Plant genotype differences to ferrous and total iron in emerging leaves. II. Dry beans and soybeans

Abstract

Ferrous iron (Iron²⁺ and Fe²⁺) and total Fe were determined in “Fe‐tolerant”; and “Fe‐susceptible”; dry bean (Phaseolus vulgaris L.; UI 59 and PI 165078) and soybean (Glycine max L.; A2, T203, and Hawkeye) genotypes to evaluate their differential responses to Fe deficiency stress. Plants were grown in growth chambers in solutions with Fe (+Fe) and without Fe (‐Fe). Once Fe deficiencies appeared in plants grown in ‐Fe solutions, samples of the emerging trifoliate leaves were collected daily for analysis. After plants showed relatively severe Fe deficiency chlorosis symptoms when grown in ‐Fe solutions, supplemental Fe was added to plants grown in each treatment solution.

Iron²⁺ in the newly emerging trifoliate leaves, whether chlorotic or green and regardless of time plants were in treatment, remained relatively constant. However, total Fe changed almost daily dependent on Fe deficiency stress and genotype. When grown in ‐Fe solutions, total Fe in both dry bean and soybean genotypes decreased until plants responded to the Fe deficiency stress and enhanced total Fe values even without the addition of Fe to solutions. Plants also overcame the chlorosis symptoms. The more “Fe‐tolerant”; genotypes responded more rapidly to Fe deficiency stresses by increasing total Fe and did not decrease total Fe as low as the “Fe‐susceptible”; genotypes. Total Fe values changed somewhat rhythmically in the leaves. Dry beans and soybeans showed greater ability to overcome Fe deficiency stresses compared to sorghum [Sorghum bicolor (L.) Moench] and maize (Zea mays L.), the subject of a companion article. Total Fe was related to severity of Fe deficiency chlorosis symptoms, but Fe²⁺ was not. The daily fluctuations of total Fe could help explain why chlorotic leaves often contain more Fe than green leaves and some of the wide variability often noted in plant tissue analyses for Fe.

Key words:

• Mineral nutrition
• Fe nutrition
• plant genotype differences to Fe
• Fe utilization by plants
• Fe efficiency
• Fe tolerance
• Phaseolus vulgaris
• Glycine max