. Bot. Downloaded from www.nrcresearchpress.com by Depository Services Program on 05/28/13
For personal use only.
analysis of responses at different levels of organization. In
Plants and temperature. Edited by S.P. Long and
F.I. Woodward. The Company of Biologists Limited, Cam-
bridge, UK. pp. 281–309.
De Hertogh, A., and Le Nard, M. 1993. The physiology of flower
bulbs. A comprehensive treatise on the physiology and utiliza-
tion of ornamental flowering bulbous and tuberous plants. Else-
vier, Amsterdam, Netherlands.
Francis, D., and Barlow, W. 1988. Temperature and the cell cycle.
In Plants and temperature. Edited by S.P. Long and
F.I. Woodward. The Company of Biologists Limited, Cam-
bridge, UK. pp. 181–201.
Heide, O.M. 1992. Flowering strategies of the high-arctic and high-
alpine snow bed grass species Phippsia algida. Physiol. Plant.
85: 606–610. doi: 10.1034/j.1399-3054.1992.850407.x.
Heide, O.M., and Gauslaa, Y. 1999. Developmental strategies of
Koenigia islandica, a high-arctic annual plant. Ecography, 22:
637–642.
Heinemeyer, A., and Fi tter, A.H. 2004. Impact of temperature on
the arbuscular mycorrhizal (AM) symbiosis: growth responses of
the host plant and its AM fungal partner. J. Exp. Bot. 55: 525–
534. doi: 10.1093/jxb/erh049. PMID: 14739273.
Hoagland, D.R., and Arnon, D.I. 1950. The water culture method
for growing plants without soil. California Agricultural Experi-
ment(al) Station Circular No. 347. pp. 1–32.
Lapointe, L. 2001. How phenology influences physiology in decid-
uous forest spring ephemerals. Physiol. Plant. 113: 151–157.
doi: 10.1034/j.1399-3054.2001.1130201.x. PMID: 12060291.
Lapointe, L., and Molard, J. 1997. Costs and benefits of mycorrhi-
zal infection in a spring ephemeral, Erythronium americanum.
New Phytol. 135: 491–500. doi: 10.1046/j.1469-8137.1997.
00672.x.
Lerat, S., Gauci, R., Catford, J.G., Vierheilig, H., Piche
´, Y., and
Lapointe, L. 2002. 14C transfer between the spring ephemeral
Erythronium americanum and sugar maple saplings via arbuscu-
lar mycorrhizal fungi in natural stands. Oecologia, 132: 181–
187. doi: 10.1007/s00442-002-0958-9.
Lerat, S., Lapointe, L., Gutjahr, S., Piche
´, Y., and Vierheilig, H.
2003. Carbon partitioning in a split-root system of arbuscular
mycorrhizal plants is fungal and plant species dependent. New
Phytol. 157: 589–595. doi: 10.1046/j.1469-8137.2003.00691.x.
Liu, A., Wang, B., and Hamel, C. 2004. Arbuscular mycorrhiza co-
lonization and development at suboptimal root zone temperature.
Mycorrhiza, 14: 93–101. doi: 10.1007/s00572-003-0242-9.
PMID: 12748840.
Louche-Tessandier, D., Samson, G., Herna
´ndez-Sebastia
´, C., Chag-
vardieff, P., and Desjardins, Y. 1999. Importance of light and
CO2on the effects of endomycorrhizal colonization on growth
and photosynthesis of potato plantlets (Solanum tuberosum)in
an in vitro tripartite system. New Phytol. 142: 539–550. doi:
10.1046/j.1469-8137.1999.00408.x.
Markhart, A.H., III, Fiscus, E.L., Naylor, A.W., and Kramer, P.J.
1979. Effect of temperature on water and ion transport in soy-
bean and broccoli systems. Plant Physiol. 64: 83–87.
Marschner, H. 1986. Mineral nutrition of higher plants. Academic
Press, London, Tokyo.
McKenna, M.F., and Houle, G. 2000. Why are annual plants rarely
spring ephemerals? New Phytol. 148: 295–302. doi: 10.1046/j.
1469-8137.2000.00756.x.
Merryweather, J., and Fitter, A.H. 1995. Phosphorus and carbon
budgets: mycorrhizal contribution in Hyacinthoides non-scripta
(L.) Chouard ex Rothm. under natural conditions. New Phytol.
129: 619–627.
Merryweather, J., and Fitter, A.H. 1996. Phosphorus nutrition of an
obligately mycorrhizal plant treated with the fungicide benomyl
in the field. New Phytol. 132: 307–311.
Muller, R.N. 1978. The phenology, growth and ecosystem dy-
namics of Erythronium americanum in the northern hardwood
forest. Ecol. Monogr. 48: 1–20.
Nault, A., and Gagnon, D. 1988. Seasonal biomass and nutrient al-
location patterns in wild leek (Allium tricoccum Ait.), a spring
geophyte. Bull. Torrey Bot. Club, 115: 45–54.
Newsham, K.K., Fitter, A.H., and Watkinson, A.R. 2004. Multi-
functionality and biodiversity in arbuscular mycorrhizas. Trends
Ecol. Evol. 10: 407–411.
Nkonge, C., and Ballance, G.M. 1982. A sensitive colorimetric pro-
cedure for nitrogen determination in micro-Kjeldahl digests. J.
Agric. Food Chem. 30: 416–420. doi: 10.1021/jf00111a002.
Pearson, J.N., and Jakobsen, I. 1993. The relative contribution of
hyphae and roots to phosphorus uptake by arbuscular mycorrhi-
zal plants, measured by dual labelling with 32P and 33P. New
Phytol. 124: 489–494.
Phillips, J.M., and Hayman, D.S. 1970. Improved procedures for
clearing roots and staining parasitic and vesicular-arbuscular
mycorrhizal fungi for rapid assessment of infection. Trans. Br.
Mycol. Soc. 55: 158–161.
Pollock, C.J., and Eagles, C.F. 1988. Low temperature and the
growth of plants. In Plants and temperature. Edited by
S.P. Long and F.I. Woodward. The Company of Biologists Lim-
ited, Cambridge, UK. pp. 157–180.
Rogers, R.S. 1982. Early spring herb communities in mesophytic
forests of the Great Lakes region. Ecology, 63: 1050–1063.
Rothstein, D.E., and Zak, D.R. 2001. Relationships between plant
nitrogen economy and life history in three deciduous-forest
herbs. J. Ecol. 89: 385–394. doi: 10.1046/j.1365-2745.2001.
00555.x.
Smith, S.E., and Read, D.J. 1997. Mycorrhizal symbiosis, 2nd ed.
Academic Press, San Diego, California.
Smith, S.E., Smith, F.A., and Jakobsen, I. 2004. Functional diver-
sity in arbuscular mycorrhizal (AM) symbioses: the contribution
of the mycorrhizal P uptake pathway is not correlated with my-
corrhizal responses in growth or total P uptake. New Phytol.
162: 511–524. doi: 10.1111/j.1469-8137.2004.01039.x.
Sparling, J.H. 1967. Assimilation rates of some woodland herbs in
Ontario. Bot. Gaz. 128: 160–168. doi: 10.1086/336393.
Tandon, H.L.S., Cescas, M.P., and Tyner, E.H. 1968. An acid-free
vanadate-molybdate reagent for the determination of total phos-
phorus in soils. Soil Sci. Soc. Am. Proc. 32: 48–51.
Taylor, R.J., and Pearcy, R.W. 1976. Seasonal patterns of the CO2
exchange characteristics of understory plants from a deciduous
forest. Can. J. Bot. 54: 1094–1103.
Thomson, B.D., Robson, A.D., and Abbott, L.K. 1990. Mycorrhizas
formed by Gigaspora calospora and Glomus fasciculatum on
subterranean clover in relation to soluble carbohydrate concen-
trations in roots. New Phytol. 114: 217–225.
Tommerup, I.C. 1983. Temperature relations of spore germination
and hyphal growth of vesicular-arbuscular mycorrhizal fungi in
soil. Trans. Br. Mycol. Soc. 81: 381–387.
Trouvelot, A., Kough, J.L., and Gianinazzi-Pearson, V. 1986. Me-
sure du taux de mycorhization VA d’un syste
`me radiculaire. Re-
cherche de me
´thodes d’estimation ayant une signification
fonctionnelle. In Physiological and genetical aspects of mycor-
rhizae. Institut national de la recherche agronomique (INRA)
Publications, Paris. pp. 217–221.
