This study investigates the response of two wheat
cultivars to boron toxicity stress. Plants were
cultivated in sand culture and boron was applied to
the culture for 10-day. Symptoms, tiller number,
boron concentration, soluble sugars, proteins and
other free amino acids than proline were studied.
The differences between the cultivars were apparent
from higher boron and the chlorosis in tolerant
cultivar was about 7% compared to the sensitive one
70%. Tiller number gradual decreased in tolerantcultivar,
while in sensitive one a dramatic reduction
was exhibited by increasing boron level in culture
media. In most boron levels, although the accumulation
of soluble carbohydrates was significantly
stimulated in shoot of B-sensitive cultivar
(Gemmeza 9; S), there were no appreciable
differences in the production of carbohydrates in
shoot of B-tolerant cultivar (Sakha 93; T). However,
the soluble proteins production did not affect by
most boron levels in both cultivars. The presence
of boron at various concentrations induced a
production of free amino acids in shoots of each of
the two test cultivars. Tiller number (yield index)
decreased in the two test cultivars and was in range
50-59 and 84-92% less than control plants for
tolerant and sensitive cultivar, respectively.