The effect of cadmium and lead pollution on growth and physiological parameters of field beans (Vicia faba)

V. Alle¹*, A. Osvalde², M. Vikmane¹ and U. Kondratovics¹

¹University of Latvia, Faculty of Biology, Department of Plant Physiology, 1 Jelgavas street, LV-1004 Riga, Latvia
²University of Latvia, Institute of Biology, Laboratory of Plant Mineral Nutrition, 3 Miera street, LV-2169 Salaspils, Latvia
*Correspondence: vita.alle@lu.lv

Abstract:

Research on the impact of soil contamination on crops is important as plants directly take up heavy metals from the soil through the roots, so heavy metals can enter the food chain. The aim of this study was to investigate the impact of cadmium (Cd) and lead (Pb) pollution on growth and physiological parameters of field beans. Plants in the vegetation experiment were grown under controlled conditions. Changes in growth and physiological parameters were studied at five levels of Cd (0–25 mg L^-1) and at 6 levels of Pb in substrate: from (0–1,000 mg L^-1) at the first day of the experiment, to (0–2,000 mg L^-1) at the end of the experiment after gradual Pb additions after every sample collecting day. Methods used for analysing the plant material: the content of amino acid proline and photosynthetic pigments were determined by spectrophotometry; chlorophyll a fluorescence parameters – using continuous excitation chlorophyll fluorimeter. The fresh weight of plant above-ground parts and roots was detected. The growth and development of field beans was slightly influenced by increasing amount of Cd and Pb in substrate only at the end of the experiment. The highest Cd treatments (Cd20 and Cd25) caused 2.5 and 1.3 times increased proline concentration in bean leaves. The chlorophyll a + b content and chlorophyll a fluorescence parameter F_v/F_m changed differently throughout the experiment. In general, during the experiment, there was a tendency for the content of proline in leaves for Pb treatments to be increased compared to control. At the end of the experiment the content of proline in field bean leaves of the highest Pb treatments (Pb600 + 100 + 400 + 500, Pb800 + 100 + 400 + 500 and Pb 1,000 + 100 + 400 + 500) was 1.66, 1.44 and 1.55 times higher, respectively, than that of the control plant leaves. The negative impact of exposure to Pb on chlorophyll a + b, chlorophyll a fluorescence parameter P_Index and F_v/F_m in bean leaves was less pronounced compared to Cd. The obtained results confirm that field beans until their flowering stage can grow and develop in the presence of a large amount of Cd and Pb in substrate without significant growth inhibition and detrimental impact on physiological parameters, if optimal cultivation conditions are provided.

Key words:

heavy metals, photosynthesis parameters, proline, Vicia faba

Germination and growth of primary roots of inoculated bean (Vicia faba) seeds under different temperatures

A. Senberga*, L. Dubova and I. Alsina

Latvia University of Agriculture, Institute of Soil and Plant Sciences, Liela street 1, LV-3001 Jelgava, Latvia
*Correspondence: alise.senberga@llu.lv

Abstract:

Temperature stress strongly affects legumes, rhizobia, and the efficiency of legume-rhizobia interaction. An experiment in 2016 was developed to test the seed germination in Petri dishes using different microorganism inoculation under several temperature treatments (4, 8, 12 and 20 °C). The goal of this study was to test the effect of rhizobium inoculation under low root zone temperature, and to examine whether the addition of mycorrhiza fungi could enhance rhizobia resistance to abiotic stress and improve faba bean (Vicia faba) germination. Four faba bean cultivars were selected for the experiment (‘Lielplatone’, ‘Fuego’, ‘Bartek’ and ‘Karmazyn’). Four different seed inoculation variants were included in this experiment – 1) with rhizobium inoculation; 2) with a commercial preparation containing mycorrhiza fungi; 3) inoculation with both rhizobium and the mycorrhiza fungi preparation; 4) control variant. The number of germinated seeds, the length of the primary root and the primary root weight ratio were determined. The effect of inoculation was found out to be dependent not only on the temperature treatment, but it also significantly varied between the bean cultivars. Variants where seeds were inoculated with both mycorrhiza and rhizobia resulted in the highest results (length and weight ratio of primary roots), comparing with other inoculation variants, regardless of temperature. Variants where seeds were treated only with rhizobia mostly showed the lowest results – both length and weight ratio of primary roots, especially under treatment of 4 °C. Faba bean inoculation with only rhizobia might not be efficient, when sowing seeds under a low temperature stress. Inoculation with both rhizobia and mycorrhiza fungi could be a potential solution, when the root zone temperature is still below the optimal temperature.

Key words: