testing the role of seed size in annual legume seedling performance under experimental autumn...

Journal of Vegetation Science && (2012)

Testing the role of seed size in annual legume seedlingperformance under experimental autumnmoistureconditions

Gabriel Arellano & Begona Peco

Keywords

Autumn drought; Mediterranean therophytes;

pasture legumes; seedling survival; seedmass

Nomenclature

Flora Europea (Tutin et al. 1964–1980)

Received 17 October 2011

Accepted 18 January 2012

Co-ordinating Editor: Beverly Collins

Arellano, G. ([email protected]): Real

Jardın Botanico (CSIC), Plaza deMurillo, 2;

E-28014, Madrid, Spain

Peco, B. (corresponding author, begonna.

[email protected]): Departamento de Biologıa,

Universidad Autonoma deMadrid,

Cantoblanco, 28049, Madrid, Spain

Abstract

Question: Previous studies show that large-seeded species increase their

abundance in Mediterranean annual grasslands in growing seasons with dry

autumns. One possible explanation is that large-seeded species have larger seed-

lings, which provide an advantage under drier conditions. We address the fol-

lowing questions: is seed mass correlated with seedling survival in annual

legumes? Is this correlation influenced by the watering regime? Can seedling

growth characteristics explain the differential survival of small- and large-seeded

species?

Location: Annual Mediterranean grassland, Central Spain.

Methods: An experiment was conducted with six grassland legume species of

different seed sizes, subjected to six different watering regimes, monitoring sur-

vival andmorphological variables (shoot and root growth) for 40 d.

Results: Large seeds provide an advantage for seedling survival, but in extreme

drought conditions, seedling survival in small-seeded species equals that of seed-

lings from large-seeded species. Seedlings from larger seeds are larger than those

of small-seeded species, but have a lower root/shoot biomass ratio, leading to

greater potential evapotranspiration, which could explain their loss of relative

advantage under extreme droughts.

Conclusion: The hypothesis that seedlings from large-seeded species survive

better than small-seeded species under drought conditions was not supported.

Germination behaviour seems to be a more plausible explanation for the

increased abundance in the field of large-seeded species in growing seasons with

dry autumns.

Introduction

Floristic composition in Mediterranean grasslands under-

goes large inter-annual fluctuations. One of the key drivers

of the inter-annual fluctuations of species composition in

Mediterranean therophyte-dominated ecosystems is the

variable and unpredictable autumn precipitation (Noy-

Meyr 1973). Many observational studies relate floristic

fluctuations to fluctuations in total annual rainfall and its

distribution through the year (Peco 1989; Figueroa & Davy

1991; Hobbs & Mooney 1991; Azcarate et al. 2002; Peco

et al. 2009). Conditions during the germination stage of

individuals are especially critical (Pitt & Heady 1978;Mara-

non & Bartolome 1989), and the floristic composition of

annual pastures in spring seems to be determined before

the third month after the onset of germination in the pre-

vious autumn (Heady 1958; Espigares & Peco 1993, 1995).

The experimental study of the effect of autumn rainfall on

seed germination and seedling establishment is thus a key

factor for understanding species composition and annual

fluctuations.

Seed size is one of the functional traits suggested as a

determinant of differential responses of species to fluctuat-

ing moisture during their establishment. In arid climates,

seedling mortality is very high, mainly due to water stress

and/or competition for water with other individuals (Sol-

brig et al. 1977; Fowler 1986; Wulff 1986; Reichenberg &

Pike 1990). Observational comparative studies suggest that

plants in xeric environments have larger seeds, and

therefore a large seed might provide an advantage during

Journal of Vegetation ScienceDoi: 10.1111/j.1654-1103.2012.01394.x© 2012 International Association for Vegetation Science 1

germination and/or establishment under drought condi-

tions (Baker 1972; Sorenson & Miles 1978; Stromberg &

Patten 1990; Leishman & Westoby 1994). However, other

studies do not support this suggestion (Mazer 1989; Tele-

nius & Torstensson 1991; Tautenhahn et al. 2008).

Experimental studies are also inconclusive about the

positive effect of seed size on seedling survival under

drought conditions. Several experimental studies focusing

on intra-specific variance in seed size have found a signifi-

cant positive association between large seed size and envi-

ronmental drought (Schimpf 1977; Sorenson & Miles

1978; Stromberg & Patten 1990). Conversely, Hendrix &

Trapp (1989, 1992) showed that seedlings from small seeds

are more drought resistant in Pastinaca sativa. The few

multi-species experimental studies to date on this issue

have found a positive association between seedling sur-

vival time under drought conditions and seed size (Buck-

ley 1982; Leishman & Westoby 1994 under greenhouse

conditions) or no effect (Leishman &Westoby 1994; under

field conditions). For species in therophyte-dominated

Mediterranean grasslands, the effect of seed size on the

establishment phase under different moisture conditions

has yet to be tested experimentally, although in a long

series of observational data (Peco et al. 2009), large-seeded

plants have been found to be more abundant in dry

autumn growing seasons.

There are several reasons why larger seeds may be

advantageous for seedling establishment under drought

conditions. Large seed weight allows seedlings to spend a

proportionally larger amount of resources on growth of an

extensive root system in less time (Salisbury 1942; Steb-

bins 1971; Baker 1972; Jurado &Westoby 1992; Osunkoya

et al. 1993). However, Fenner (1983) found that plants

from large seeds had relatively small roots, while other

studies have found no relationship between seed size and

the proportional size of the root (Wulff 1986; Jurado &

Westoby 1992).

Absolute root size could also be an advantage for surviv-

ing longer under drought conditions, and may be posi-

tively related to seed size (Zhang & Maun 1991; Jurado &

Westoby 1992; Westoby et al. 1992; Osunkoya et al.

1993). A stronger elongation response in seedlings from

large-seeded species under low moisture conditions has

also been documented (Leishman &Westoby 1994). How-

ever, absolute root size is also related to shoot size, and

therefore might not always be an advantage under condi-

tions of water stress, due to higher evapotranspiration and

possibly lower water use efficiency in large vs small seed-

lings (Leishman &Westoby 1994; Leishman et al. 1995).

In the present study, a range of annual legume species

with different seed sizes was used under controlled experi-

mental conditions to test the hypothesis that large seed

sizes provide an advantage for seedling survival under low

soil moisture conditions. The relationship between seed-

ling morphological variables and seedling survival was also

explored. The specific questions we address are: is seed

mass correlated with seedling survival in annual legumes;

is this correlation influenced by the watering regime; and

can seedling growth patterns explain the differential sur-

vival of small- and large-seeded species?

Methods

Seed collection and seedmass

Six abundant legume species in central Iberian grasslands

were chosen to represent the widest possible seed weight

gradient. Seed weights for the whole community ranged

from 0.009 to 6.5 mg (0.24 to 2.064 mg for annual

legumes only) and showed a right-skewed distribution

with a median of 1.5 mg (Peco et al. 2003). The study was

restricted to legumes due to the agricultural interest in this

family, and also to avoid confusion between treatment

effects and phylogenetic variability. The seeds of all species

were collected in the same habitat (dry grasslands) in a

100-ha open woodland, the Moncalvillo dehesa; 40° 41′N,3° 36′W, ~ 800 m a.s.l.) 15 km north of Madrid (Spain).

We collected all the seeds from at least ten individuals per

species located more than 100 m apart. Seeds were col-

lected in July 2004 and stored under dark lab conditions in

paper bags at room temperature (~ 20 °C).The study area is an open forest of Quercus ilex L. subsp.

ballota with annual-dominated grassland. Soils are sandy,

shallow and acidic over a gneiss substrate, and the climate

is continental Mediterranean with an average of 550 mm

of annual rainfall and strong inter-annual fluctuations.

Rainfall is concentrated into autumn–winter–spring, with

a long dry period during summer. Germination of annual

grassland species starts after the first autumn rains and is

mainly concentrated in the autumn (Ortega et al. 1997).

Batches of 500 clean seeds from each species (1500 in

the case of Trifolium glomeratum because of its small size)

were weighed using a balance with 0.0001 g accuracy. The

six selected legume species and their seed weights were:

Trifolium cherleri L. (2.33 mg), T. striatum L. (1.93 mg),

T.angustifolium L. (1.91 mg), Biserrula pelecinus L. (1.11

mg), Anthyllis lotoides L. (0.99 mg) and T. glomeratum L.

(0.44 mg).

Seedling collection

The seeds were scarified using fine-grained wood sandpa-

per to abrade batches of 20–30 seeds at a time for 5 min,

applying constant pressure and circular movement. After

scarification, germination took place in a phytotron. The

photoperiod used was 12-h light/12-h dark, 20 °C/15 °Cday/night temperature, equivalent to the average

Journal of Vegetation Science2 Doi: 10.1111/j.1654-1103.2012.01394.x© 2012 International Association for Vegetation Science

Seed size and seedling survival under drought G. Arellano and B. Peco

conditions between September and October in the study

area (Espigares & Peco 1995). The scarified seeds were

placed in closed Petri dishes with saturated, but not drip-

ping, filter paper on a saturated exfoliated vermiculite

base. Seed density was 70–100 seeds per plate.

Once the radicle emerged (usually within 48 h), ten

pre-germinated seeds from each species were transplanted

to 5 9 5 9 5 cm seedling tray cells filled with loose,

stone-free sand, previously moistened with 20 ml water.

The sand was completely dry before starting the experi-

ment (0% humidity sensor measured with a ML2 Delta T

Inc. ML2 Theta Probe Meter and HH1 Theta reader, using

the mineral soil function). Prior to transplanting the pre-

germinated seeds, the corresponding dose of 2.2 g slow

release fertilizer (NPK) per litre of soil was added to each

cell. Pre-germinated seeds were inserted with the radicle

pointing downwards at a shallow depth in narrow

1–2 mm holes. Each cell then received 10 ml water. Since

the most delicate moment for seedlings in the experiment

is the transfer from the Petri dish to the cell, this initial

30 ml water per cell was applied during transplantation in

all cases, regardless of the subsequent watering treatment,

in order to prevent high initial mortality (Leishman &

Westoby 1994).

Seedling survival and growth vs water availability

A phytotron experiment was conducted using the same

photoperiod and temperature conditions described for the

seedling production stage, with different watering treat-

ments. There were six watering levels, with a range of soil

moisture from sand that was almost flooded during water-

ing to almost completely dry sand: 5 ml/2 d, 10 ml/2 d,

15 ml/2 d, 20 ml/2 d, 25 ml/2 d and 30 ml/2 d. The

watering treatment began on the day after the pre-

germinated seeds were transplanted to the cells. We also

measured the 2-d average soil water content with Theta

probes in control pots (without seedlings). These data were

transformed into available water content using the values

of soil bulk density of the substrate used in the experiment

(Briggs & McLane 1907). The resulting 2-d averages of

available gravimetric water for the different watering treat-

ments were: �0.31, 1.00, 2.32, 3.64, 4.96 and 6.28%,

respectively. These values fit into the monthly measure-

ments of available water content range observed in the

field in dehesa ecosystems of western Spain with similar

soils (Cubera &Moreno 2007).

Seedling cells containing pre-germinated seeds from six

species were placed on trays with a total of ten replicates

per species and watering treatment. A sample consisting of

one tray per watering treatment was collected every 4 d.

This was used to quantify the seedling survival percentage

in each species. Seedlings were harvested to measure the

following morphological variables: total dry weight, maxi-

mum root length, dry shoot weight and dry root weight.

Dry weight was measured after drying the harvested seed-

lings for 48 h at 80 °C in an oven. Morphological variables

for each species and treatment were calculated as the aver-

age of the surviving plants in each cell.

The experiment was conducted for 40 d to generate ten

data points for time of survival and average morphological

variables for the surviving seedlings from each species and

watering treatment.

Data analysis

The influence of factors (time, watering, seed size) on sur-

vival and morphological variables (dry weight, root length

and root/shoot ratio, henceforth R/S) was analysed using

univariate general linear models. Seed weight was used as

a factor with two levels: large seed (seed mass >1.5 mg)

and small seed (seed mass <1.5 mg). Watering was also

included as a factor by grouping the treatments into three

levels: high (25–30 ml/2 d, medium (15–20 ml/2 d and

low (5–10 ml/2 d). Time was fed into the model as a co-

variate. The number of replicates for each combination of

factors was six for each time. Given that none of the

response variables fulfilled the symmetry assumption, they

were all transformed to generate symmetric variables, for

which the analysis is robust. To understand the possible

underlying mechanisms that may explain survival, a series

of nonparametric bivariate correlations (Spearman Rho)

was generated between survival and morphological vari-

ables, using residuals for time and watering. The effect of

time and watering distorts our understanding of the corre-

lations between morphological traits and survival (e.g.

older plants are more likely to be dead and moreover have

the longest roots, although this does not mean that having

long roots implies being less able to survive). We therefore

used residuals, subtracted from the observed data for the

average of observations with the same time and the same

watering. Spearman correlations were made for the full

data set and for each separate watering treatment in order

to detect differences between watering treatments in sign

and intensity of correlations between survival and seed

weight or seedling morphology. SPSS 15.0 (Chicago, IL,

US) was used in all analyses.

Results

Effect of time, watering and seedweight on seedling

survival

The univariate general linear model explaining survival

(corrected R2 = 21.5%) showed a significant effect of time

(F = 72.02,P < 0.001) and significant interactions between

watering and time (F = 5.695, P = 0.004), and between


G. Arellano and B. Peco Seed size and seedling survival under drought

seed size and watering (F = 2.90, P = 0.057). For this rea-

son, models were generated for each watering level (high,

medium and low). The best model for survival at the high

watering level included a time effect (F = 11.24,

P = 0.002) and seed size (F = 13.03, P < 0.001). In this

treatment, small-seeded species showed lower survival

than large-seeded species (Fig. 1a). However, seed size was

not significant for medium (F = 1.60, P = 0.21) and low

watering models (F = 0.08, P = 0.78), although the time

effect was significant (F = 21.78, P < 0.001 and F = 42.51,

P < 0.001, respectively; Fig. 1b,c).

Effect of watering and seed size on seedling growth

Both total dry weight and root length increased signifi-

cantly with time for all seedlings (Table 1, Fig. 2a,b). For

these growth variables, the effect of watering was only sig-

nificant for seedlings of large-seeded species, in which

there was a decrease in growth when the watering level

decreased (Fig. 2a,b). In the case of the R/S ratio, there

was a significant interaction between watering and time

for both types of seedling. In both cases, reduced watering

resulted in a greater relative root weight, which was more

pronounced in seedlings from small-seeded species

(Fig. 2c).

Survival vs seedweight and seedlingmorphology

We found significant positive correlations between sur-

vival and growth variables for the full data set (N = 299):

root length (r = 0.29, P < 0.001), dry root weight (r =0.22, P < 0.001), dry shoot weight (r = 0.19, P = 0.001)

and total dry weight (r = 0.22, P < 0.001). However, no

significant correlation with relative root weight was

detected (r = 0.09, P = 0.123). All growth variables were

positively and significantly correlated with seed size: root

length (r = 0.29, P < 0.001), dry root weight (r = 0.32,

P < 0.001), dry shoot weight (r = 0.57, P < 0.001) and

total dry weight (r = 0.51, P < 0.001), with the exception

of relative root weight, which had a significant negative

correlation with seed size (r = �0.20, P < 0.001). We also

found that plants with large seeds survive longer, with a

significant positive correlation between seed size and sur-

vival (r = 0.16, P = 0.004).

When analysed separately, the results for high watering

and low watering were quite different (Table 2). While in

high watering situations, seedling size correlated positively

with survival, the trend was reversed with low watering

and larger seedlings (greater total dry weight, dry shoot

weight and dry root weight) showed significant and nega-

tive correlations with survival.

Discussion

The results of this experiment show that less seedlings of

small-seeded species survive than those of large-seeded

species under high watering conditions (20 and 30 ml

every 2 d). However, with medium-low watering (5–

20 ml every 2 d), survival of seedlings from small-seeded

species does not differ from large-seeded species. These

results seem to conflict with the hypothesis that having

large seeds can provide an advantage when establishing

seedlings under drought conditions. This hypothesis has

some evidence in its favour on the basis of observational

and experimental data (Baker 1972; Sorenson & Miles

1978; Stromberg & Patten 1990; Leishman & Westoby

1994; Peco et al. 2009), although other authors such as

Fenner (1983) and Hendrix & Trapp (1989, 1992) have

found that under drought conditions, seedlings of small-

seeded species are more likely to survive.

The analysis of seedling growth in relation to watering

treatment shows that seedlings subjected to low watering

Fig. 1. Differences in survival trends between different experimental watering treatments. s axis shows survival percentage.



Table 1. Summary of general linear univariate model results for different morphological variables.

Large seeds Small seeds

Watering Time Watering*Time Watering Time Watering*Time

F P-value F P-value F P-value F P-value F P-value F P-value

TDW 7.36 0.001 905.34 <0.001 – – 1.14 0.322 704.08 <0.001 – –

RL 3.52 0.032 408.65 <0.001 – – 0.21 0.806 621.36 <0.001 – –

R/S 2.74 0.069 1.28 0.260 10.20 <0.000 0.81 0.444 1.25 0.266 10.66 <0.001

Significant correlations (P < 0.05) are shown in bold. TDW, total dry weight; RL, maximum root length; R/S, root/shoot dry weight ratio.

Fig. 2. Changes with time in seedling total dry weight (a); maximum root length (b); and relative root weight (c). Different lines represent different watering

treatments.



respond by developing a larger root system (absolute and

relative). This is possibly mediated by a hormonal response

guided by abscisic acid (ABA). Under dehydration condi-

tions, ABA levels increase, which ultimately leads to a

strong positive effect on root growth and a slightly negative

effect on stem growth (Taiz & Zeiger 2006). Because it is a

hormonal response, the typically high R/S ratios in plants

under water stress emerge over time, hence the positive

correlation of R/S ratios with time under low watering but

not under high watering. ABA is unable to inhibit shoot

growth, which continues to grow as the plant under water-

ing stress increases its R/S ratio. The fact that the shoot

inevitably keeps growingmay be decisive for seedling mor-

tality under lowwatering treatments.

Like other authors (e.g. Fenner 1983), we have found

evidence that large-seeded species have seedlings with a

lower relative root weight than small-seeded species. Our

interpretation of this finding, and its relation to the rela-

tively lower survival of large-seeded plants in drought con-

ditions, is not that the roots of these seedlings are too

small, but that their shoots are too large. Having a high R/S

ratio is a more characteristic feature of seedlings from

small-seeded species. In general, this strategy is only useful

for the survival of seedlings, which have larger roots in

absolute terms. However, seedlings from small-seeded spe-

cies have a high root elongation response under the low

watering treatment, developing a higher R/S ratio than the

seedlings of larger-seeded species under the same circum-

stances, as they manage to increase the size of their roots

without the shoot growing excessively. In spite of this,

they cannot equal the seedlings of large-seeded species in

terms of absolute root size, and the survival of both types

of seedlings is similar.

In which case, is it therefore profitable or sufficient to

have small seeds and be smaller? Why do plants with

large seeds and small seeds co-exist in the same ecosys-

tem? Our results for the correlation between morpho-

logical variables and seedling survival show that under

high watering (20, 25 and 30 ml/2 d), seedlings from

large-seeded species have long roots and a large shoot,

which leads to greater survival. In the 15 ml/2 d treat-

ment, total size and shoot size showed no relation, while

root length, dry root weight and R/S correlated posi-

tively with survival. We therefore conclude that under

these slightly lower watering conditions, investing in

shoot growth is not as beneficial (ultimately it is a cost),

while the development of a large root system remains

an advantage. In the 10 ml/2 d treatment, there was no

correlation between any of the variables with survival,

and a change in trend seemed to occur under an inter-

mediate watering treatment, given the opposite trend to

all of the above found under the 5 ml/2 d treatment:

seedling size correlated significantly and negatively with

survival, probably due to excessive and disproportionate

shoot growth, which causes levels of evapotranspiration

that the plant cannot cope with.

Peco et al. (2009), exploring the relationship for the

whole community between species abundance and

autumn precipitation over a 16-yr period in permanent

field plots in the same ecosystem and study area, found

that large-seeded species were more abundant in the vege-

tation after dry autumns and small-seeded species were

more abundant after wet autumns. The re-analysis using

data from Peco et al. (2009) for only legume species show

the same pattern. Average seed mass was higher for the

group of species in which abundance correlate negatively

with autumn rainfall than for the group of species inwhich

abundance correlate positively with autumn rainfall

(t-test, P = 0.03). Peco et al. 2009 hypothesize that plants

with large seeds survive better and are more abundant in

dry autumns, possibly due to their larger absolute root size,

which is generally characteristic of larger seedlings. Never-

theless, the results of the present study do not support this

hypothesis. In this paper we find that seed weight corre-

lates positively with survival but only under the less severe

watering regime, because large-seeded species tend to have

seedlings with a lower R/S ratio than small-seeded species.

Thus, having a big seedling can be negative under drought

conditions, probably because of the increased evapotrans-

piration rate.

Table 2. Significance of correlations between survival and variables, analysing each watering level separately. Data are residuals after controlling for the

effect of time and watering.

