Stem internodes reserves and mobilization of barley genotypes during grain filling under terminal drought.

Stem reserves of barley can be an important contributor to grain filling particularly under conditions when assimilation is limited such as during end-of-season drought. A divers set of spring two-rowed and six-rowed barley (Hordeum vulgare L.) with different origins and heights were grown in a field trial where water availability was manipulated. Dry matter (DM) related traits were monitored. Drought on average reduced maximum weight of peduncle penultimate and lower internodes by 13% 12% and 8% and reduced their minimum weight by 18% 9% and 10% respectively which in turn increased the mobilized dry matter (MDM) by 5% in peduncle and lowered that of the penultimate and lower internodes by 27% and 5% respectively. Conclusively an increase of 31% and 13% and a decrease of 10% were observed with regard to remobilization efficiency (RE) of peduncle lower internodes and penultimate respectively. Drought on average reduced postanthesis maximum and minimum weight of stem by 9% and 11% respectively also reduced MDM by 5%. Conclusively an increase of 13% was observed with regard to dry matter RE of stem. No relationship was found between MDM and stem length in both well-watered and drought treatments whereas there was significant correlation between internodes and stem MDM and their specific weight. Yield of main spike showed 24 percent decrease by entering drought conditions. Contribution of stem reserves in the yield of main spike increased by 33% under drought conditions and didn’t show any significant correlations with maximum weight and length of stem in none of moisture treatments.