Wang, B., Funakoshi, D.M., Dalpe
´, Y., and Hamel, C. 2002. Phos-
phorus-32 absorption and translocation to host plants by arbus-
cular mycorrhizal fungi at low root-zone temperature.
Mycorrhiza, 12: 93–96. PMID: 12035733.
Lapointe and Lerat 47
#2006 NRC Canada
Can. J. Bot. Downloaded from www.nrcresearchpress.com by Depository Services Program on 05/28/13
For personal use only.
Wright, D.P., Read, D.J., and Scholes, J.D. 1998. Mycorrhizal sink
strength influences whole plant carbon balance of Trifolium re-
pens L. Plant Cell Environ. 21: 881–891. doi: 10.1046/j.1365-
3040.1998.00351.x.
Zubkova, E.K., Mamushina, N.S., Voitsekhovskaya, O.V., and Fi-
lippova, L.A. 1997. Respiratory metabolism of monocot ephe-
mers under photosynthetic conditions in light. Russ. J. Plant
Physiol. 44: 158–165.
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  • ... day/night and relative humidity at 65% during the whole epigeous growth period. Plants were watered daily and fertilized weekly with 10% Hoagland's solution for optimal growth ( Lapointe and Lerat, 2006). ...
    Thesis
    Les relations entre l'activité de la source et l'activité du puits contrôlent en grande partie la croissance des plantes. Ces activités varient au cours du développement, mais aussi en réponse à des changements des conditions environnementales. Notre étude avait pour but d'identifier le rôle du métabolisme carboné dans la réponse de la croissance d'E. americanum à la modulation des activités de la source et du puits. Dans une première partie, l'activité du puits est modulée par la température de croissance. Aux fortes températures, l'activité du puits est plus élevée, alors que sa capacité est réduite. Ces effets, dus à la modulation du métabolisme du saccharose, mènent à une saturation précoce en amidon des bulbes à forte température. Par la suite, la baisse de la demande en carbone du puits induit un rétrocontrôle négatif de l'activité photosynthétique et finalement, la sénescence foliaire. À l'inverse, l'activité du puits à faible température est en rythme avec l'accroissement de la capacité, menant à une biomasse supérieure du bulbe en fin de croissance épigée. Dans une seconde partie, l'activité de la source est modulée en changeant la concentration en CO2 et en O3. Malgré la stimulation de la source sous fort CO2 et son inhibition sous fort O3, l'accumulation d'amidon et la biomasse du bulbe ne sont pas affectées. En effet, le surplus de carbone parvenant au puits est brûlé par la voie alternative de la respiration, celle-ci étant stimulée par l'activité de l'enzyme malique. La voie alternative de la respiration évite ainsi une saturation hâtive en amidon et éventuellement, une sénescence foliaire précoce. Dans une dernière partie, l'activité de la source est modulée par l'irradiance et la photopériode. L'accumulation d'amidon varie en fonction de la photopériode alors que l'irradiance n'a aucun effet. De plus, l'activité photosynthétique est inhibée très précocement sous longue photopériode. Cette inhibition semble due à un déséquilibre entre la quantité totale de carbone fixé par jour et son utilisation suite à son transfert au sein du bulbe. Nous pouvons donc conclure que les régulations du métabolisme carboné permettent d'ajuster l'activité du puits à la capacité de celui-ci chez l'E. americanum.
  • ... Ambient air in each chamber was analysed continuously by an ozone analyser (O341M, Environment SA, Paris, France) and a CO 2 analyser (WMA2 PPsystems, Stotfold, UK). Plants were watered daily and fertilized weekly with 10% Hoagland's solution to ensure optimal growth ( Lapointe and Lerat, 2006). ...
  • ... The natural timing of senescence prior to canopy closure occurs after carbohydrate reserves have been stored in perennating organs (Risser & Cottam 1968;Lapointe 2001) and prevents loss of leaf carbo- hydrates in response to high respiration at high temperatures in these shade-intolerant species. Leaf senescence of some spring ephemerals accelerates with warmer spring tempera- tures in constant shade (Yoshie & Fukuda 1994;Lapointe & Lerat 2006), but also occurs for some species under constant high-light conditions (Risser & Cottam 1967;Yoshie & Fukuda 1994; C. Augspurger, unpubl. data), indicating that shading is not the only factor affecting senescence (Lapointe 2001). ...
