Gender differences in phenotypic plasticity and adaptive response of Seabuckthorn ( Hippophae rhamnoides L.) along an altitudinal gradient in trans-Himalaya

Abstract

BACKGROUND::

In dioecious plants, morphological adjustment to climate change may differ between male and female individuals due to greater reproductive effort in females. Not accounting for sexual variation could lead to incorrect assessment of a species response to climate change.

OBJECTIVES:

The aim of this study was to assess how important gender-specific responses are to Hippophae rhamnoides in changing trans-Himalayan environments.

METHOD:

Leaf morphological characters of male and female Hippophae rhamnoides individuals along an altitudinal gradient (2797-4117 m) and plants raised in ‘common-garden’ experiment was measured. RESULTS: Leaves become smaller in length and area, but became thicker with decreasing specific leaf area (SLA) with increasing altitude in both the gender. Leaf size, area, thickness, chlorophyll and petiole length were found to be higher in males than in females, while female had a higher SLA. When cuttings from the plants were grown in a common-garden experiment, the altitudinal effect disappeared for all morphological variables suggesting that most leaf morphological variation in H. rhamnoides is environmentally determined. In the event of climate change, our study showed that phenotypic plasticity would be a crucial determinant of plant response in mountainous region. Effect of altitudinal gradient on leaf morphology was more conspicuous in males suggesting that males are more responsive to change in environmental conditions..

CONCLUSION:

The results suggested that males will adapt better to the changing climate and may lead to a male-biased population in the event of climate change. Stressful environments cause added detrimental impact on female than on male.

Keywords

Abiotic stress adaptation climate change plasticity Ladakh

1 Introduction

Climate change is altering the availability of resources and the conditions that are crucial to plant performance [1]. Over the last few decades, attention is being increasingly focused on evolutionary responses to rapid climate change [2]. One major concern in this context relates to the ability of long-lived species to cope with rapid change in climate [3 –5]. Plant species can adjust to changing climate through environmentally induced shift in phenotype (phenotypic plasticity), adapt through natural selection (genetic response) or migrate to follow conditions to which they are adapted; these options are not mutually exclusive [1]. However, studies on climate change-induced evolution under simulated and natural climatic conditions have rarely integrated plastic and genetic evolutionary responses [6]. In dioecious plants, morphological adjustment to climate change may differ between male and female individuals due to greater reproductive effort in females. The cost of reproduction involves prioritization of resources for fruit development rather than for vegetative growth or protection in females. A major investment in reproduction is generally associated with the disadvantage in terms of oxidative stress and cellular injuries, particularly under adverse conditions [7]. Not accounting for sexual variation could lead to incorrect assessment of a species response to climate change [8]. However, this aspect has not been studied in detail, particularly in the fragile trans-Himalayan region.

Both abrupt and gradual climate changes will impose selection on plant population [1]. Abrupt climate changes will result in rapid harsh selection for more stress-tolerant genotypes, whereas gradual climate changes are expected to impose soft selection mediated by intraspecific interactions [6]. Altitudinal gradients in stressful mountain ecosystem provide an ideal experimental opportunity for studying the functional traits of plants in response to abrupt climate change. In mountainous regions, sharp changes in abiotic factors occur over short distances, leading to major changes in the selection pressures acting on plant life history traits [2].

Altitude has a major effect on leaf morphology and physiology within a species. Leaves generally decrease in length, width and area but become thicker with increasing altitude [9 –11]. However, the problem in interpreting the well documented relationship between altitude and leaf morphology is the confounding of environmental and genetic factors [10]. There are evidences that plant originating from different altitudes remain different when grown at same altitude [10 , 13]. Cordell et al. [14] reported that leaf morphology is largely genetically determined but leaf anatomy and physiology are environmentally determined in tree species Metrosideros polymorpha. Hovenden and Vander Schoor [10] found that the morphological response to the environment generally overrides the genetic influence in Nothofagus cunninghamii. A similar study showed that the extensive altitudinal distribution of Pennisetum setaceum is the result of ecological tolerance rather than adaptation of specific ecotype [15]. At extreme altitude (above 2800 m) the relationship between leaf morphology and altitude differed from the conventional linear relationship along altitudinal gradients [16], but this aspect has not been studied in details. Thus it appears that the degree of environmental plasticity and adaptation is species and environment dependent.

