Abstract

INTERACTION BETWEEN HEMIPARASITIC- DENDROPHTHOE FALCATA (L.) ETTING. ON MANGIFERA INDICA LINN. – SOME OBSERVATIONS

Pradeep DP, Meenu Krishnan VG, Aswathy JM, Greeshma M, Greeshma GM, Remya Krishnan, Lubaina AS & Murugan K*

ABSTRACT

Dendrophthoe, a perennial flowering plant, face several interesting physiological challenges. It is an evergreen, sturdy, hemiparasite belongs to Loranthaceae, distributed in the tropical and sub-tropical regions of the world. An attempt was made to unravel the physiological and biochemical defense of mango plant (host) against the invasion of the parasite Dendrophthoe falcata (L.) Etting. The methodologies adapted include microscopic, analytical and biochemical. Chlorophyll pigments showed a decrease possibly the reduction in availability of water and minerals. Reduction in soluble sugar contents was noted in the infected mango plant by the parasite. Significant increase in amino acids content was observed. Proline, a stress amino acid also increased during parasite invasion. Alpha amylase activity showed a higher profile corroborating with the sugar content. Total phenols also showed a reduction substantiated by localization studies meanwhile, flavonoids displayed an increased profile. Parasite invasion created an oxidative stress environment in the host tissue by producing the superoxide anion radical and hydrogen peroxide. Phenolic acids also showed variation among the plants corroborating with phenolic content. Elevated level of hydrogen peroxidase in the infected mango suggests the oxidative stress in the plant. Infected host tissue showed a preliminary defense strategy by inducing its antioxidant machinery of enzymes and compounds. The activities of total superoxide dismutases (SODs) as well as ascorbate peroxidase (APX) showed consistent increases with stress, however catalase activity declined. Biotic stressed mango plants also had higher guaiacol peroxidase (GPX) activity than control plants. Poyphenol oxidase (PPO) and phenols showed a negative correlation i.e., high PPO activity and low phenol content. The present data confirms the biotic stress induction of oxidative stress in the plants by analyzing the primary antioxidant enzyme SOD and the key enzyme APX of ascorbate-glutathione cycle. Meanwhile, catalase showed a low profile indicating its non involvement in scavenging hydrogen peroxide. Similarly, the higher profile of phenylalanine ammonialyase (PAL) is another positive response shown by the infected plants suggests the active phase of the plant in the synthesis of secondary metabolites. The activity of the enzyme supports the polyphenol content in the plant. Leaf IR reflectance spectra 4000–450/cm of Mangifera indica infected with the parasite – Dendrophthoe falcata were recorded with a Fourier Transform – Infrared (FTIR) and analyzed for parasite invasion-specific spectral signatures. Several indicator bands that are pertained to functional groups represent chemical components or metabolic products. No absorption bands were common among infected and control suggesting the FT-IR finger print are unique in plants. The pronounced peaks belonging to vibration of C=O, C–OH, C–N, and N–H were present in the spectra of diseased leaves indicating the presence of proteins, amino acids, carbohydrates, amides or phenols. Protein banding pattern also showed sound variation in the infected plants supporting its assay data.

Keywords: Alpha amylase, Ascorbate peroxidase, Catalase, Dendrophthoe falcate, Guaiacol peroxidase, Haustoria, Mango, Parasitism, Phenols, Phenylalanine ammonialyase, Superoxide dismutase.