    Article
    Spring ephemeral herb species in temperate deciduous forests are active aboveground only briefly each year. This study tested experimentally how two countervailing constraints – cold and darkness – influence the phenology of six spring herb species. 2.Dormancy of underground structures, maintained by cold temperatures in a growth chamber, was broken at six 25-day intervals from January or February to June in two consecutive years. Upon emergence, survival and flowering were measured on cohorts grown outdoors. Shade cloth was added at the time of normal canopy closure. 3.Cardamine concatenata, Dicentra cucullaria, Erythronium albidum, and Trillium recurvatum had no or low 2-yr survival in the two or three earliest cohorts and no or low survival in the latest cohort, relative to their natural cohort. Allium canadense and Claytonia virginica had survival in all cohorts. Flowering never occurred in the first two or three cohorts for three species and never occurred or declined in later cohorts in all species. 4.Despite widely differing emergence dates, senescence was completed within a 40-day period soon after shade was imposed for all cohorts for all species. Consequently, leaf lifespan became shorter as date of emergence was delayed among cohorts. 5.In general, the brief growth period of spring herb species is an adaptation to avoid winter cold and late spring canopy shade. These constraints are species-specific and differ for survival and flowering for some species. Claytonia virginica is the most tolerant among the species to a wider range of conditions. 6.Synthesis. Knowing that cold and shade constrain a plant's non-dormant period is important because of the significant role plant phenology plays in responses to climate change. This article is protected by copyright. All rights reserved.
  • Article
    Many spring geophytes exhibit greater growth at colder than at warmer temperatures. Previous studies have suggested that there is less disequilibrium between source and sink activity at low temperatures, which delays leaf senescence and leads to higher accumulation of biomass in the perennial organ. We hypothesized that dark respiration acclimates to temperature at both the leaf and bulb levels, mainly via the alternative respiratory pathway, as a way to reduce source-sink imbalance. Erythronium americanum Ker-Gawl. was grown under three temperature regimes: 8/6 °C, 12/8 °C, and 18/14 °C (day/night). Plant respiratory rates were measured at both growth and common temperatures to determine whether differences were due to the direct effects of temperature on respiratory rates or to acclimation. Leaf dark respiration exhibited homeostasis, which together with lower assimilation at low growth temperature, most likely reduced the quantity of C available for translocation to the bulb. No temperature acclimation was visible at the sink level. However, bulb total respiration varied through time, suggesting potential stimulation of bulb respiration as sink limitation builds up. In conclusion, acclimation of respiration at the leaf level could partly explain the better equilibrium between source and sink activity in plants grown in low-temperatures, whereas bulb respiration responds to source-sink imbalance.
  • Article
    Alyssum desertorum (Alysseae, Brassicaceae) is an annual spring ephemeral plant whose life cycle is only 2-3 months. It typically has high photosynthetic capacity and a high growth rate. However, little is known about the chloroplast (cp) genome structure of this species. Furthermore, the phylogenetic position of the tribe Alysseae relative to other tribes in the Brassicaceae has not been determined due to inconsistences in different DNA markers. This study is the first report on a cp genome of the genus Alyssum and discusses the phylogenetic relationships of the tribe Alysseae relative to other tribes in the family. The complete cp genome of A. desertorum was 151,677 bp in size and is the smallest cp genome in the Brassicaceae sequenced to date. The genome includes a large single-copy region of 81,551 bp, a small single-copy region of 17,804 bp, and two inverted repeats of 26,161 bp each. The genome contains 132 genes, including 86 protein-coding genes (PCGs), 38 tRNA genes and 8 rRNA genes. A total of 16 genes contained introns, including 10 PCGs and 6 tRNA genes; the ycf3 and clpP genes contained two introns, and the remaining genes each contained one. Compared to the cp genomes of 21 other species, the cp genome of Alyssum desertorum was the smallest, which was due to variations in gene content and gene length, such as a lack of the rps16 gene and the deletion of some coding genes. Additionally, deletions of introns and intergenic spacers were observed, but their total length was not significantly shorter than those of other taxa. Phylogenetic analysis at the tribal level based on a cp genome dataset revealed that the tribe Alysseae is an early-diverging lineage and is sister to other species within subclade B of clade Ⅱ.