Hippophae rhamnoides L. is an ecologically and economically important dioecious plant. It is found in a large altitudinal range, from the sea shores in Europe to over 4694 m in trans-Himalayan Ladakh. Leaf morphological characters including leaf size, thickness and specific leaf area (SLA) are strongly influenced by altitude and gender in this species [16]. However, leaf morphological traits of H. rhamnoides measured in natural conditions have not been investigated in concert with measurements of their progeny in common garden experiments. H. rhamnoides are easy to propagate by stem cuttings, and the availability of clonal material facilitates the testing of identical genotypes under different conditions. H. rhamnoides, therefore, presents an excellent opportunity to investigate the relative contributions of environmental, genetic and gender factors to the relationship between leaf morphology and altitude. The aim of this study was, therefore, to assess how important gender-specific responses are to H. rhamnoides in rapidly changing trans-Himalayan environments. This was done using a ‘common-garden’ experiment, in which large number of cuttings from several male and female shrubs at each of four altitudinal range was grown in a single experimental plot.

2 Materials and methods

2.1 Study site

The study was conducted in trans-Himalayan Ladakh region. The altitude of origin of field-grown plants ranged from 2797–4117 m amsl (Table 1). Common-garden experiment was carried out at an experimental farm (34°08.2’N; 77°34.3’E, elevation 3350 m) on a flat site with direct sunshine at Defence Institute of HighAltitude Research (DIHAR) in trans-Himalayan Ladakh, India. The mean maximum and minimum temperature during 2014–2015 recorded at DIHAR was 12.9±8.8°C and –0.2±9.0°C, respectively. The monthly maximum temperature was highest in July (25.6°C), and the minimum temperature was recorded lowest in January (–13.2°C). The mean maximum and minimum relative humidity was 31.0±4.3% and 24.7±3.7%, respectively. The average annual precipitation was 163 mm.

Table 1
Geographical location and sampling sites of Hippophae rhamnoides in trans-Himalaya Ladakh

Altitude ranges (m amsl) Population Altitude (m amsl) No. of samples

Male Female

2800–3000 Turtuk 2797 2 2

Hundar 2890 1 1

Diskit 2910 1 1

Nurla 2990 1 1

3001–3300 Phey 3179 1 1

Panamik 3180 1 1

Shey 3232 2 2

Achinathang 3255 1 1

3500–3800 Shayok I 3576 1 1

Chemday 3680 1 1

Shayok II 3740 1 1

Durbuk 3850 1 1

3801–4200 Horzey 3885 2 2

Sakti 3927 1 1

Khardong 4117 1 1

Altitude ranges (m amsl)	Population	Altitude (m amsl)	No. of samples
2800–3000	Turtuk	2797	2	2
	Hundar	2890	1	1
	Diskit	2910	1	1
	Nurla	2990	1	1
3001–3300	Phey	3179	1	1
	Panamik	3180	1	1
	Shey	3232	2	2
	Achinathang	3255	1	1
3500–3800	Shayok I	3576	1	1
	Chemday	3680	1	1
	Shayok II	3740	1	1
	Durbuk	3850	1	1
3801–4200	Horzey	3885	2	2
	Sakti	3927	1	1
	Khardong	4117	1	1

2.2 Leaf analysis

Between 13 and 25 August 2014, a single branch was collected from each of 8–10 adult H. rhamnoides shrubs from four altitudinal range. All branches were collected on the sunny side of the shrub. Samples of young fully expended leaves (10 leaves per plant) were collected from each branch to investigate the field-grown leaf characteristics. Between 04 and 14 April 2015, dormant cuttings of pencil thickness were taken from each shrub and planted at an experimental farm at DIHAR. Samples of fully expended leaves (10 leaves per plant) were collected in September 2015 from each of the rooted plants to record the garden-grown leaf characteristics. Both field and garden-grown leaves were evaluated for leaf gross morphology. Leaf length, width, thickness were measured using digital calipers (CD-6“CS, Mitutoya, Japan). Leaf length was measured from the base of petiole to leaf tip, while leaf width was recorded at the maximum width of the blade. Leaf thickness was measured from the central part of the lamina, half-way between midrib and margin. Petiole length was taken by cutting the petiole portion of the leaf from base of the leaf blade, while chlorophyll was measured with Chlorophyll Meter SPAD-502 (Konica Minolta Sensing Inc., Japan). Leaf area was measured with a portable leaf area meter (CI 202) (CID Inc, Camas, WA, USA). Leaves were shade-dried to constant mass at 60°C. SLA was calculated by dividing one-sided fresh leaf area by the drymass.

