Carbon-11 Radiotracing Reveals Physiological and Metabolic Responses of Maize Grown under Different Regimes of Boron Treatment

Abstract

In agriculture, boron is known to play a critical role in healthy plant growth. To dissect the role of boron in maize metabolism, radioactive carbon-11 (t½ 20.4 min) was used to examine the physiological and metabolic responses of 3-week-old B73 maize plants to different levels of boron spanning 0 mM, 0.05 mM, and 0.5 mM boric acid (BA) treatments. Growth behavior, of both shoots and roots, was recorded and correlated to plant physiological responses. 11CO2 fixation, leaf export of [11C]-photosynthates, and their rate of transport increased systematically with increasing BA concentrations, while the fraction of [11C]-photosynthates delivered to the roots under 0 mM and 0.5 mM BA treatments was lower than under 0.05 mM BA treatment, likely due to changes in root growth. Additionally, solid-phase extraction coupled with gamma counting, radio-fluorescence thin layer chromatography, and radio-fluorescence high-performance liquid chromatography techniques applied to tissue extracts provided insight into the effects of BA treatment on ‘new’ carbon (as 11C) metabolism. Most notable was the strong influence reducing boron levels had on raising 11C partitioning into glutamine, aspartic acid, and asparagine. Altogether, the growth of maize under different regimes of boron affected 11CO2 fixation, its metabolism and allocation belowground, and altered root growth. Finally, inductively coupled plasma mass spectrometry provided insight into the effects of BA treatment on plant uptake of other essential nutrients. Here, levels of boron and zinc systematically increased in foliar tissues with increasing BA concentration. However, levels of magnesium, potassium, calcium, manganese, and iron remained unaffected by treatment. The rise in foliar zinc levels with increased BA concentration may contribute to improved 11CO2 fixation under these conditions.

Treatments with Liquid Smoke and Certain Chemical Constituents Prevalent in Smoke Reduce Phloem Vascular Sectoriality in the Sunflower with Improvement to Growth

“…11 CO 2 (t ½ 20.4 min) was produced on the GE PETtrace Cyclotron located at the Missouri Research Reactor Center using high-pressure research grade N 2 gas target irradiated with a 16.4 MeV proton beam to generate 11 C via the 14 N(p,α) 11 C nuclear transformation [ 48 , 49 ] using our published procedures [ 50 , 51 , 52 ]. 11 CO 2 was administered via a leaf cell that was affixed to a targeted source leaf ( Figure 1 ).…”

Azospirillum brasilense Bacteria Promotes Mn2+ Uptake in Maize with Benefits to Leaf Photosynthesis

“…Leaf chlorophyll concentrations were measured using our prior published procedures [ 37 ]. In short, leaf 2 samples were ground in liquid nitrogen and extracted in acetone.…”

Boron Impact on Maize Growth and Yield: A Review

“…B deficiency in maize can significantly impact root growth. The research indicates that under B deficiency, maize plants exhibit shorter roots and a reduction in lateral root number [25]. This deficiency can lead to root growth cessation, as well as the disappearance of the root cap, ultimately inhibiting root growth.…”

“…Therefore, ensuring adequate B levels is crucial for the healthy root development of maize plants [23,27]. Furthermore, Wilder et al [25] demonstrate the impact of B deficiency on yield through abnormal development of reproductive structures, resulting in smaller cobs with fewer kernels. The study pinpoints the link between B deficiency and male sterility, highlighting its importance for viable pollen and proper seed development.…”

“…Boron plays a crucial role in the physiology and function of maize. B deficiency can lead to shorter roots, reduced lateral root number, and a significant impact on metabolic and physiological processes, ultimately affecting the growth, development, and yield of maize [25] (Fig. 2-a, b, & c).…”