  • Article
    Ephemeral plants are a unique part of desert flora. They are mainly distributed in the Junggar Basin and are of great importance to the stability of dunes in the Gurbantunggut Desert. However, quantitative information on the relationship between precipitation and ephemeral plant distribution remains poorly studied. In 2009, 2011, and 2012, ephemeral plants in 73 plots located on the southern edge of Gurbantunggut Desert were investigated. Using ArcGIS 10.0 software, daily precipitation data of each plot were obtained by spline interpolation at 0.05° resolution from daily real-time gridded precipitation data of China. Using richness and coverage of ephemeral plants as the dependent variables, and precipitation during the growth period, season and month as independent variables, stepwise multivariate linear regression and principal component analysis were conducted to determine the effects of different precipitation types on the distribution of ephemeral plants and on the distribution of ten widespread and ten rare species. Results indicated that the richness of ephemeral plants was correlated with precipitation in spring, leaf expansion period, and May (classified according to different criterions), while their coverage was correlated with precipitation in spring, fruiting period and May. Precipitation in May and June had a significant impact on the widespread species, and precipitation in March, April, May and July had a significant impact on the rare species. Altogether, precipitation in May is a critical factor on the distribution of ephemerals in Gurbantunggut Desert. © 2014, Editorial Board of Chinese Journal of Ecology. All rights reserved.
  • Article
    The responses of reproduction and growth to climate warming are important issues to predict the fate of plant populations at high latitudes. Spring ephemerals inhabiting cool-temperate forests grow better under cool conditions, but how reproductive performance is influenced by warm weather is unclear. The phenological and physiological responses of reproduction and vegetative growth to warm temperature and light conditions were evaluated in the spring ephemeral Gagea lutea. Leaf and bract physiological activities, bulb growth, and seed production were compared among reproductive plants grown in forest, open, and greenhouse (GH; warming manipulation in the open site) plots. In vitro pollen germination ability was tested under various temperatures. In the GH, leaf and bract photosynthetic activities decreased rapidly at the fruiting stage, but dark respiration rates remained high, resulting in higher carbon exhaust in warm conditions. Both leaf and bract sizes and their longevities were reduced in the GH. Annual bulb growth was largest in the forest plot and smallest in the GH plot. Pollen germination was strongly inhibited at high temperature (30 °C). Fruit and seed productions were decreased only in the GH plot. Both vegetative and reproductive activities were negatively affected by warm temperature, resulting in less vegetative growth and lower seed-set, whereas an understory habitat was beneficial for vegetative growth and showed similar seed production to an open habitat over the experimental period. Decreasing population dynamics of spring ephemerals was predicted in response to future warming climate not only by growth inhibition but also by restriction of seed production.
  • Article
    A natural population of Adonis multiflora, a spring ephemeral herb growing in temperate deciduous forests, was studied to determine the seed production characteristics. Plant size, flowering time, and seed number were monitored from February 2009 to May 2011 in main growing season (i.e., from March through May). The biomass rates of the shoot and the root in the A. multiflora population were 22-24% and 76-78%, respectively, and the biomass of the root was proportional to that of the shoot. The flowering rate was 60% in the plants with 1 to 2 g of shoot biomass, and 100% in the plants with >2 g of shoot biomass. In the plants with root biomass between 4 and 6 g, the flowering rate was 43% and, in the plants with the root biomass over 8 g, it was 100%. The shoot biomass was a better predictor of the flower production probability than the root biomass. The number of flowers and seeds was closely correlated to shoot biomass at 1% significance level. The size of the plant that produced seed excessively instead of the shoot biomass in one year typically decreased in the next year and vice versa. The flowering time and its duration were closely related to the number of faithful seeds but not to that of total seeds. The number of faithful seeds was proportionate to flowering duration and inversely proportionate to flowering time (year day, YD). In a plant, the number of faithful seeds noticeably decreased with the inflorescence (i.e., order of flower in a plant), and this difference between the two successive flowers was significant at the 1% level between the first and the third flower in 2009 and 2011 but not between the third and the fourth. However, the number of total seeds was mostly similar in the first through the fourth flower for all three years. © 2014 The Ecological Society of Korea. All rights are reserved.