2.3 Statistical analysis

Assumptions of normality were checked for all variables with Kolmogorov-Smirnov test and variables that significantly deviated from normality were log transformed. Tukey’s HSD test was performed at p≤0.05 level for mean comparison. One-way analysis of variance (ANOVA) and regression was conducted with altitude as the fixed factor and leaf morphological parameters as dependent variable. A two-way ANOVA was used to test the relationship of gender, altitude and their interaction with leaf morphological characters. Coefficient of variation (CV) for each trait as a complementary index to interpret the plasticity was computed using the formula: CV = standard deviation×100/mean. Statistical analysis was carried out in MS excel 2007 and SPSS software package v.17.0 for Windows (SPSS Inc. released in 2008).

3 Results

3.1 Gender differences in phenotypic variation along altitudinal gradient

Both altitude and gender had a significant impact on selected leaf morphology of field-grown H. rhamnoides (Table 2). Leaves become smaller in length and area, but became thicker with decreasing SLA with increasing altitude in both the gender. Effect of altitudinal gradient on leaf thickness was more evident in male. The linear regression showed almost linear (R² = 0.82) relation between leaf thickness with altitude in male, but there was no linear relationship in female (R² = 0.02) (Table 3). Petiole length in males increased significantly with increasing altitude (R² = 0.44), but similar pattern was not observed in females (R² = 0.04). No significant relationship with altitude was observed for leaf width in both the gender. The chlorophyll contents varied between ‘high’ and ‘low’ altitudes, with leaves from higher altitude (3500–4200 m) having more than those from lower altitude (2800–3300 m) in both the gender.

Table 2
One way ANOVA in filed grown and common garden grown plants and their difference in different sexes

Gender	Growing condition	Altitude (m amsl)	LL	LW	LT	LA	PL	CC	SLA
Male	Field	2800–3000	35.60 ± 7.85^d	3.75 ± 0.32^a	0.26 ± 0.01^ab	1.41 ± 0.30^d	1.66 ± 0.12^a	58.35 ± 5.46^bcdef	0.21 ± 0.05^ab
		3001–3300	30.65 ± 6.62^abcd	4.37 ± 0.73^a	0.28 ± 0.03 ^abcd	1.28 ± 0.40^ab	2.10 ± 0.69^ab	62.15 ± 11.78^cdef	0.13 ± 0.04^ab
		3500–3800	31.73 ± 3.49^abcd	4.31 ± 1.23^a	0.36 ± 0.03^bc	1.27 ± 0.40^abcd	2.23 ± 0.1^ab	72.59 ± 6.76^f	0.14 ± 0.06^ab
		3801–4200	28.99 ± 5.09^abcd	3.68 ± 0.57^a	0.37 ± 0.03^c	1.14 ± 0.26^abcd	2.64 ± 0.28^b	71.74 ± 4.86^ef	0.11 ± 0.03^a
	Garden	2800-3000	32.52 ± 5.95^bcd	3.58 ± 0.86^a	0.28 ± 0.05^abc	1.12 ± 0.37^abcd	1.65 ± 0.38^a	63.47 ± 6.21^cdef	0.15 ± 0.03^ab
		3001–3300	26.08 ± 4.72^abcd	3.51 ± 0.75^a	0.29 ± 0.07^abc	0.86 ± 0.35^abcd	1.85 ± 0.52^ab	74.79 ± 4.61^f	0.11 ± 0.05^a
		3500–3800	33.20 ± 5.28^cd	3.04 ± 0.37^a	0.25 ± 0.09^a	0.94 ± 0.16^abcd	2.17 ± 0.12^ab	69.57 ± 7.42^def	0.09 ± 0.03^a
		3801–4200	29.07 ± 2.80^abcd	3.61 ± 0.25^a	0.31 ± 0.04^abc	0.96 ± 0.16^abcd	2.17 ± 0.24^ab	69.36 ± 6.89^def	0.09 ± 0.02^a
Female	Field	2800–3000	24.79 ± 1.73^abcd	3.05 ± 0.31^a	0.28 ± 0.04^abc	0.75 ± 0.12^abc	1.58 ± 0.36^a	40.48 ± 1.05^a	0.27 ± 0.11^b
		3001–3300	23.21 ± 2.23^abc	3.58 ± 0.61^a	0.26 ± 0.03^ab	0.73 ± 0.16^abc	1.45 ± 0.16^a	50.45 ± 4.30^abc	0.26 ± 0.11^ab
		3500–3800	21.78 ± 4.16^ab	3.34 ± 0.62^a	0.29 ± 0.04^abc	0.71 ± 0.29^abcd	1.41 ± 0.17^a	55.16 ± 9.85^abcde	0.17 ± 0.02^ab
		3801–4200	20.97 ± 4.98^a	3.12 ± 0.60^a	0.32 ± 0.06^abc	0.62 ± 0.21^ab	1.46 ± 0.14^a	52.70 ± 1.94^abcd	0.17 ± 0.05^ab
	Garden	2800–3000	21.71 ± 4.64^ab	3.43 ± 0.37^a	0.28 ± 0.02^abc	0.74 ± 0.14^abc	1.54 ± 0.15^a	41.14 ± 5.99^ab	0.23 ± 0.04^ab
		3001–3300	21.53 ± 2.23^ab	3.28 ± 0.39^a	0.28 ± 0.03^abc	0.66 ± 0.09^abc	1.56 ± 0.35^a	59.38 ± 12.19^cdef	0.19 ± 0.05^ab
		3500–3800	21.47 ± 2.36^ab	2.99 ± 0.24^a	0.25 ± 0.05^a	0.55 ± 0.09^a	1.52 ± 0.12^a	52.95 ± 2.88^abcd	0.21 ± 0.07^ab
		3801–4200	21.95 ± 3.65^abc	3.33 ± 0.61^a	0.29 ± 0.02^abc	0.64 ± 0.17^abc	1.39 ± 0.10^a	54.60 ± 3.61^abcde	0.17 ± 0.04^ab

