Department of Botany, Acharya Shri Mahapragya Institute of Excellence, Asind, Bhilwara (Raj), India

^*Corresponding author: Sharma V, Department of Botany, Acharya Shri Mahapragya Institute of Excellence, Asind, Bhilwara (Raj), India; E-mail: vinaysharma337@gmail.com

Copyright: © Sharma V. 2022. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Article Information: Submission: 23/08/2022; Accepted: 04/11/2022; Published: 07/11/2022

Rajasthan, the state is situated in the north western part of India and covers as area of 3, 42, 274 sq.km. Despite the hostile climatic conditions of the state, pteridophytes which otherwise known as shade and moisture loving plants. Sitamata wild life sanctuary is located at southwest region of Rajasthan. Different species of pteridophytes in this region exhibit significant variation in thermal stability of their photosynthetic pigments Studies reveal that total chlorophyll contents are maximum in Ceratopteris thallictroides and Selaginella repanda and minimum in Ampelopteris prolifera. The other species range between these two. Total carotenoid contents were found maximum in Cheilanthes bicolor and minimum in Selaginella repanda. These observations suggest that species with greater resistance to drought possess higher quantity of carotenoids and show lesser degradation in their chlorophyll pigments during stress conditions. Thus, Ampelopteris prolifera, Cheilanthes bicolor and Christella dentata are most resistant to heat and drought conditions while A. capillusveneris, Ceratopteris thallictroides and Selaginella repanda are the least resistant taxa to heat and drought conditions.

Thermal stability; photosynthetic pigments; Carotenoids, Chlorophyll content

The dry and hot climate of Rajasthan display abundant growth of pteridophytes from end of July to mid October after which these start to dry up, the photographs of selected fern taxa were shown in Figure 1. Sharma et al. (1977) have established the importance of chlorophyll stability index as an important factor for heat and drought resistance in plants [1]. A higher chlorophyll stability index indicates higher capacity for heat and drought resistance. Studies on photosynthetic pigments shows that total chlorophyll contents are maximum in Ceratopteris thallictroides and Selaginella repanda and minimum in Ampelopteris prolifera. The other species range between these two. Total carotenoid contents were maximum in Cheilanthes bicolor and minimum in Selaginella repanda. These observations support the findings of Rathode and Sharma (1991) who concluded that aquatic and shade loving plants have more amounts of chlorophylls and less of carotenoids while reverse are true in drought resistant types [2]. Analysis of photosynthetic pigments in some pteridophytes was studied in ratnagiri district of Maharashtra suggested that changes were found in amount of chlorophyll pigments during formation of sporangia [3]. Some Physiological studies including photosynthetic pigments like total chlorophylls, carotenoids, polyphenol, major organic and inorganic constituents of pteridophytic flora of Lohgad area of Maharashtra was studied by Gavade et al, ( 2015 ) [4]. The effect of arsenic (As) on photosynthesis of Pteris cretica studied by Zamanova et al, (2021) who reported that increasing doses of Arsenic decreases of net photosynthesis, Transpiration rate and photosynthetic pigments [5].

1gm of fresh leaves of mature plants was homogenized in 15 ml of 80% acetone. After centrifugation, the supernatant was used for quantitative analysis of photosynthetic pigments.Quantitative estimation of chlorophyll a, chl.b, total chlorophylls and total carotenoids was done following the method suggested by Robbelen (1957). Optical densities were recorded at 663 and 645 nm for chlorophylls and at 430 nm for total carotenoid content using a Systronics Spectrophotometer 106 [6]. The Amount of chlorophylls and carotenoids were calculated as per the following formulae:

To determine heat and drought resistance of the selected taxa, thermal treatments of 40°C and 45°C were given to 1 gm fresh leaves in 20 ml distilled water in a water bath for 1h, 2h, 3h and 4h time duration along with controls at room temperature [7]. The leaves were then homogenized in 10 ml of 80% Acetone. Optical densities were recorded at 650 nm and 430 nm respectively.

Total chlorophyll contents and percentage degradation of total chlorophylls and carotenoids were calculated as per the following formulae:

A study of chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids in leaves of mature plants of selected species of pteridophytes occurring in Sitamata wild life sanctuary, Rajasthan has been carried out. Photographs and Data have been presented and Text Figure 1 and in Table 1, respectively.

Treatment of 1-4 hours at 40ºC lead to higher total chlorophyll content degradation in Ceratopteris thallictroides followed by A. capillus-veneris and Selaginella repanda while in Christella dentata, Cheilanthes bicolor and Ampelopteris prolifera it was comparatively low. A temperature treatment of 45ºC for 1-4 hours lead to further loss of total chlorophyll content which was comparatively more in A. capillus-veneris, Ceratopteris thallictroides and Selaginella repanda. These species thus, show more thermal decay in total chlorophyll content compared to Ampelopteris prolifera, Christella dentata and Cheilanthes bicolor.