  • Article
    Full-text available
    Gethyllis multifolia L.Bolus and G. villosa Thunb. (Family: Amaryllidaceae) are deciduous and bulbous geophytes that occur in the succulent Karoo biome of South Africa. Both species occupy the same natural habitat, but G. multifolia is threatened and G. villosa not. Both G. multifolia and G. villosa require seasonal bulb reserves for initial vegetative and reproductive growth. In spite of G. villosa having smaller bulbs than G. multifolia, both species produce similar flower sizes and weights. The aim of the present study was to determine the carbon and nitrogen costs of vegetative and reproductive growth during the phases of growth, senescence, reproduction and dormancy of these bulbous species. The rates, costs and efficiencies of biomass production during various growth phases of the two species were determined in a comparative experiment. The results show that in spite of a significantly smaller bulb, G. villosa produced more leaves per unit bulb mass and invested more carbon and nitrogen resources into the bulbs during senescence. G. villosa also had a higher flower production, relative to bulb weight, than did G. multifolia. These physiological responses suggest that G. villosa may be more efficient at carbon and nitrogen resource utilisation.
  • Article
    According to the vernal dam hypothesis, spring ephemeral herbs temporarily sequester large nutrient pools in deciduous forests prior to canopy closure and return the nutrients to the soil following senescence of aboveground tissues. However, many species resorb nutrients from their leaves back to belowground tissues during senescence, and the degree of resorption is often associated with soil nutrient availability. Species that store large proportions of their absorbed nutrients between years are not participating in the temporary sequestering and rapid recycling of nutrients implied by the vernal dam. We investigated the extent to which Claytonia virginica L. sequestered and returned nutrients to the soil in response to nitrogen (N) and phosphorus (P) availability. We tested the effect of nutrient availability on nutrient use efficiency, resorption efficiency, and resorption proficiency (% nutrient in senescent leaves) of Claytonia. Nutrient additions significantly decreased N but not P use efficiency of Claytonia, particularly as the growing season progressed. Nutrient additions also significantly reduced N resorption efficiency from 80 to 47% and decreased P resorption efficiency from 86 to 56%. N and P resorption proficiencies were also significantly lower in senesced leaves of fertilized plants: N concentrations were 2.33% when unfertilized and 4.13% when fertilized, while P concentrations were 0.43% when unfertilized versus 0.57% when fertilized. When unfertilized, Claytonia was more efficient at resorption compared with other spring herbs, but similar to other species when fertilized. However, Claytonia was much less proficient in resorbing nutrients than other reported plants, because senescent tissues maintained substantially higher concentrations of N and P, particularly when fertilized. In conclusion, Claytonia, an important spring ephemeral species, exhibits physiological responses that emphasize its role in the vernal dam by its temporary sequestration and substantial, rapid return of nutrients in deciduous forests. Adding nutrients to the site increases the total mass and the relative proportion of nutrients that Claytonia returns to the soil rather than sequestering between seasons, which ultimately increases nutrient recycling rates within the entire system.
  • Article
    Herb composition in early spring (before leafout of hardwood overstories) was sampled quantitatively in 60 little-disturbed mesophytic hardwood stands in the Great Lakes region, USA. Disturbed hardwood stands and stands containing evergreens (hemlock) in the overstory were described by releve. Importance of strictly vernal growth forms, early spring annuals and ephemeroid perennials, was correlated with total cover of herbs. In places with nutrient-poor mineral soil, slow rates of litter decomposition, compressed growing season, or evergreen shade, populations of vernal herbs were generally sprase, with summergreen and semi-evergreen taxa relatively important. In mesophytic woods occupying physiographically similar sites, the most significant regional differences in species importance are associated with differences in soil fertility rather than climate. Superimposed on the soil-related, specific compositional differences were gradual, more general, southeast to northwest decreases in species richness, total cover of herbs, and importance of strictly vernal growth forms (annuals and ephemeroids) relative to herbs with summergreen shoots. Within stand, the most significant influences on vernal herb composition were soil drainage and microtopography. Plants with a large proportion of shoots of recent seed origin (annuals and @'weedy@' perennials) were often strongly dominant in areas with recently exposed mineral soil, as at the edges of receding vernal pools. Plants with large subterranean organs were rare in such sites. Cover of vernal herbs tended to be high on soil mounds and very low in pits, but differences in species composition were not as well defined as they are in large-area uplands vs. broad poorly drained areas. Species abundant on large patches of bare soil (as at the edges of receding vernal pools) also tended to be common in disturbed stands. Long-lived perennials with large storage organs tended to be uncommon in disturbed stands.
