Effects of exogenous ABA and cytokinin on leaf photosynthesis and grain protein accumulation in wheat ears cultured in vitro

Abstract

A detached culture system and steady-state 15 N labeling technique were used to study the effects of exogenous ABA and ZR on photosynthetic characteristics, nitrogen remobilization and the activities of key enzymes for nitrogen metabolism in detached wheat parts during grain protein accumulation. The differences in net photosynthetic rate, chlorophyll content (SPAD value) and soluble protein content in the flag leaves of detached culture system between the treatments of ABA and ZR showed that ABA facilitates the post-anthesis senescence course compared to the ZR treatment. The differences in the changes of 15 N amount in different organs in the detached culture system between the ABA and ZR treatments showed that nitrogen remobilization from vegetative organs to the grain is accelerated by the ABA treatment but is delayed by ZR. The activities of GS and GPT in grains treated with ABA were significantly higher than those with the control treatment at 5 DAC, but reduced significantly compared with control at 11 DAC. The two enzyme activities in grains were reduced significantly by ZR at 5 DAC and increased significantly at 11 DAC, compared with those treated with ABA. The above changes of enzyme activity showed that the ABA treatment hastens amino acid conversion into grains and protein accumulation in grains, whereas the ZR treatment delays these processes. A significant reduction in grain weight with ABA treatment is associated with the reduction of net photosynthesis, chlorophyll content, and soluble protein content in flag leaves. Compared with the control and ZR treatments, a significant increase in grain protein content with the ABA treatment may result from the accelerating effects of ABA on N remobilization, amino acid conversion into grains and protein accumulation in grains.Abbreviations: ABA -abscisic acid; DAC -days after culture; GPT -glutamate pyruvate transaminase; GS -glutamine synthetase; ZR -zeatin riboside; RuBPCO -ribulose bisphosphate carboxylase oxygenase

Cytokinin promotes catalase and ascorbate peroxidase activities and preserves the chloroplast integrity during dark-senescence

“…The current paper confirmed that BAP delays senescence in wheat (Xie et al, 2004) in the dark, as has been demonstrated also in broccoli florets (Costa et al, 2005), maize (He et al, 2005) rice (Ookawa et al, 2004). Sixty percent of initial levels of chlorophylls were retained, as was 77% of total leaf protein.…”

Effects of ABA on primary terpenoids and Δ9-tetrahydrocannabinol in Cannabis sativa L. at flowering stage

“…A decrease in chlorophyll content has also detected in barley, wheat, and soybeans plants treated with ABA (Samet et al 1980;Cuello et al 1995;Xie et al 2004). In the present study ABA treatment caused a decrease in the carotenoid content in female plants.…”

Effects of the exogenous application of auxin and cytokinin on carbohydrate accumulation in grains of rice under salt stress

“…In addition, the growth and yield parameters of rice were shown to be significantly increased in response to the application of cytokinin (kinetin) and its physiological precursors (Zahir et al 2001). Xie et al (2004) have reported the effects of exogenous hormones on the translocation of carbohydrates (e.g., sucrose) to developing grains, the accumulation of starch and the activity of related metabolic enzymes in grain. For example, exogenous cytokinin (Asthir et al 1998) and IAA (Darussalam and Patrick 1998) can promote sucrose accumulation in the developing grains of wheat.…”