Impact of habitat variability and altitude on growth dynamics and reproductive allocation in Ferula jaeschkeana Vatke

2.1 Study sites

F. jaeschkeana was found growing in Daara, Dachigam, Betab valley – Pahalgam, Chandanwari, Gulmarg, Aharbal, Jawahar tunnel, Ferozpora, Drang, Narayanag, Daksum, Kokernag and Drass. Four natural populations (Dachigam, Drang, Betab valley – Pahalgam and Gulmarg) and one transplanted control population grown at KUBG (Kashmir University Botanical Garden) were selected for the present study (Fig. 1). The origin of plants growing at KUBG is not known and has been collected earlier from natural habitats. The salient features of the selected sites are depicted in Table 1.

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Figure 1

Map showing the location of study sites of Ferula jaeschkeana in Kashmir Valley.

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2.2 Morphological characterization

The studies were carried out in both ex situ as well as in natural habitats and photographs were taken using Canon A810 camera. Ten mature flowering individuals were selected randomly and tagged from each population in order to observe the various morphological parameters of the species and to record the variability in floral and vegetative traits. The populations were analyzed for morphological traits like number of shoots per plant, root tuber dimensions, plant height, basal leaf length, pinnae number, pinnae length, pinnule length, number of flowering stems per plant, flowering stem length, sheath number per plant, sheath length, number of umbels, umbel diameter, umbels per flowering stem, umbellule’s per umbel, number of flowers, fruit morphology and fruit number. The plants were measured in situ and most of these parameters were recorded at flowering stage in all the populations. We used linear regression analysis to determine the correlation between various morphological parameters across the altitudinal gradient so as to find the sites of better growth performance of this species. Principal component analysis (PCA) was carried out to analyze the morphological traits in relation to habitat dynamics. In addition to this, it was also used to infer the coherence between different vegetative and reproductive parameters.

2.3 Reproductive success

The umbels were dissected under the stereo zoom microscope (Zeiss Discovery. V8) and the number of flowers per umbellule were counted to examine the proportion of variation within and among plants as well as among populations. The mature umbels containing mericarps were collected from all the selected populations. We determined the percentage seed set of each plant expressed as the ratio of developed fruits to the total number of flowers.

2.4 Reproductive allocation

Fifteen mature and healthy flowering plants from all the natural populations were harvested for the study of resource partitioning in different parts of a plant. The plants were fragmented into individual parts such as root tubers, leaves, stem and inflorescence. Using an electronic balance, fresh weight (weighing as fresh) and dry weight (after oven-drying for 48 h at 80 °C) of the plants were determined following Kawano and Masuda (1980). Reproductive effort (RE) was calculated from the estimates of dry weight or biomass allocated to reproductive and vegetative structures (Abrahamson and Gadgil, 1973): $$\text{RE}=\frac{\text{Dry weight of inflorescence}(\text{including stems})}{\text{Total dry weight of the above and below ground parts}}\times 100$$

2.5 Data analysis

ANOVA was used to test for differences between populations for all the morphological characters measured using the SPSS 16.0 software. Tukey’s multiple comparison of means was used to compare all populations and the differences between individual means were deemed to be significant at p ⩽ 0.05.

3.1 Growth characteristics

Present investigation revealed a wide range of suitable habitats for the growth of F. jaeschkeana (Fig. 2). The species prefers to grow in the shady plains, rocky open slopes and open slopes with loose textured soils (Table 1). F. jaeschkeana is a herbaceous perennial plant with 1–2.5 m tall solitary, thick, reddish brown stem and a huge woody taproot, that grows 19–22 cm deep below the soil surface. The stem base is clothed in fibrous remnant sheaths. Upper leaves are reduced to large sheaths often with umbels in their ascils.

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Figure 2

Different types of habitats of Ferula jaeschkeana in Kashmir Valley. (A) Open plains; (B) shady slope; (C) mountainous slope; (D) open slopes with loose textured soils.

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At both inter and intra-population levels, the species exhibits a considerable variability in its morphological traits under different environmental conditions (Table 2). Highly significant differences among populations were observed in plant height, leaf dimensions, umbel size and umbellule number. The main difference between the populations was obvious in the plant height which was almost double in plants growing at low altitude sites KUBG and Dachigam (210.05 ± 17.42 cm and 197.61 ± 13.15) than in Gulmarg (106.17 ± 27.17). The flowering stem length and basal leaf length were also highest (35.05 ± 6.52 and 108.45 ± 18.56 cm, respectively) at low altitude KUBG and were the least (26.16 ± 4.77 and 74.93 ± 10.03 cm, respectively) at Gulmarg. Besides, the pinnae number per plant, pinnae length and pinnule length were also maximum (5.2 ± 1.47, 58.92 ± 10.54 cm and 17.52 ± 3.47 cm, respectively) in the plants of low altitude site, KUBG and were minimum (2.2 ± 0.5, 33.52 ± 7.87 and 7.36 ± 2.13) in the plants of high altitude site, Gulmarg. The root tuber length and root tuber breadth followed the same trend and ranged from 19.3 to 22.86 cm and 10.66 to 15.49 cm, respectively.

