Seed enhancement with cytokinins: changes in growth and grain yield in salt stressed wheat plants

Abstract

Cytokinins are often considered abscisic acid (ABA) antagonists and auxins antagonists/synergists in various processes in plants. Seed enhancement (seed priming) with cytokinins is reported to increase plant salt tolerance. It was hypothesized that cytokinins could increase salt tolerance in wheat plants by interacting with other plant hormones, especially auxins and ABA. The present studies were therefore conducted to assess the effects of presowing seed treatment with varying concentrations (100, 150 and 200 mg l -1 ) of cytokinins (kinetin and benzylaminopurine (BAP)) on germination, growth, and concentrations of free endogenous auxins and ABA in two hexaploid spring wheat (Triticum aestivum L.) cultivars. The primed and non-primed seeds of MH-97 (saltintolerant) and Inqlab-91 (salt-tolerant) were sown in both Petri dishes in a growth room and in the field after treatment with 15 dS m -1 NaCl salinity. Both experiments were repeated during 2002 and 2003. Among priming agents, kinetin was effective in increasing germination rate in the salt-intolerant and early seedling growth in the salt-tolerant cultivar when compared with hydropriming under salt stress. Thus, during germination and early seedling growth, the cytokinin-priming induced effects were cultivar specific. In contrast, kinetin-priming showed a consistent promoting effect in the field and improved growth and grain yield in both cultivars under salt stress. The BAP-priming did not alleviate the inhibitory effects of salinity stress on the germination and early seedling growth in both cultivars. The increase in growth and grain yield in both cultivars was positively correlated with leaf indoleacetic acid concentration and negatively with ABA concentration under both saline and non-saline conditions. The decrease in ABA concentration in the plants raised from kinetinprimed seeds might reflect diminishing influence of salt stress. However, the possibility of involvement of other hormonal interactions is discussed.

Salt tolerance and regulation of gas exchange and hormonal homeostasis by auxin-priming in wheat

“…Recently matured top leaves were used for the determination of different phytohormones at boot stage. Auxins (IAA, IBA) and ABA were extracted and purified as described by Kusaba et al (1998), with some modifications (Iqbal et al, 2006). The quantification of plant hormones was done by high performance liquid chromatograph (HPLC) using authentic standards run through for the whole procedure, as previously described (Iqbal et al, 2006).…”

Pericarp Loosening and Reduced Lipid Peroxidation Enhances Spinach Seed Performance and Biomass Production Under Normal and Saline Conditions

“…Katzman et al (2001) also reported that soaking/washing in NaCl/water remove inhibitors from the pericarp and also enhance seed germination and vigor to perform well under high temperature and normal conditions. Use of growth regulators has ameliorated the drastic effect of salinity in several crops (Egamberdieva, 2009;Iqbal et al, 2006;Iqbal and Ashraf, 2010). Therefore, we tried several seed treatments to enhance germination and vigor of spinach seeds.…”

“…Significant improvement in germination of spinach due to seed treatment with bleach and hydrogen peroxide was also recorded by Katzman et al (2001), which further support our results. Germination enhancement in response to priming using distilled water (Amjad et al 2007), IAA (Afzal et al, 2005) and cytokinins (Iqbal et al, 2006) has been reported in various crops. Priming with IAA might have increased the endogenous level of GA (Wolbang et al, 2004), that is supposed to reduce the endogenous ABA (Gonai et al, 2004), and thus promoted seed germination, emergence and vigor of spinach seeds.…”

“…Priming with IAA might have increased the endogenous level of GA (Wolbang et al, 2004), that is supposed to reduce the endogenous ABA (Gonai et al, 2004), and thus promoted seed germination, emergence and vigor of spinach seeds. It is a wellestablished fact now that salinity reduces the endogenous level of IAA (Iqbal et al, 2006;Prakash and Prathapasenan, 1990;Wang et al, 2001). IAA priming might have replenished the endogenous IAA concentration and thus enhanced germination, emergence and seedling vigor as compared to control (untreated) and other seed treatments.…”

“…In addition, exogenous IAA showed high stimulatory effect on the root and shoot growth of wheat seedling in saline condition (Egamberdieva, 2009). Other plant growth regulators, such as GA3 (Iqbal and Ashraf, 2010) and cytokinins (Iqbal et al, 2006;Zahir et al, 2001) have also been reported to improve germination and plant growth under saline stress. At present, the information regarding the role of priming with auxins or cytokinins, and their effect on salt stress tolerance in spinach are scarce.…”