Watering

(ml/2 d)

Available

water %

N Seed mass R/S Shoot length Root length Dry root weight Dry shoot weight Total dry weight

5 �0.32 20 0.215 0.301 0.962 0.269 0.016 (�0.53) 0.032 (�0.48) 0.034 (�0.48)

10 1.00 50 0.583 0.907 0.407 0.152 0.437 0.321 0.227

15 2.32 50 0.500 0.010 (+0.36) 0.615 0.009 (+0.37) 0.017 (+0.34) 0.804 0.175

20 3.64 60 0.030 (+0.28) 0.300 0.229 0.003 (+0.37) 0.041 (+0.26) 0.067 (+) 0.055 (+)

25 4.96 59 0.010 (+0.33) 0.616 0.062 (+) 0.000 (+0.50) 0.000 (+0.49) 0.000 (+0.49) 0.000 (+0.50)

30 6.27 60 0.005 (+0.36) 0.224 0.047 (+0.26) 0.000 (+0.49) 0.003 (+0.37) 0.002 (+0.39) 0.002 (+0.40)

P-values < 0.05 are shown in bold, with the value of this correlation in brackets. N, number of replicates (the different number of replicates per treatment is

due to seedling mortality). Two-days average available gravimetric water content is also indicated for each watering treatment.



In our experimental setting we tried to replicate the

water availability experienced by this type of vegetation in

autumn using a range from�0.32% to 6.28% (gravimetric

percentages). We only found one field study with monthly

measurements of water availability in dehesa systems with

similar soils and climate in the period between July 2003

and November 2005 (Cubera & Moreno 2007). These

authors found that available water content in autumn ran-

ged from �4.5 to 7.0%, corresponding to an accumulated

2 mo rainfall of 50–200 mm, respectively. These values

are quite similar to those observed by Peco et al. (2009) in

a 16-yr series (0–170 mm). Although there are consider-

able limitations to relating experimental and field condi-

tions, on the basis of the few published data from similar

systems we can assume that our experiment reflects fluc-

tuations in the autumn available water content under a

natural precipitation regime in the field.

One possible explanation for the pattern observed in the

field could be related to the time of imbibition required for

the germination of non-dormant seeds. Fast germinators

have a competitive advantage if post-germination condi-

tions remain favourable, but slow germinators are

favoured when the rapid germinators are killed in a subse-

quent dry period. The analysis of experimental data on

seed germination under controlled optimal conditions in

our group shows that small-seeded Mediterranean annual

species germinate earlier than large-seeded species

(r = 0.48, P = 0.04; Fig. 3). Small-seeded species germi-

nate earlier and therefore take more risks in the case of

post-germination droughts, but have the advantage of

early germination for plant fitness in case of favourable

weather conditions (Espigares & Peco 1995; Verdu & Tra-

veset 2005). In years with dry autumns, most small-seeded

species seedlings die, resulting in a positive association

between large-seeded species and this type of year, as

shown in Peco et al. (2009). Squella (1992) also found that

small seeds in Australian annual legumes tend to germi-

nate earlier than large seeds. According to the this author,

small seeds have higher initial germination rates because

they can break the physical dormancy more easily (appli-

cable to legumes) and absorb water more quickly than

large seeds (extended to non-legumes as well, given that

their water absorption through the surface means that the

absorption rate depends on the surface/volume ratio,

which is always higher in small seeds).

Overall, the hypothesis that seedlings from large-

seeded species survive better than seedlings of small-

seeded species under dry conditions was not supported.

In the extreme conditions used here, the benefits of

having a big seed are counterbalanced by the cost of

increased evapotranspiration. Germination behaviour

could be a more plausible explanation for the increased

abundance in the field of large-seeded species in years

with dry autumns, although the potentially important

role of intra-specific variability and other multiple inter-

actions in explaining vegetation dynamics in the field

must not be ignored.

Acknowledgements

Special thanks to Iker Dobarro for assistance with labo-

ratory equipment and the phytotron, and for valuable

comments on physiology of the plants involved. This

study was funded by Spanish Ministry of Science and

Technology (projects CGL2007-63382 and CGL2011-

24871) and Madrid Regional Government (project

S2009-AMB-1783). We also thank the Spanish Ministry

of Education for a mobility grant (PR2011-0491) for

Begona Peco.

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testing the role of seed size in annual legume seedling performance under experimental autumn...

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