The role of Znic in alleviating B-toxicity in plants differing in their sensitivity to boron in terms of rooting response of cuttings.

Abstract

The role of Znic in alleviating B-toxicity in terms of adventitious root formation (ART) in cutting of plants differing in their sensitivity to boron such as Mung bean (sensitive ) ,Cucumber (Moderately tolerant ) and Tomato (tolerant ) has been carried out . The toxic level of B  in addition ,to the promontory  conc. Of Zn-salt was determined for each of the  above spp. Three of Zn-salts were tested ( sulphate ,nitrate and chloride ) and the best promontory salt is Znic sulfate in developing the higher number. of roots in addition to the best conc. of the same salt was 15,10,15 pmm for Mung bean , Cucumber and Tomato respectively ,comparing to other Zn-salt & their concentration .

The toxic levels of boron was 200,300 and 400 µg/ml for Mung bean , Cucumber and Tomato respectively . These levels reduced growth parameters in terms of  rooting response to 50% or beyond (55.16% ,50.83% and 53.49% )for Mung bean , Cucumber and Tomato compared to control in addition ,to the localized toxic symptoms like necrotic spots at leaves edges of the a above 3- spp. respectively .

Boron detoxification was occurred completely by supplying Znic  sulphate prior to toxic–B treatment (pre-treatment )in all spp. compared to its supply as post- treatment or simultaneously with    toxic –B . The protective role of Znic – sulphate was significantly enhances the average of root number /cutting to its levels in control treatment  ( in absence of toxic – B)in all spp. under study .

Toxic levels of B for the above spp. were caused  significant damage for plasma- membrane of leaf tissues via permeability perturbation in terms of EC% with increasing 111.05%, 50.015%  and30.65 in cutting  of Mung bean , Cucumber and Tomato respectively . Whereas ,in seedling (in presence of root system ) the % of damage was declined to 83.74%,42.59% and 9.91% when exposed to B-toxicity .These results confirms the sequostration mechanism of boron in roots exclusively ,rather than its transport to leaves .

Key woreds: Boron-toxicity, Boron-detoxification,Cucumber,Mung bean,rooting response ,Tomato and Znic .