Abstract
Cottonseed is widely used as a source of ruminant feed and for industrial purposes. Therefore, there is a tremendous need to improve the nutritional value of cotton embryos. In this study, a conventional management (CM) and two integrated cotton management strategies (IMS1, IMS2) were performed at two soil fertility levels to study the relationships among soil N, N assimilation, embryonic protein accumulation and protein quality. The levels of proteins, essential amino acids, and semi-essential amino acids, especially those of glutamate, lysine, and methionine, were higher in IMS1 and IMS2 embryos than in CM embryos. These changes were significantly positively correlated with the soil-available N content, glutamine synthetase activity and peak value of protein accumulation rate and were negatively correlated with the free amino acid level. These results illustrated that integrated management strategies, especially the rates and timing of N application, raise the level of soil available N, which is beneficial for N assimilation in developing cotton embryos. The protein content was limited by the rate of protein accumulation rather than by the free amino acid content. The combination of target yield fertilization, a growth-driven N application schedule, a high plant density and the seedling raising with bio-organic fertilizer can substantially improve protein quality in cotton embryos, especially at a soil with low soil organic matter and total nitrogen.
Highlights
Cotton embryos accumulate 40%–55% of their dry weight (DW) as storage protein, which has a substantial effect on their nutritional value (Alford et al, 1996; Mujahid et al, 2000)
Compared with conventional management (CM), the contents of soil available nitrogen (AV-N) in IMS1 and IMS2 increased by averages of 6.37 and 16.86%, respectively, at soil depths of 0–20 cm and by 9.72 and 21.52%, respectively, at soil depths of 20–40 cm. These results indicated that soil N availability was significantly increased in both IMS1 and IMS2 compared with CM
The initial question that motivated us to perform this study was whether matching a high-yielding variety with integrated management strategies (IMS) would prove useful in improving the nutritional value of cotton embryos
Summary
Cotton embryos accumulate 40%–55% of their dry weight (DW) as storage protein, which has a substantial effect on their nutritional value (Alford et al, 1996; Mujahid et al, 2000). Evaluating the mechanisms controlling storage protein accumulation and protein quality in these embryos is crucial step for improving seed quality. Numerous studies show the many steps involved in protein accumulation in cottonseed embryos, involving seed biochemistry (Hodges, 2002; Hernandez-Sebastia et al, 2005; Zhang et al, 2014), N transport with the plant and from the soil (De Ruiter et al, 1986; Kullmann and Geisler, 1986; Crawford and Glass, 1998), soil N levels and the environment (Macduff and Hopper, 1986). Integration of the results of these studies into a complete management system targeting the final result of protein quality in cotton embryos is still needed
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