LL = leaf length (mm), LW = leaf width (mm), LT = Leaf thickness (mm), PL = Petiole length (mm), LA = Leaf Area (cm²), CC = Chlorophyll contents (SPAD VALUE), SLA = Specific leaf area (cm^2//mg). Values represented as mean ± SD; for each column, different lowercase letters indicate significantly different at P < 0.05, as measured by 2-sided Tukey’s HSD.

Within each altitude, there was a significant influence of gender on selected morphological characters measured. Leaf length, width, thickness, area and chlorophyll contents were higher in males than in females (Table 2). The effect of altitude and gender on leaf morphology was supported by results of two-way ANOVA (Table 4). Predominant effects of altitude on leaf length (F₁ = 3.8, p≤0.05), thickness (F₁ = 3.8, p≤0.05), petiole length (F₁ = 3.3, p≤0.05), chlorophyll contents (F₁ = 3.0, p≤0.05), and SLA (F₁ = 12.0, p≤0.001) was observed. Similarly, significant effect of gender was observed on leaf width (F₁ = 7.0, p≤0.05), thickness (F₁ = 4.4, p≤0.05), area (F₁ = 7.5, p≤0.05) and SLA (F₁ = 7.3, p≤0.01). Males showed more variability than females in all the leaf morphological traits except for leaf thickness (Table 5).

Table 3

Regression analysis with altitude as independent variable and field- and garden-grown leaf of Hippophae rhamnoides as dependent variable

Parameters	Male				Female				Mixed (male + female)
	Field-grown		Garden-grown		Field-grown		Garden-grown		Field-grown		Garden-grown
	R²	P	R²	P	R²	P	R²	P	R²	P	R²	P
Leaf Length (mm)	0.08	0.243	0.55	0.351	0.01	0.840	0.00	0.892	0.05	0.374	0.02	0.607
Leaf width (mm)	0.02	0.592	0.03	0.484	0.02	0.583	0.02	0.739	0.05	0.377	0.01	0.708
Leaf thickness (mm)	0.82	0.000	0.20	0.050	0.02	0.542	0.01	0.728	0.51	0.001	0.23	0.045
Petiole Length (mm)	0.44	0.003	0.03	0.522	0.04	0.230	0.09	0.237	0.41	0.004	0.11	0.178
Leaf Area (cm²)	0.06	0.330	0.01	0.712	0.03	0.518	0.05	0.379	0.07	0.303	0.04	0.452
Chlorophyll contents (SPAD)	0.09	0.234	0.37	0.008	0.00	0.868	0.13	0.140	0.04	0.412	0.28	0.025
Specific leaf area (cm²/mg)	0.34	0.010	0.26	0.033	0.31	0.016	0.08	0.247	0.48	0.002	0.37	0.008

