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Author: Hawa Singh × End date: 2006 × Start date: 2002 × Type: Thesis ×
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    ThesisItemOpen Access
    Physiological responses of chandrashura (lepidium sativum L.) to salt stress
    (CCSHAU, 2004) Hawa Singh; Varshney, U.K.
    Chandrashura (Lepidium sativum L.) is a crop of medicinal importance which is being cultivated in the arid and semi-arid regions of different states like Gujrat, M.P., Rajasthan, U.P., Maharastra and to some extent in Haryana also as a rabi crop where it is influenced by salt/water stress. The present research deals with the physiological responses of Chandrashura to salt stress. The effects of salts that chiefly contribute to soil salinity viz. NaCl and Na2SO4, singly as well as in combination were studied on seed germination, seedling growth, plant water relations, growth and development; biochemical as well as minerals constituents and yield attributes. To achieve the objectives of the research problem two experiments were planned.First experiment was conducted in the controlled conditions of a culture room with 25±1ºC temperature and 16h light, 8h dark period. The experiment was performed in petri dishes using three salt treatments viz. NaCl, Na2SO4 and NaCl + Na2SO4 (1:1 meq/l basis) with varying EC levels viz. O (control), 4,8,12,14,16, 18, 20, 22, 24 and 26 dSm-1. Results revealed that the progressive increase of EC levels not only inhibited the seed germination but also declined the speed of germination (maguire index). Effective delay in germination was more pronounced under Na2SO4 among all the salt treatments at higher EC levels. All the three salt treatments were proved deleterious to Chandrashura seedlings as they decreased the seedling length, vigour index, fresh and dry weights of root and shoot. Na2SO4 treatment in this regard was found most detrimental to seedlings followed by combined salt treatment and then NaCl treatment. The above salt treatments also reduced the relative water content in shoot of seedlings with increase of EC levels. Na2SO4 treatment was found more effective in reducing RWC at low EC levels than NaCl treatment. Maximum increase of membrane permeability index under Na2SO4 treatment while minimum under NaCl treatment indicated more toxicity of the former on plasma membrane. In the second experiment, plants were raised in polythene bags with sieved dune sand in screen house at varying EC levels viz. 0 (Control), 4, 6, 8, 10, 12, 14 dSm-1 of NaCl, Na2SO4 and NaCl+Na2SO4 (1:1 meq/l basis) along with nutrients. Salt stress in general adversely affected the various growth and developmental parameters viz. plant height, number of leaves per plant, number of branches per plant, root volume, root and shoot dry weight, total plant dry weight, root and shoot ratio. Among the three salt treatments, NaCl proved most deleterious while Na2SO4 least deleterious to Chandrashura with regard to above parameters. Significant changes in various biochemicals were also recorded. Total soluble carbohydrates as well as proline accumulated under increasing stress conditions created by the salts. The accumulation of these organic solutes in different plant organs helped plants in osmotic adjustment under salt stress. Ascorbic acid, chl ‘a’, chl ‘b’, total chlorophyll contents undergone more reduction under NaCl treatment than under Na2SO4 treatment. Ascorbic acid content was in general higher in top leaves of plants. Na+, Cl- and SO42- contents of shoot increased while K+ content decreased with increasing EC levels. Accumulation of Na+ and Cl- was more under NaCl treatment while that of SO42- was higher under Na2SO4 treatment. Slight postponement in number of days to flower initiation and preponement in crop maturity was found with increasing EC levels. All the three salt treatments caused significant reduction in the number of fruits per plant, 100 seed weight and the seed yield per plant with the increase of EC levels. The NaCl treatment in this regard was more reducing then Na2SO4 treatment and caused more than 50% reduction in seed yield beyond 12 dSm-1 EC level. The response of NaCl and Na2SO4 salt treatments was contrary at germination-early seedling growth and later plant growth stages. NaCl was relatively less deleterious at germination and early seedling growth stages but found more toxic at the later plant growth stages than Na2SO4.