Von D. Jolley

Plant Metabolie Responses to Iron-deficiency StressA variety of mechanisms, grouped into two major strategies, make iron available from the soil

germinating soybean seed contains sufficient iron to supply the plant until the first trifoliate leaf is produced. If a continuous supply of iron from the growth medium is not then available, the plant develops iron chlorosis-a yellowing that can be alleviated by supplying the plant with suitable iron compounds. This disorder is particularly prevalent on calcareous soils, found on approximately one-third of the earths surface. In these soils, it is difficult to maintain iron in forms that

Comparative evaluation of factors involved in Fe stress response in tomato and soybean

Abstract Iron‐efficient and Fe‐inefficient tomato (Lycopersicon esculentum Mill; T3238FER and T3238fer, respectively) and soybean (Glycine max (L.) Merr.; A7 and T203, respectively) were grown in modified Hoagland solutions with varying levels of Fe (0, 0.025, 0.05, and 0.75 mg Fe L‐1). The release of H+ ions, reductants and reduction of Fe3+ to Fe2+ by the root, and concentration of nutrients in plant leaves and roots were measured to determine if these factors interact during the Festress response mechanism. The FER tomato responded to Fe stress by increasing H ion and reductant release concurrently with increased reduction of Fe3+ by the roots; all three reached maximum levels at the same time (day 7). Iron‐stressed A7 soybean responded first with increased H+ ion release and reduction by the roots, while reductant release lagged about 1 day behind. In both cases, increased concentration of leaf Fe corresponded to the time of maximum Fe‐stress response. The Fe‐inefficient T3238fer tomato and T203 soybe...

Root iron‐reduction capacity for genotypic evaluation of iron efficiency in soybean

Abstract Genetic resistance to Fe‐deficiency chlorosis is the most viable and economical means to overcome this problem in soybean [Glycine max (L.) Merr.], but current field evaluation is slowed and constrained by soil heterogeneity and environmental fluctuation. Highly resistant (Fe‐efficient) cultivars have been shown to reduce Fe3+ to Fe2+ more actively by the roots under Fe‐deficiency stress than highly susceptible genotypes. The objective of this study was to determine if Fe3+ reduction could be used to predict the degree of resistance or susceptibility to Fe‐deficiency chlorosis. Thirteen genotypes (both commercial and experimental) with known field susceptibility ratings were grown in a growth chamber in modified Hoagland solution. The more Fe‐efficient genotypes reduced Fe3+ earlier and to a greater extent than the less Fe‐efficient types. The sum of the seven daily Fe3+ reduction measurements was negatively correlated with field chlorosis ratings, as high as ‐0.864 (p > 0.01), and was a good pre...

Screening for resistance to iron deficiency chlorosis in dry bean using iron reduction capacity

Abstract Identifying cultivars resistant to iron (Fe) deficiency chlorosis so prevalent in calcareous soils is a more economical solution than fertilizer application in field crops. The current method of screening for resistance using chlorosis ratings in field trials is time consuming and highly variable. Root Fe reduction successfully separated cultivars or rootstocks, varying widely in resistance, of soybean (Glycine max L.), peach (Prunus persica L.), and grape (Vitis spp.), but was unsuccessful in sub‐clover (Trifolium subterraneum L.). Dry bean (Phaseolus vulgaris L.) exhibits Fe deficiency chlorosis in calcareous soils and initiates Fe reduction by the roots in response to such stress. The resistance of 24 dry bean cultivars to Fe deficiency chlorosis was assessed by measuring and summing daily Fe reduction by the roots. The cultivars were grown both hydroponically in an environmental chamber in low Fe solutions (0.05 mg‐L‐1) and at three field sites in both 1995 and 1996. A significant relationshi...

Nutritional and Management Related Interactions with Iron-Deficiency Stress Response Mechanisms

Abstract Iron (Fe) deficiency symptoms develop in many agricultural and horticultural settings and generally occur when susceptible genotypes are grown in calcareous soils where Fe availability is limited. However, in some situations, Fe deficiency develops as a result of biological interactions with factors other than limited available Fe. We review physiological explanations for some factors known to interact with iron-deficiency stress. The discussion includes interactions with macronutrients and micronutrients, management factors such as grazing and companion cropping, and symbiotic nitrogen fixation. We also refer to several field observed interactions with Fe deficiency in soybean [Glycine max (L.) Merr.], where physiological explanations are yet to be identified. These include interactions with seeding rate and application of the herbicide glyphosate on glyphosate tolerant varieties. We believe that elucidation of additional physiological answers for field observations are critical to efficient and economic viability of world food production.