Table 4

Two-way ANOVA for leaf morphological characters of Hippophae rhamnoides with gender and altitude as main effects

Growing condition	Source	Df	F
			LL	LW	LT	PL	LA	CC	SLA
Field-grown	Sex	1	0.775	7.037*	4.413*	1.855	7.456*	1.462	7.274**
	Altitude	3	3.817*	0.354	3.864*	3.298*	2.349	2.971*	12.003***
	SXA	3	0.865	1.670	3.316*	0.347	0.494	0.788	0.292
Garden-grown	Sex	1	0.555	0.315	1.216	0.274	1.094	1.036	0.803
	Altitude	3	0.419	0.949	1.530	0.474	0.714	3.538*	1.788
	SXA	3	0.515	1.421	1.582	0.264	0.737	1.190	1.210

***

= P < 0.001;

= P < 0.01; and

= P < 0.05.

Table 5

Interpopulation variability (coefficient of variation) of leaf morphological traits in field- and garden-grown Hippophae rhamnoides in trans-Himalaya

Parameters	Coefficient of variation
	Male		Female
	Field-grown	Garden-grown	Field-grown	Garden-grown
Leaf Length (mm)	0.19	0.14	0.17	0.13
Leaf width (mm)	0.21	0.15	0.19	0.13
Leaf thickness (mm)	0.17	0.15	0.21	0.11
Petiole Length (mm)	0.26	0.13	0.21	0.15
Leaf Area (cm²)	0.32	0.25	0.29	0.19
Chlorophyll contents (SPAD)	0.12	0.12	0.09	0.18
Specific leaf area (cm²/mg)	0.37	0.33	0.36	0.36

3.2 Genetic differentiation in the common-garden experiment

Altitude of plant origin did not have significant impact on leaf morphology of garden-grown H. rhamnoides (Table 2). No increasing or decreasing trend was observed in leaf length, width, thickness and petiole length with increasing altitude of origin in both the gender. However, a relationship between leaf chlorophyll contents and altitude was observed (R² = 0.37) in males, with lower chlorophyll contents in plants from higher altitude origin. Similar relationship was observed between altitude and SLA of garden-grown male plants (R² = 0.26), with decreasing SLA with increasing altitude of origin (Table 3). However, within each altitude of origin, there was a significant influence of gender on all morphological characters measured. Leaf length, petiole length, leaf area and chlorophyll contents were higher in males than in females (Table 2). SLA was significantly higher in females of all altitude of origin except those from 2800–3000 m asl. However, two-way ANOVA results did not support significant effect of gender on leaf morphology in garden-grown plants (Table 4). A reduced variability in leaf morphology was observed in garden-grown plant as compared to field-grown plant in both the gender (Table 5). However, the exceptions were chlorophyll contents and SLA which remained unchanged in one of the gender. SLA showed opposite trend in field-grown females.

The leaves of the low altitude origin (2800–3300 m) garden-grown plants were smaller in length than those collected from the field in both the gender. However, the opposite trend was observed in plants of higher altitude origin (3500–4200 m). Leaf area of garden-grown male plants was smaller than field-grown plants irrespective of their altitude of origin but the values were not significant at high altitudes. However, the trend was not observed in leaves of female plants. Chlorophyll contents of garden-grown leaves remained higher in males of low altitude origin (2800–3300 m) than field-grown plant. However, a lowering trend was observed in leaves of garden-grown plants of higher altitude origin (3500–4200 m). In contrast, no such increasing or decreasing trend was observed in females. The SLA of garden-grown leaves of male plants was lower than those collected from the field. However, in females the trend was observed only in plants of low altitude origin (2800–3300 m).