  • Article
    Biomass and nutrient allocation patterns were studied during the growing season in a wild leek (Allium tricoccum Ait.) population in southern Quebec, Canada Wild leek is a spring geophyte in which the photosynthetic phase precedes and does not overlap the reproductive phase N, P, K, Mg and Ca allocation to plant structures was studied concurrently with biomass allocation in reproductive plants during the 1983 growing season. Biomass allocation to individuals of all size-classes (divided into two size-classes) of the population was studied in 1984 and 1985 Patterns observed are typical of plants with a spring ephemeral phenology, such as a high investment to leaves during the short photosynthetic period The large allocation to the bulb suggests a conservative survival strategy, based primarily on vegetative propagation. Nutrient and biomass allocation patterns were largely similar, except for mobile nutrients (N and P) in the scape Little variation in biomass allocation was seen in large reproductive wild leek plants from year to year; smaller, non-reproductive plants showed higher variability, probably because of higher phenological response to climate
  • Article
    In the northern hardwood forest, growth of vernal photosynthetic herbs is temporally restricted to the period between spring snowmelt and summer canopy development. This characteristic suggests that several unique adaptations exist which allow the species to complete their life cycles, and that temporal separation of production in the herbaceous layer may add to structural and functional complexity of the ecosystem. Erythronium americanum Ker. (Liliaceae) was examined in central New Hampshire with respect to its natural history, growth characteristics and influence on energy flow and mineral cycling in the deciduous forest ecosystem. Growth leading to the early spring development of photosynthetic tissue begins with fall root growth and continues through a long winter phase during which the shoot elongates from the perennating organ, through the soil and into the snowpack. Following snowmelt, the shoots begin rapid unfurling and maturation of the photosynthetic tissue. The length of the mature leaf phase is controlled by the timing of snowmelt and canopy development, and may be quite variable between successive years. During the short period of production, total biomass increased by 190% in 1972 and 338% in 1973; however, plant weight at the end of the winter period in 1973 had decreased to 28% of the spring 1972 maximum. In the annual energy cycle, biomass losses during the nonphotosynthetic period may amount to more than production during the preceding spring. In comparison with summer green herbs, Erythronium shoot tissue contained significantly higher concentrations of N but lower levels of K, Mg and Ca, suggesting that the spring adaptation may be oriented toward higher N levels of the soil during the spring period as well as higher light levels at the forest floor. Significant correlations of biomass of vernal photosynthetic herbs with summer green species imply that temporally separated species may utilize the same physical site and resources. This adds to the structural complexity and production of the herbaceous layer; however, the vernal photosynthetics account for only 0.5% of total aboveground primary production of the ecosystem. The temporal character of Erythronium's growth and its capacity for rapid biomass accumulation combine to make it a significant factor in nutrient dynamics in the deciduous forest. Uptake of N and K during spring flushing of nutrients from the ecosystem and later release through senescence of shoot tissue appear to reduce gross ecosystem losses of these elements.
  • Article
    Full-text available
    The time-course of development of the roots and endomycorrhizas of five common herbaceous plants in a southern Ontario hardwood forest (Arisaema atrorubens, Erythronium americanum, Asarum canadense, Smilacina racemosa, and Trillium grandiflorum) was examined. Root growth of these species was very slow. Formation of vesicular-arbuscular (VA) mycorrhizas was quantified by measuring the average distance from growing root tips at which (i) hyphal contact, (ii) root penetration, and (iii) arbuscule formation by hyphae of VA mycorrhizal fungi first occurred. The rate at which mycorrhizal colonies within roots expanded was also quantified. These measurements allowed the rate of mycorrhizal colonization of roots of species to be compared. All events were slower in woodland plant roots than in other previously investigated species. The rate of VA mycorrhizal colony-expansion was found to be significantly faster in roots containing longitudinal air channels, which apparently facilitated the spread of hyphae. Environmental factors may also have been important since events were even slower in those roots produced by Erythronium in the autumn. Reasons why slow, steady, root and mycorrhiza formation could be advantageous to woodland plants are considered.