Genotypic evaluation of cowpea germplasm for salinity tolerance at germination and during seedling growth

Abstract

Soil salinity represents a major constraint limiting crop production in arid and semi-arid countries. The effect of salinity induced by sodium chloride (NaCl) at five levels (0, 50, 100, 150 and 200 mM) was investigated on four germination traits and thirteen seedling growth characteristics in twenty cowpea [Vigna unguiculata (L.) Walp.] genotypes (ET11, KEB-CP004, KEB-CP006, KEB-CP009, KEB-CP 010, KEB-CP020, KEB-CP033, KEB-CP038, KEB-CP039, KEB-CP045, KEB-CP051, KEB-CP054, KEB-CP057, KEB-CP060, KEB-CP067, KEB-CP068, KEB-CP118, MTA22, NO74 and NO1036). The germination tests were carried out on Petri dishes in the laboratory while seedling growth experiments continued in plastic pots in the greenhouse, both setting up using a randomised complete block design with three replications. Genotypic responses were significant for all germination traits (p < 0.001). Germination percentage, germination rate index, and coefficient of velocity of germination were all decreased by salt stress. However, the mean germination time increased with increasing saline conditions. Significant differences were found between genotypes for most growth attributes. Growth rate (centimeter increased in height per week) decreased significantly with increasing salinity, starting at 100 mM NaCl (24.20% reduction, 2.66 cm / week) with maximum reduction (38.58%) corresponding to 2.16 cm/week observed at 200 mM NaCl, compared to control (3.51 cm/week growth rate). Also, significant decline in shoot weights, number of functional leaves and dry matter production were observed under salinity. Salinity also reduced water content in shoot and root and did not affect root weights. Under salinity, significant correlations were found between all germination variables (p < 0.001). Growth rate was significantly associated with ten out of the twelve other seedling growth traits. Also, the dry matter production under salinity was significantly associated with all other seedling growth characteristics with the exception of root water content. Given the effect of salt stress, cowpea genotypes, namely NO1036, KEB-CP004, KEB-CP038 and KEB-CP051, were the most tolerant while KEB-CP068 and ET11 were the most sensitive ones. The results confirm substantial genetic variation in salt stress tolerance among the studied genotypes. The most tolerant genotypes should be further explored in genetic improvement programs and should be promoted for culture in regions affected by salinity.

Comparison Adsorption of Cd (II) onto Lignin and Polysaccharide-Based Polymers

“…Further increasing the dose of adsorbent no longer had the same effect due to the phenomenon of agglom-eration of lignin particles (a fact confirmed by microscopic analyses), which can lead to the blocking of superficial functional groups and, consequently, the values of q decreased. This is in accordance with the existing observations in the specialized literature, which show that, for a given adsorbent, the retention of metal ions from aqueous solutions occurs with high productivity when the experimental conditions are well selected [35,36]. Under these conditions and based on previous experiments [26,27], but also on the preliminary tests performed (Figure 1), it was estimated that a lignin dose of 5 g/L is optimal for the elimination of Cd (II) ions from aqueous solutions.…”

“…Modeling equilibrium data obtained experimentally in order to evaluate the adsorption capacity of a given material under exact experimental conditions allows for the acquisition of particularly useful information that can then be used to design a large-scale industrial wastewater treatment system. Studies in the literature [ 36 , 37 ] highlighted the fact that the more complex the composition of a wastewater, the more adsorption systems used for its treatment must be described and selected with greater accuracy. The experimentally obtained isotherms for the adsorption of Cd (II) on lignin in the studied concentration domain are non-linear, and their slope is typical.…”

“…To evaluate the seed germination parameters, the dimensions, and the mass of the resulting seedlings, germination tests were carried out for 7 days [ 35 , 36 ] in three repetitions with batches of 10 seeds each. The seeds were disinfected with NaClO 5% for 5 min, after which they were washed three times with MilliQ ultrapure water until the characteristic smell disappeared [ 37 , 38 ].…”