4 Discussion

Some of the leaf morphological characters in H. rhamnoides are significantly affected by altitude. Leaf size decreased in both the gender with increasing altitude. This trend is consistent with the findings of previous studies [2 , 11]. Reduction in size is an important strategy employed by plants at high altitude to withstand decrease in temperature and reduced nutrient availability. At high altitude, plants increase supercooling capacity by decreasing cell size and intercellular spaces [17]. Plants decrease the size of their parts to reduce water loss through transpiration, which is a crucial factor in the rain shadowed trans-Himalayan region [11]. Colder soils reduce the water uptake of the root system and induce water stress [18], which might result in reduced size at high altitude. In common-garden experiment, no significant trend was observed in leaf size, suggesting that phenotypic variability along the gradient is due to environmental effect. This trend is consistent with findings of previous studies in other species [2, 10]. In contrast, genetic variation between population from contrasting environments has been reported for leaf size in Populus deltoides and Alchemilla alpina [20], suggesting that diversifying selection with altitude may be responsible for leaf size differentiation. Within each altitude, leaf size was smaller in female than male. Reduced leaf size in females may be due to greater demand for nutrient and carbon for seed and fruit production. Reduced shoot length in females is reported in H. rhamnoides [16]. Garden-grown leaves of low altitude origin (2800–3300 m) were smaller in length than those collected from the field in both the gender. However, the opposite trend was observed in plants from higher altitude origin (3500–4200 m). Our result is in agreement with those of Hovenden and Vander Schoor [10] who reported similar trends in N. cunninghamii. Increase in leaf size of plants of higher altitude origin (3500–4200 m) in garden experiment may be due to more conducive environmental conditions for plant growth at lower altitude. The results elucidate the phenotypic plasticity in response to change in environmental conditions.

Leaf thickness increased with elevation, which is consistent with trends observed in other species along altitudinal gradients [21, 22]. Leaves become thicker with elevation due to increase in intensity of solar radiation and decline in nutrient availability [22]. Increased leaf thickness is an adaptation mechanism against stressful environmental conditions. Leaf thickness is important in terms of carbon assimilation as, so long as light is not limiting, thicker leaves tend to have a higher photosynthetic rate per unit leaf area [12]. Plants from higher altitudes have higher carbon assimilation rates per unit area [13], and there is a genetic basis for this difference [12], which supports the proposition that thicker leaves would be selected for with increasing altitude. Leaf longevity increased with leaf thickness [23, 24] and thus results in an increased residence time of nutrient within the leaves [22], which is beneficial in nutrient-poor environments such as the trans-Himalayan region. Effect of altitudinal gradient on leaf thickness was more prominent in males. Therefore, males are more responsive to change in environmental conditions resulting in greater adaptation. In case of climate change the females are more likely to be adversely affected than males.

We found that there is a decrease in SLA with increasing altitude in both the gender in field-grown plants. The result is consistent with most of the earlier studies [2 , 25], although a study by Schoettle and Rochelle [26] highlighted an increase in SLA with increasing altitude in Pinux flexilis. It has been pointed out that leaves with low SLA generally contain more photosynthetic machinery per unit area [27], increasing water use efficiency and photosynthetic capacity at high altitude [28]. The development of a low SLA is often considered a strategy to increase the longevity of a leaf, in order to optimize the use of scarce nutrients [29, 30]. Our results showed that most leaf morphological variation in H. rhamnoides is environmentally determined, but SLA and leaf thickness are also dependent on genotype. However, environmental influence was stronger than genetic influence (Table 3). This mix of genetic and environmental influences on morphology of H. rhamnoides leaves is also seen in various other species that occur along environmental gradients, including Metrosideros polymorpha [14] and N. cunninghamii [10].

Petiole length in male increased significantly with increasing altitude (R² = 0.44), but similar pattern was not observed in female (R² = 0.04) (Table 3). Elongation of petiole in response to shading is known to increase resource capture under low light condition [31]. However, low light condition alone was an unlikely factor for increased petiole length with increasing altitude in trans-Himalaya. The intensity of solar radiation increases with elevation due to a decline in the optical thickness of the atmosphere [22]. Therefore, the increase in petiole length may be an adaptive response to capture more light to compensate the smaller leaf with increasing altitude. In common-garden experiment, no trend was found for petiole length in both the gender (Table 3), suggesting that this trait is essentially an environmental determinism. The chlorophyll contents differed between ‘high’ and ‘low’ altitudes, with leaves from higher altitude (3500–4200 m) having more than those from lower altitude (2800–3300 m) in both the gender. Increased chlorophyll contents at higher altitude may be an adaptive mechanism to offset the decline in concentration of CO₂ with elevation. Within each altitude, chlorophyll contents was significantly higher in male than female (Table 2), which may be evolutionary advantageous for male for higher photosynthetic activity. Our result is in contrast with that of tropical origin Piper betle, where female contained nearly two fold more chlorophyll than male counterparts [32].

Few studies on tree species [33, 34] have shown that the field-grown phenotypic variability may result partly from the local genetic adaptations of populations over the altitudinal gradient. In our study, it was observed that variation was always greater in field-grown populations than those in the common-garden experiment, indicating the importance of environmental factors. One of the concerns about the potential confounding of genetic and environmental controls of leaf morphology is that the genetic control may mask the climate signals [35]. This would be evident particularly in the long-lived species. This is unlikely to be the case for H. rhamnoides for leaf size characteristics would be useful indicators of environmental conditions.

