Morphological characters
Significant differences were observed for growth and yield characters in four genotypes in shade and open conditions.
Effect of Genotypes
The effect of genotypes was significant for leaf area, leaf length, plant height, petiole length and rhizome yield (RY). Plant height was maximum in G3 with 105.67 cm which was on par with G4 (99.00 cm) and lowest in G1 (89.33 cm). Highest leaf length was recorded in G3 (52.00cm) which was on par with G2 and G4 (49.83 cm and 45.17 cm respectively). Lowest leaf length was recorded in G1 (40.75 cm). G4 showed the highest leaf area with 438.00 cm
2 which was on par with G3 (377.67 cm
2) and lowest in G2 (279.83 cm
2). G3 recorded the highest petiole length (27.50 cm) and the lowest in G4 (19.17 cm). G4 with 9.90 kg recorded the highest in RY and the lowest in G1 (3.49 kg) (Table 1).
Effect of shade
The effect on shade showed significant values for plant height, leaf breadth, leaf length, leaf area, petiole length and yield of rhizomes. All the characters under study performed best in shade (S1) in contrast with open (S2) condition. S1 with 122.83 cm emerged highest in the plant heightin contrast with S2 (70.58 cm); Leaf breadth was 11.71 cm in S1 while it is 11.00 cm in S2; Leaf length was highest in S1 (60.13 cm) in contrast with S2 (35.80 cm); Leaf area was the highest in S1 (473.25 cm
2) in contrast with S2 (240.67 cm
2); Petiole length recorded highest in S1 (26.42 cm) while it was 19.42 cm in S2 condition and RY was highest in S1 (8.79 Kg) in contrast with 2.79 Kg in Open condition (Table 1).
Interaction effect of genotypes and shade
The interaction effect of genotype and shade condition showed significant result in leaf area and rhizome yield. Highest leaf area was recorded in G4S1 (634.33 cm
2) and the lowest in G1S2 (221.33 cm
2). G4S1 (16.27 kg) recorded the highest rhizome yield and the lowest in G1S2 (1.90 kg) (Table 1).
Srikrishnah et al. (2012) also recorded significant higher leaf area, biomass and yield in shades of 50% and 70% in contrast with the 0% shade levels in 3 varieties of
Dracaena sanderiana L. The different varieties of ginger performed better in terms of morphological and yield characters and rhizome yield under shade conditions in contrast with the open conditions
(Babu et al., 2019). The increase in fresh weight of rhizome might be attributed to higher photosynthetic activity under favourable soil temperature, low light intensity and higher relative humidity under shade net condition. The increased in plant height, leaf sizes, leaf area per plant might eventually affect the rhizomes characters which resulted in a higher yield of rhizome in shade condition in contrast with plants grown in open conditions. Generally, the growth response of plants in shade might also be strictly depended on genotype and thus is species-specific
(Fini et al., 2010). M. melissophyllum, which a typical shade loving plant when grown in direct sunlight produced more number of shoots than those grown in shade. The shoots were shorter and the leaf area was smaller than those plants grown in shade condition
(Sandhu et al., 2020). When a plant is subjected to acclimatize to inhospitable conditions, the structure and diameters of the leaves may change
(Anderson et al., 1991; Cai et al., 2007; Van Hees et al., 2003). Typically, when grown in deep shade, the leaf area expands to enhance light absorption, while its thickness and mass per unit decrease
(Hirano et al., 2019). Budiastuti et al. (2022) also reported highest number of leaves, fresh plant weight and total biomass in
Indigofera tinctoria L. were observed under the shading treatment applied during the early growth stage (up to one month after planting) at 50% light intensity. Maximum indican production, reaching 843.33 ppm, was recorded under mid growth shading (up to two months after planting) at 10% light intensity. Thus the result in our experiment indicated the effect of genotype and shade conditions on the growth and yield of the plants.
Chemical constituents
GCMS analysis was done for the samples collected from the genotypes grown under shade and open detected. Results indicated a quite difference in the chemical content among the genotypes and between the same genotype grown under shade and open conditions. The expression of compounds in shade and open conditions vary in numbers and types and also amongst the genotypes the expressions of compounds were different. Those compounds which were expressed commonly in shade and open conditions were compared. In G1, a total number of 52 commonly expressed compounds were analysed and their peaks were compared (Fig 3). In G2, a total number of 34 commonly expressed compounds were analysed and their peaks were compared (Fig 4). In G3, a total number of 38 commonly expressed compounds were analysed and their peak heights were compared (Fig 5). In G4, a total number of 32 commonly expressed compounds were analysed and their peaks were compared (Fig 6).
A total of 18 compounds were identified which were expressed commonly in all the genotypes grown under shade and dry conditions. The commonly expressed compounds were Heptadecane, Lyxose,O,O,O,O-TMS MEOX1, Piperidine hydrochloride, Ribitol TMS, Myo-Inositol, 6TMS derivative, Iron, tricarbonyl [N-(phenyl-2-pyridinylmethylene)benzenamine-N,N’]-,Epicurzerenone,Benzofuran,6-ethenyl-4,5,6,7-tetrahydro-3,6-dimethy l-5-isopropenyl-, trans-Hexanol-4-D2, Trehalose TMS, Phosphonic acid, dioctadecyl ester, Palmitic Acid, TMS derivative, Stearic acid, TMS derivative, 3,4-Pentadien-2-d-1-ol, Octyl (t-Butyl) Carbonate, trans-2-methyl-4-n-pentylthiane, S,S-dioxide,2,3-Dimethylthiirane 1,1-dioxide, .beta.-Vetivenene. The various peak comparisons of these compounds are given in (Fig 7).