Ampelopteris prolifera, Cheilanthes bicolor and Christella dentata show maximum degradation of total carotenoids after 4 hours treatment at 45ºC. This percentage of total carotenoid content degradation was recorded to be minimum in Adiantum capillus-veneris, Ceratopteris thallictroides, Ampelopteris prolifera and Selaginella repanda. Maximum percentage of total carotenoid degradation at 40ºC was observed in Cheilanthes bicolor, Ampelopteris prolifera and Christella dentata and it was to be minimum in Adiantum capillus-veneris, Ceratopteris thallictroides, and Selaginella repanda.

Inverse relationship in the degradation pattern of the two different types of photosynthetic pigments namely chlorophylls and carotenoides at higher temperatures is evident in ferns and fern allies of Sitamata forest of Rajasthan. Thermal decay in photosynthetic pigments is a limiting factor for plant growth and supra optimal conditions [8-9]. Bohra et al. (1980) and Yadav & Bhardwaja (1983) concluded that xerophytic species of ferns possess higher carotenoid contents and show lesser degradation of chlorophylls [10-11]. This fits in well with the known functions of the carotenoids-protection of plants from photosensitised oxidation of chlorophyll pigments [12]. The highest chlorophylls were found in gametophyte of Adiantum flabellatum and the highest carotenoids were obtained from the gametophyte of Cheilanthus albomarginata [13]. Distribution and phytochemical studies of some pteridophytes from northern India and Rajasthan state were carried out suggested that species with greater resistance to drought possess higher quantity of carotenoids and show lesser degradation in their chlorophyll pigments during stress conditions [14-15]. Similar observations have been made by Kothari and Yadav (2003). Pareek et al. (2005) and Tripathi et al. (2005) on some ferns and fern allies of Rajasthan [16-18]. Thus, Ampelopteris prolifera, Cheilanthes bicolor and Christella dentata with higher degradation in carotenoids and greater stability in chlorophyll pigments are most resistant to heat and drought conditions while A. capillus-veneris, Ceratopteris thallictroides and Selaginella repanda with higher degradation in chlorophyll pigments are the least resistant taxa to heat and drought conditions.

Total chlorophyll contents among ferns and fern allies were found to be highest in Ceratopteris thallictroides (3.86mg/gfw) and lowest in Ampelopteris prolifera (1.40 mg/gfw). Highest amount of total carotenoids has been observed in Cheilanthes bicolor (0.46 mg/gfw) and lowest in Selaginella repanda (0.13 mg/gfw). These observations suggest that species with greater resistance to drought possess higher quantity of carotenoids. Thus, Cheilanthes bicolor and A. prolifera, which withstand the unfavorable conditions for longer period, contain higher quantity of carotenoids.

Among various metabolic changes underlying the mechanism of heat and drought tolerance of these taxa, mention may now be made of the effect of hyperthermia on total chlorophylls and carotenoids. The data have been presented in Table 2-3. A perusal of Table 2 reveals that different species exhibit significant variations in thermal stability of their photosynthetic pigments. Thus, an hour’s treatment at 40°C led to maximum chlorophyll degradation in Ceratopteris thallictroides (22.37%) followed by A. capillus-veneris with (18.63%), S. repanda (18.13%) and Cheilanthes bicolor it was (9.78%) while the minimum chlorophyll degradation was recorded in Christella dentata (3.62%). However, 4 hour’s treatment at 40°C showed highest degradation of total chlorophyll contents in Adiantum capillusveneris (61.99%) and Ceratopteris thallictroides (61.14%) and the lowest in Ampelopteris prolifera (37.81%). Other species are ranging between these two. A temperature treatment of 45°C for four hours led to further loss of total chlorophyll content which was comparatively more in Adiantum capillus-veneris (75.19%) and Ceratopteris thallictroides (70.60 %). These two texa show more thermal decay in total chlorophyll contents compared to Cheilanthes bicolor (47.00%), Ampelopteris prolifera (47.23%) and Christella dentata (51.11%). Data pertaining to carotenoid contents in response to specified periods of temperature treatment are presented in Table 3. It may be observed from these data that Cheilanthes bicolor (13.51%), Ampelopteris prolifera (11.93%), Christella dentata (9.93%) and Adiantum capillusveneris (9.92%) show higher degradation in carotenoid contents after 1-hour treatment at 40ºC. This percentage of total carotenoid content degradation was recorded to be lower in species of Ceratopteris and Selaginella. Almost similar pattern of carotenoid degradation has been observed at different time duration at 40ºC and 45ºC temperature treatment.

Author is thankful to Dr. B. L.Yadav for his guidance and moral support. I also appreciate Botany department of MLV Govt. College, Bhilwara for providing infrastructure and research facilities.