5 Conclusion

It may be concluded from the results of this study that H. rhamnoides is a prime candidate to investigate gender response to climate change. The morphological variation in leaves of H. rhamnoides is primarily environmentally determined. Our study showed that in the event of climate change the phenotypic plasticity would be a crucial determinant of plant response in mountainous region. Stressful environments will have an added detrimental impact on female than on male. The results elucidated that male will adapt better to the changing climate and may lead to a male-biased population in the event of climate change.

Conflict of interest

The authors have no conflict of interest to report.

Footnotes

Acknowledgments

The study was supported by Defence Research and Development Organisation (DRDO), Ministry of Defence, Government of India. PD and DD are grateful to DRDO for providing Research Fellowship.

References

Nicotra

, Atkin

, Bonser

, Davidson

, Finnegan

, Mathesius

, Poot

, Purugganan

, Richards

, Valladares

, van Kleunen

, Plant phenotypic plasticity in a changing climate. Trends Plant Sci. 2010;15:684–92.

Bresson

, Vitasse

, Kremer

, Delzon

, To what extent is altitudinal variation of functional traits driven by genetic adaptation in European oak and beech? Tree Physiol (2011;31:1164–74.

Kremer

, How well can existing forests withstand climate change?, Climate Change and Forest Genetic Diversity, Implications for Sustainable Forest Management in Europe. Koskela, J , Buck, A , Teissier du Cros, E (eds) Biodiversity International, Rome (2007) pp. 3–17.

Lindner

, Maroschek

, Netherer

, et

, Climate change impacts, adaptive capacity, and vulnerability of European forest ecosystem. For Ecol Manag. 2009;259:698–709.

Sexa

, Cannell

MGR

, Johnsen

, Ryan

, Vourlitis

, Tree and forest functioning in response to global warming. New Phytol. 2001;149:369–99.

Reusch

TBH

, Wood

, Molecular ecology of global change. Mol Ecol. 2007;16:3973–92.

Juvany

, Müller

, Pintó-Marijuan

, Munne-Bosch

, Sex-related differences in lipid peroxidation and photoprotection in Pistacia lentiscus. J Exp Bot. 2014;65:1039–49.

Jones

, Macdonald

, Henry

GHR

, Sex- and habitat-specific responses of a high arctic willow, Salix arctica, to experimental climate change. OIKOS. 1999;87:129–38.

Körner

, Bannister

, Mark

, Altitudinal variation in stomatal conductance, nitrogen content and leaf anatomy in different plant life forms in New Zealand. Oecologia. 1986;69:577–88.

10.

Hovenden

, Vander

Schoor JK

, Nature vs nurture in the leaf morphology of South western beech, Nothofagus cunnighamii (Nothofagaceae). New Phytol. 2003;161:584–94.

11.

Bajpai

, Warghat

, Yadav

, Kant

, Srivastava

, Stobdan

, High phenotypic variation in Morus alba L, along an altitudinal gradient in the Indian trans-Himalaya. J Mt Sci. 2015;12:446–55.

12.

Körner

, Diemer

, Evidence that plants from high altitudes retain their greater photosynthetic efficiency under elevated CO₂. Funct Ecol. 1994;8:58–68.

13.

Hovenden

, Brodribb

, Altitude of origin influences stomatal conductance and therefore maximum assimilation rate in Southern Beech, Nothofagus cunnighamii. Aust J Plant Physiol. 2000;27:451–6.

14.

Cordell

, Goldstein

, Mueller-Dombois

, Webb

, Vitousek

, Physiological and morphological variation in Metrosideros polymorpha, a dominant Hawaiian tree species, along an altitudinal gradient: Role of phenotypic plasticity. Oecologia. 1998;113:188–96.

15.

Williams

, Black

, Phenotypic variation in contrasting temperature environments: Growth and photosynthesis in Pennisetum setaceum from different altitudes on Hawaii. Funct Ecol. 1993;7:623–33.

16.

, Xu

, Zang

, Korpelainen

, Berninger

, Sex-related differences in leaf morphological and physiological responses in Hippophae rhamnoides along an altitudinal gradient. Tree Physiol. 2007;27:399–406.

17.