The bioproduction of terpenoids in plants is closely linked to light conditions and both ultraviolet (UV) and regular light serve as significant triggers for terpenoid synthesis (
Zhang and Bjorn, 2009;
Kawoosa et al., 2010; Xie et al., 2021). Among various light forms, UV-B is found to enhance terpenoid accumulation in many plant species (
Takshak and Agrawal, 2019). Phenolic accumulation in plants is influenced by several factors, with genotype, ontogeny and environmental conditions related to biotic and abiotic factors being the most critical (
Verma and Shukla, 2015). It has been demonstrated that shading reduces the concentration of phenolics and alters their composition in the berry skins of
Vitis vinifera cv. Cabernet Sauvignon
(Koyama et al., 2012). Therefore, light levels may be an effective tool for modifying the chemical profile in plants. In many species, higher doses of photosynthetically active radiation (PAR), within the 400-700 nm range, have been shown to stimulate the synthesis of flavonoids and hydroxycinnamic acids. This effect has been particularly well-documented in shade-loving plants such as bilberry,
Mikania laevigata Sch. Bip. ex Baker and
Mikania glomerata Spreng. Additionally, it has been reported that the coumarin content in the leaves of
M. laevigata increases with the level of shade
(Bertolucci et al., 2013). A similar trend was observed in
Hierochloe australis (Schrad.) Roem. et Schult. (
Bączek et al., 2019). Both species are typical undergrowth plants, found in semi-shaded environments where the coumarin accumulation varies under different light conditions.
Principal component analysis (PCA)
Principal component analysis was carried out separately for the four genotypes (G1, G2, G3 and G4) grown under shade and open conditions.
The experimental dataset consists of 2 treatment combinations for 52 respective variables (Compounds expressed under GCMS) for G1 genotypes in the analysis. Analysis was conducted with all 52 variables together and the loadings plot and the component matrix were used to interpret the dataset. The loading plot shows the correlationwith principal component and the original variables. Principal components i and ii account for 86.83% and 13.16 %, respectively, of the total variation in the dataset, so the two-dimensional loading plot of the data set given in the figure is an excellent approximation to the original scatter-plot in two-dimensional space. Among all the loadings, Mannose MEOX TMS, Lyxose, O,O,O,O-TMS MEOX1 and Sucrose TMS has contributed majorly under PC
1 while Mannose MEOX TMS, Palmitic Acid, TMS derivative and Ribitol TMS has contributed majorly under PC
2 (Fig 8a).
For the genotype G2, the experimental dataset consists of 2 treatment combinations for 34 respective variables (Compounds expressed under GCMS) in the analysis. All the 34 variables together and the loadings plot and the component matrix were used to interpret the dataset. The loading plot shows the correlation with the principal components and the original variables. Principal components I and II account for 91.89% and 8.11 % of the total variation in the dataset, so the two-dimensional loading plot of the data set given in the figure is an excellent approximation to the original scatter plot in two-dimensional space. Among all the loadings, Palmitic Acid, TMS derivative, Epicurzerenone and Sorbtol TMS has contributed majorly under PC
1 while Lyxose,O,O,O,O-TMS MEOX1, Mannose MEOX TMS, Sorbtol TMS has contributed majorly under PC
2 (Fig 8b).
The experimental dataset consists of 2 treatment combinations for 38 respective variables (Compounds expressed under GCMS) for G3 genotypes in the analysis. All the 38 variables together and the loadings plot and the component matrix were used to interpret the dataset. The loading plot shows the correlation with principal components and the original variables. Principal components I and II account for 91.36% and 8.63 %, respectively, of the total variation in the dataset, so the two-dimensional loading plot of the data set given in the figure is an excellent approximation to the original scatter-plot in two-dimensional space. Among all the loadings, Mannose MEOX TMS, Lyxose,O,O,O,O-TMS MEOX1 and Sucrose TMS has contributed majorly under PC
1 while Palmitic Acid, TMS derivative, Epicurzerenone, Mannose MEOX TMS has contributed majorly under PC
2 (Fig 8c).
The dataset of G4 consists of 2 treatment combinations for 32 respective variables (Compounds expressed under GCMS) in the analysis. All the 32 variables together and the loadings plot and the component matrix were used to interpret the dataset. The loading plot shows the correlation with principal components and the original variables. Principal components I and II account for 94.86 % and 5.13 %, respectively, of the total variation in the dataset, so the two-dimensional loading plot of the data set in the figure is a remarkable approximation to the original scatter-plot in two-dimensional space. Among all the loadings, Palmitic Acid, TMS derivative, Epicurzerenone and Sorbtol TMS has contributed majorly under PC
1 while Lyxose,O,O,O,O-TMS MEOX1, Mannose MEOX TMS, Palmitic Acid, TMS derivative has contributed majorly under PC
2 (Fig 8d).