Iron efficient and inefficient oats. I: Differences in phytosiderophore release

Abstract It has been known for some time that graminaceous species do not respond to Fe stress in the same way as dicots. Until the recent discovery of phytosiderophores in grass species, it has not been possible to characterize known differences in the ability of various cultivars of grasses to obtain Fe. The object of this study was to determine if differences in Fe‐inefficient TAM 0–312 and Fe‐efficient Coker 227 oats are due to their abilities to release a phytosiderophore when under Fe‐deficiency stress. The two cultivars were grown in modified Hoagland solution at several levels of Fe and the release of Fe3+ solubilizing compounds (phytosiderophore), chlorosis development, and the concentration of Fe were routinely assessed as indicators of Fe stress. There was a marked difference between TAM 0–312 and Coker 227 oats in the release of phytosiderophore from their roots. The amount of phytosiderophore released from Coker 227 roots increased as the nutrient Fe concentration increased from 0 to 1.2 mg/L...

Mycorrhizal colonization and nutrient uptake of dry bean in manure and compost manure treated subsoil and untreated topsoil and subsoil

Abstract Eroded or leveled Portneuf silt loam soils (coarse‐silty mixed mesic Durixerollic Calciorthid) have been restored to topsoil productivity levels by manure application, but not by other organic sources such as cheese whey. In dry bean (Phaseolus vulgaris L. cv. Viva), only soil organic matter and Zn concentration of leaf tissue correlated with improved yields. Manure application could potentially increase or decrease mycorrhizal colonization depending on which factors dominate. Manured and unmanured soils from a long‐term field experiment were sampled and mycorrhizal spores were quantified, but there was no significant manure treatment effect on spore numbers. A greenhouse study was conducted to see if manure or composted manure freshly applied to subsoils would facilitate mycorrhizal colonization in dry bean roots compared to untreated topsoil or conventionally fertilized subsoil. Low level colonization (< 5%) was observed 21 days after planting and that increased to 58% by 56 days after planting...

Factors in iron‐stress response mechanism enhanced by Zn‐deficiency stress in Sanilac, but not Saginaw navy bean

Abstract Zinc‐inefficient Sanilac and Zn‐efficient Saginaw navy bean (Phaseolus vulgaris L.) differ in their susceptibility to Zn‐deficiency stress. Sanilac accumulates Fe under Zn‐deficiency stress and Saginaw does not. These two navy bean cultivars were grown at 0, 0.006 and 0.12 mg/L Zn in modified Hoagland nutrient solution. Various Fe‐stress response mechanisms were quantified periodically over a 12‐day experimental period to determine if known factors in the Fe‐stress response mechanism were enhanced by Zn‐deficiency stress. Visual Zn‐deficiency symptoms were more severe in Sanilac than Saginaw navy bean under equivalent Zn treatments. Sanilac contained lower leaf Zn than Saginaw when Zn was present in solution (0.006 and 0.12 mg/L Zn), but the two cultivars were similar in leaf Zn in the absence of Zn (0 mg/L Zn). Sanilac accumulated more leaf Fe than Saginaw when under Zn stress (0 and 0.006 mg/L Zn). The higher levels of leaf Fe in Sanilac than Saginaw were closely associated with enhanced releas...

Plant utilization of iron solubilized by oat phytosiderophore

Abstract Responses to Fe‐deficiency stress have been classified as Strategies I and II. “Iron‐efficient”; cultivare within each strategy exhibit one or more of a combination of specific physiological responses to Fe‐deficiency stress, while “Fe‐inefficient”; cultivars do not. Iron‐efficient Coker 227 oat (Avena byzantina C. Koch.) is a Strategy II plant which produces an Fe‐chelating compound (phytosiderophore) in response to Fe‐deficiency stress. The objective of this paper is to summarize the results of studies in which the abilities of several plant species to utilize Fe solubilized by oat phytosiderophore were determined. Experiments were conducted in which Fe‐deficiency stressed oat plants were grown in hydroponic solutions (1.2 mg Fe L‐1 unchelated) in combination with three different species of both monocotyledonous and dicotyledonous plants which represented a wide range of Fe‐efficiency. The cultivars varied in response to the oat phytosiderophore as follows: (a) WF9 maize (Zea mays L.), TAM 0–31...

PHOSPHORUS AND MANGANESE INTERACTIONS AND THEIR RELATIONSHIPS WITH ZINC IN CHELATOR-BUFFERED SOLUTION GROWN RUSSET BURBANK POTATO

Manganese (Mn)- and zinc (Zn)-driven antagonistic interactions with high available phosphorus (P) can result in negative impacts on potato cropping systems. Two chelator-buffered hydroponic experiments were conducted with Russet Burbank potato to elucidate P and Mn relationships and associated interactions with Zn. In both experiments, a P concentration decline in new shoots, old shoots, and roots resulted as solution Mn changed from deficient to sufficient followed by a P concentration rise as solution Mn changed to excessive concentrations. New and old shoot Zn concentrations generally increased with augmented solution Mn in the variable Mn experiment, but no significant changes were found in root Zn contents. Available Mn was observed to control plant P concentrations and to influence Zn uptake and translocation; thus, Mn has considerable impact on uptake and distribution of P and Zn and on P-Zn interactions in potato.