| dc.description.abstract | Variation of growth and salt tolerance was studied at increasing external salinity in sevenseed
provenances of Acacia tortilis from saline (Sigor, Katilu, Mwatate and Isiolo) and nonsaline
(Kibwezi, Wamba and Kitui) regions of Kenya and under stable saline conditions in
Kitui, Isiolo and Mwatate provenances. The traits that may help provenances adapt to saline
environments were more conspicuous in saline provenances. These were: (i) higher biomass
production with and without salt treatment, except Isiolo provenance, (ii) maintaining low shoot
Na concentration, (iii) greater leaf Na tolerance and (iv) more responsiveness to salt stress,
suggested by the salt-induced growth reduction and leaf-fall. While these adaptations were not
universally distributed among saline provenances, all provenances possessed one or more of these
adaptations. Seedling survival was not related to putative salinity of sites. However, the high
survival rates and low shoot Na concentration of Sigor, suggests that Na exclusion could have
promoted longer-term survival of this Acacia tortilis provenance.
Other elements (K, Ca, Mg and N) were not consistently correlated with salinity of seed
origins, suggesting that mineral nutrient levels responded to diverse plant and salt stress variables,
including seedling age and organ, and salt application methods (increasing or stable). However,
canonical analysis revealed that interactions among nutrients could have been site dependent. This
technique separated provenances, both within and between site categories, using concentrations
of shoot Na, root Ca and root Mg. Ecotypes may have differentiated based on varied mechanisms
of ion balances, which evolved differently depending on edaphic conditions. The study suggests
that use of saline provenances may also increase biomass production in non-saline regions of
Kenya. | en |
