Effects of foliar application of BAP on source and sink strength in four six-rowed barley (Hordeum vulgare L.) cultivars

Abstract

A field experiment was conducted to investigate the effects of foliar application of a synthetic cytokinin (BAP) on source and sink strength of four different six-rowed barley (Hordeum vulgare L.) cultivars. Different spraying treatments consisting of spraying on whole plant, spraying only on leaves and spraying only on ears started at anthesis and continued for 7 days. One additional spraying was carried out on late period of grain filling. Results showed that spraying only on leaves did not affect ear weight, grain yield and 1,000-grain weight, while the two other treatments increased all above mentioned traits. Neither of treatments affected stem weight, biological yield and contribution of stem reserves in grain filling. Exogenous cytokinin did not increase photosynthetic rate and chlorophyll content in treated leaves until late period of grain filling, although there was no significant increase in final grain weight due to late application of BAP. Our results suggested that effects of foliar application of BAP were mostly due to increased sink size soon after anthesis and increased sink demand probably met by current photosynthesis of organs other than leaves, like ear green tissues.

Co-ordinate regulation of cytokinin gene family members during flag leaf and reproductive development in wheat

“…In general, cytokinins may affect seed yield by enhancing sink strength and, consequently, increasing seed size, by up-regulating cell cycle related genes, through the action of sugar signalling and by enhancing phloem unloading and sugar import into the endosperm through enzymatic activity of cell wall invertase [12]. Although the beneficial effect of exogenously applied cytokinins on grain yield has been documented for several decades, including for wheat, maize, rice and barley [14-17], the application of cytokinins to field crops is limited due to the substantial cost of cytokinins. Given that changes in the levels of endogenous cytokinins will alter the regulation of many physiological processes resulting in the disruption of normal growth patterns [18], and rapid and dramatic changes in cytokinin concentration have been observed during panicle and early grain development in a number of crop species including wheat [19-21] and rice [8,22], yield improvement through genetic manipulation of cytokinin synthesis and metabolism genes to artificially manipulate the endogenous cytokinin levels could be of considerable importance.…”

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“…Indeed, endogenous cytokinin levels are critically involved in the regulation of early fruit growth through the regulation of cell division by D-type cyclin expression (Baldet et al, 2006). Similar results were also observed with barley (Hordeum vulgare L.), wherein the effects of foliar application of 6-BA resulted in increased sink size soon after anthesis and increased sink demand was met by current photosynthesis of organs (Hosseini et al, 2008). However, the application of CPPU had some adverse effects on grapes, including inhibiting anthocyanin and sugar accumulation (Khalil-Ur-Rehman et al, 2017).…”

Response of Bread Wheat Cultivars to Terminal Water Stress and Cytokinin Application from a Grain Phenotyping Perspective

“…The lack of a significant effect observed from the application of 6-BA reinforces the belief that the interplay between environmental factors and genotypes plays a crucial role in the response to treatments. Numerous studies have utilized varying concentrations of 6-BA to enhance yield-related traits and improve the tolerance of different plant species to abiotic stresses [44][45][46]. Although the concentration employed in this study was inspired by the study of Yang et al (2016), who concluded that this specific concentration led to an increase in wheat grain yield by improving stay-green characteristics under heat stress conditions [11], furthermore, it is worth considering that the cultivars utilized in our study may not have exhibited a significant response in terms of TGW when subjected to 6-BA treatment.…”