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PHOTOSYNTHATE PARTITIONING IN WHEAT (TRITICUM AESTIVUM L.) AS AFFECTED BY ROOT-ZONE SALINITY AND FORM OF N

ASMA LODHI^1*, MUZAFFAR HUSSAIN SAJJAD¹, ANSAR MAHMOOD¹, SHERMEEN TAHIR¹ AND FAROOQ-E-AZAM²

Abstract: Carbon-14 pulse labeling technique was used to study the effect of rooting medium salinity and form and availability of N on growth and rhizodeposition of wheat (Triticum aestivum L.). Of the applied ¹⁴C pulse, 83% was determined in plants, while 89% and 11% was determined in the shoot and root portions, respectively. Salinity showed a depressing effect on different plant parameters particularly on roots. However, NO₃^--fed plants showed better growth than NH₄⁺-fed plants at all the three salinity levels. Presence of NaCl in the rooting medium led to a decrease in the water content of both root and shoot portions. The proportion of assimilated ¹⁴C released into the rooting medium as rhizodeposits varied between 1.5 and 3.2%, while 8-13% was unaccounted for and assumed to be respired. Rooting medium salinity led to higher rhizodeposition and lower loss of ¹⁴C. Relatively higher proportion of ¹⁴C was released as rhizodeposits and retained in root and shoot portions of plants fed with NH₄⁺ or NH₄⁺+ NO₃^- than those with NO₃^- while less was respired. The specific activity of the rhizodeposits was also higher under saline conditions. The rhizodeposits in NH₄⁺-fed plants were more highly labeled as compared to NO₃^--fed plants.
 

¹Nuclear Institute for Agriculture and Biology (NIAB), P.O. Box 128, Jhang Road, Faisalabad, Pakistan

²Nuclear Institute for Food and Agriculture (NIFP), Peshawar, Pakistan

^*Corresponding author E-mail: alv51062@yahoo.com