PJB-2009-147
PHOTOSYNTHATE PARTITIONING IN WHEAT (TRITICUM AESTIVUM L.) AS AFFECTED BY ROOT-ZONE SALINITY AND FORM OF N
ASMA LODHI1*, 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.
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