Goldstein

, Rada

, Azocar

, Cold hardiness and supercooling along an altitudinal gradient in Andean giant rosette species. Oecologia. 1985;68:147–52.

18.

Magnani

, Borghetti

, Interpretation of seasonal changes of xylem embolism and plant hydraulic resistance in Fagus sylvatica. Plant Cell Environ. 1995;18:689–96.

19.

Rowland

, Diversity in physiological and morphological characteristics of four cottonwood (Populus deltoids var. wislizenii) populations in New Mexico: Evidence for genetic component of variation. Can J Forest Res. 2001;31:845–53.

20.

Morecroft

, Woodward

, Experiments on the causes of altitudinal differences in the leaf nutrient contents, size and δ¹³C of Alchemilla alpine. New Phytol. 1996;134:471–9.

21.

Körner

, The nutritional status of plants from high altitudes. Oecologia. 1989;81:379–91.

22.

Roderick

, Berry

, Noble

, A framework for understanding the relationship between environment and vegetation based on the surface area to volume ratio of leaves. Funct Ecol. 2000;14:423–37.

23.

Reich

, Reconciling apparent discrepancies among studies relating life span, structure and function of leaves in contrasting plant life forms and climates: ‘The blind men and the elephant retold’. Funct Ecol. 1993;7:721–5.

24.

Reich

, Walters

, Ellsworth

, From tropics to tundra: Global convergence in plant functioning. PNAS USA. 1997;94:13730–4.

25.

Weg

, Meir

, Grace

, Atkin

, Altitudinal variation in leaf mass per unit area, leaf tissue density and foliar nitrogen and phosphorus content along an Amazon-Andes gradient in Peru. Plant Ecol Divers. 2009;2:243–54.

26.

Schoettle

, Rochelle

, Morphological variation of Pinus flexillis (Pinaceae), a bird-dispersed pine, across a range of elevation. Am J Bot. 2000;87:1797–806.

27.

Vitousek

, Field

, Matson

, Variation in foliar δ¹³C in Hawaïan Metrosideros polymorpha: A case of internal resistance. Oecologia. 1990;84:362–70.

28.

Hultine

, Marshall

, Altitude trends in confer leaf morphology and stable carbon isotope composition. Oecologia. 2000;123:32–40.

29.

Kikuzawa

, A cost-benefit-analysis of leaf habit and leaf longevity of trees and their geographical pattern. Am Nat. 1991;138:1250–63.

30.

Reich

, Walters

, Ellsworth

, Vose

, Volin

, Gresham

, Bowman

, Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: A test across biomes and functional groups. Oecologia. 1998;114:471–82.

31.

Weijschedé

, Antonise

, Caluwe

, Kroon

, Huber

, Effects of cell number and cell size on petiole length variation in a stoloniferous herb. Am J Bot. 2008;95:41–9.

32.

Kumar

, Gupta

, Tripathi

, Gender-specific responses of Piper betle L. to low temperature stress: Changes in chlorophyllase activity. Biol Plantarum. 2006;50:705–8.

33.

Schulze

, Turner

, Nicolle

, Schumacher

, Species differences in carbon isotope ratios, specific leaf area and nitrogen concentrations in leaves of Eucalyptus growing in a common garden compared with along an aridity gradient. Physiol Plantarum. 2006;127:434–44.

34.

Martin

, Asner

, Sack

, Genetic variation in leaf pigment, optical and photosynthetic function among diverse phenotypes of Metrosideros polymorpha grown in a common garden. Oecologia. 2007;151:387–400.

35.

Hovenden

, The influence of temperature and genotype on growth and stomatal morphology of southern beech, Nothofagus cunnighamii (Nothofagaceae). Aust J Bot. 2001;49:427–34.

Gender differences in phenotypic plasticity and adaptive response of Seabuckthorn ( Hippophae rhamnoides L.) along an altitudinal gradient in trans-Himalaya

Abstract

BACKGROUND::

OBJECTIVES:

METHOD:

CONCLUSION:

Keywords

1 Introduction

2 Materials and methods

2.1 Study site

2.3 Statistical analysis

3 Results

3.1 Gender differences in phenotypic variation along altitudinal gradient

Table 2 One way ANOVA in filed grown and common garden grown plants and their difference in different sexes

4 Discussion

5 Conclusion

Conflict of interest

Footnotes

Acknowledgments

References

Table 2
One way ANOVA in filed grown and common garden grown plants and their difference in different sexes