Manganese Deficiency and Toxicity Effects on Photosynthesis, Chlorophyll, and Transpiration in Wheat¹

Abstract

Wheat (Triticum aestivum L.) production areas are expanding to soils low in available Mn in southern Georgia and to soils high in available Mn in northern Georgia. Useful data on Mn deficient and toxic levels in leaf tissue for top growth and physiological processes in wheat are needed to evaluate growth processes limiting wheat production. The objectives of this study were to correlate Mn deficiency and toxicity levels with top dry weight production, photosynthesis, chlorophyll concentration, and transpiration. Wheat plants were grown in 10 experimental concentrations ranging from 0.09 μM to 9.1 mM in nutrient solution. Photosynthesis and transpriration measurements were made on blade 1 of plants grown in the greanhouse. Total chlorophyll and Mn concentrations were determined on the experimental tissue after freeze‐drying. Foliar dry weights on a per pot (15 plants) basis were also determined. Severe Mn deficiency depressed top dry weight, photosynthesis, and total chlorophyll concentration, but transpiration was unaffected. Mild Mn toxicity reduced top dry weight but not photosynthesis, total chlorophyll concentration, or transpiration. Critical Mn deficiency levels for reducing top dry weight and apparent photosynthesis rates were similar, namely 0.23 and 0.30 mmol kg−1, repectively. Growth reduction from Mn deficiency is possibly due to reduced photosynthesis. Minimum Mn requirements for chlorophyll (0.14 mmol kg−1) is about one‐half of that for top production. The critical Mn deficiency level for transpiration could not be determined. The critical Mn toxicity level for top dry weight occurred at 7 mmol kg−1. Concentrations of 19, 19, and 24 mmol kg−1 were required for the depression of photosynthesis, total chlorophyll concentration, and transpiration, respectively. Maximum growth and yield are expected when the range of Mn concentration in blade 1 is 0.23 to 7 mmol kg−1. The critical levels are prelimilinary values to be used in evaluating Mn status of field‐grown wheat for possible deficiency and toxicity.

Influence of Manganese Deficiency and Toxicity on Isoprenoid Syntheses

“…The total top dry weight per pot consisted of 3 plants. A second Manganese is a required microelement for growth and photosynthesis of heterotrophic and autotrophic plants (2,3,8,9,(17)(18)(19)(20). Excess concentrations of Mn in plant tissues result in decreased growth (9,10,(17)(18)(19)(20).…”

“…Carbon dioxide reductiW was conducted by previously published methods (20). Four GA Extraction and Quantitation.…”

“…(6,30 (9,(17)(18)(19)(20). The exact form of the response curve depends upon species and varieties (9,12,19,20 (Table II). Mn is known to be required for PSII at concentrations about 1 mol Mn/l00 mol Chl (22,26,32).…”

How Soil Nutrient Availability Influences Plant Biomass and How Biomass Stimulation Alleviates Heavy Metal Toxicity in Soils: The Cases of Nutrient Use Efficient Genotypes and Phytoremediators, Respectively

“…Such possible factors could be a better compartmentalization of Mn within cells and/or functionality of Mn detoxification systems [13]. Significant growth reductions of several plant species, grown under Mn toxicity conditions, have been mentioned by several researchers [61][62][63][64][65].…”

Early Inhibition of Photosynthesis during Development of Mn Toxicity in Tobacco

“…These studies are focused primanly on toxicity effects on photosynthesis. a process which becomes inhibited following long-term excess accumulationi of leaf Mn (27). In all experiments, at least one plant was harvested from each container at the time Mn treatments were imposed (designated d 0) and on each day up to 9.…”