Plants flowered for a period of 7–9 weeks and the highest percentage of flowering plants was recorded between May and early-June. Transplanted population at KUBG showed the highest values of almost all the morphological traits as compared to the natural populations. An increase in the number of stigma and anthers was also observed in some plants (Fig. 3) growing at the Betab valley – Pahalgam and Gulmarg. A positive correlation between root tuber length and plant height (r² = 0.1459), plant height and basal leaf length (r² = 0.3497), plant height and umbel diameter (r² = 0.2843), umbellules per umbel and flowers per umbellule (r² = 0.396), number of ramets and umbellules per umbel (r² = 0.1287) and number of ramets and flowering stems per plant (r² = 0.0734) was observed (Fig. 4).

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Figure 3

Increase in the number of stigma and anthers of flowers. (A) Gynoecium with three stigmas and styles; (B) gynoecium with four stigmas and styles; (C) flower with six anthers; (D) flower with seven anthers.

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Figure 4

(A–F) Regression analysis between several morphological characters of F. jaeschkeana.

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Principal component analysis (PCA, Fig. 5) of all morphological characters across the study sites reveals that the major differences between populations were due to size characteristics (axis 1; 85% of total variance) and separated KUBG and Dachigam (with high character values) from the other populations. PCA reveal that the high altitude populations are non-favorable to most of the vegetative and reproductive traits indicating better growth conditions at lower altitudes. Flowering stem length, root tuber length (cm), number of ramets, umbel diameter, pinnae number, pinnae length, and pinnule length were found to be favoring KUBG population. Basal leaf length, number of flowering stems per plant, sheath length, umbels per flowering stem, umbellules per umbel, plant height, root tuber breadth (cm), flowers per umbellule, and sheath number per plant were found to be favoring the Dachigam population. Thus, the habitat of KUBG and Dachigam proved relatively better for the growth of F. jaeschkeana.

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Figure 5

Principal component analysis (PCA) of morphological characteristics of Ferula jaeschkeana across the different study sites. LL – basal leaf length, NFS – number of flowering stems per plant, SL – sheath length, UFS – umbels per flowering stem, UPU – umbellules per umbel, PH – plant height, RTB – root tuber breadth (cm), FPU – flowers per umbellule, SN – sheath number per plant, PN – pinnae number, PL – pinnae length, NR – number of ramets, FSL – flowering stem length, UD – umbel diameter, PIL – pinnule length, RTL – root tuber length (cm).

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3.2 Reproductive success

With increased altitude, a significant reduction in the number of umbels per flowering stem, umbellules per umbel and flowers per umbellule occurred (Table 2). Percentage seed set of the plant species also varied along the altitudinal gradient and ranged from 64% to 72%. The number of umbellule per umbel varied with overall plant height from 5 to 7 across populations. Moreover, the number of ramets per root tuber varied from 1 to 4 which represents a copious variation in numbers of umbellules per umbel, umbels per flowering stem, number of umbels and thus the reproductive success.

3.3 Reproductive allocation at flowering

It is evident from the data (Table 3) that partitioning of resources is not uniform among different parts of a plant. A striking difference was observed in total above ground dry weight and dry weight of different vegetative structures among the plants of studied populations, growing at different altitudes. The total resource budget per plant and the above ground dry weight of low altitude populations (Drang and Dachigam) and high altitude population (Gulmarg) varied to a greater extent. The values were maximum in low altitude Drang (572.6 ± 158.36 g and 407.2 ± 123.5 g, respectively) and Dachigam (568.4 ± 133.42 g and 359.6 ± 104.97 g, respectively) populations and were least in the Gulmarg population (333.4 ± 82.89 g and 236.8 ± 56.18 g, respectively). Also the percentage allocation to reproductive parts, i.e., reproductive effort was more (50.83) for the high altitude Gulmarg population. Maximum resources were allocated toward the growth and development of stem (156.9 ± 62.24 g to 275.3 ± 85.18 g) followed by root tuber (96.6 ± 26.71 g to 208.8 ± 28.45 g) and leaves (67.3 ± 10.19 g to 112.5 ± 35.69 g) while the least resources were allocated toward inflorescence (12 ± 3.12 g to 19.4 ± 2.63 g).