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Title: Role of Root Applied Ascorbic Acid in Modulating Physiological and Molecular Responses Salt Stressed Maize
Authors: Saleem, Asma
Keywords: Botany
Issue Date: 2017
Publisher: University of Agriculture, Faisalabad.
Abstract: Salinity is a major debacle to plants growth and roots are the first target to its toxicity. Ascorbic acid (AsA) is a widely distributed compound in plants and performs crucial and protective roles including cell division, cell elongation, wall expansion, control from photodamage and a variety of cellular and whole plant processes. The mitigation role of multifunctional AsA to salt stressed roots of maize (Zea mays L.) was determined. Five levels of salt stress (40, 80, 120, 160 and 200 mM NaCl), and of AsA (0, 1, 1.5, 2, 2.5 and 3 mM) were optimized. High level of salinity (160 and 200 mM) affected growth attributes of all five maize hybrids, while all AsA levels promoted maize growth. Shoot and root length as well as fresh and dry weight of all five maize hybrids increased with increase in AsA levels. Depending upon the response of maize hybrids, 32B33 was selected as tolerant and 30Y87 as sensitive one. AsA level of 2.5 mM and salinity level of 120 mM NaCl were optimized for interaction studies on stele and sleeve tissues of two selected maize hybrids. After the selection of appropriate levels of salinity and AsA, the detailed experiments were performed to determine the mechanism of AsA action in improving salinity tolerance in maize. Results revealed that AsA alone enhanced shoot and root length, fresh and dry weight more in tolerant hybrid (32B33) and AsA in combination with NaCl (120 mM) also increased shoot and root water contents in both the hybrids. Salinity damaged the stele and sleeve architecture of root while AsA decreased the cortical layers, increase cortical cells size, while number of metaxylem cells increased with no damage to wall properties of 32B33 as compared to 30Y87 (medium sensitive). Similar results were found in the studies conducted at UC Davis, USA on the primary and nodal roots of these hybrids. The damage caused to sleeve and stele tissue of 30Y87 were due to high production of H2O2, MDA, reduced reduced soluble sugars, free proline, glycine betaine, soluble proteins and vitamins (riboflavin, niacin and thiamine) while the scenario was otherwise in case of treatment with AsA alone or in combination with salinity. AsA lowered the concentration of Na+ in the stele and sleeve while K+, N, P and S contents were improved in the presence of AsA in salt treated roots. In conclusion, sleeve was more prone to damage by salinity as compared to stele part of root and AsA was quite effective in enhancing the growth and physiological activities in sleeve and stele irrespective of the salinity applied.
Gov't Doc #: 16920
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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