Seed vigor of maize (Zea mays) cultivars affected by position on ear and water stress

A field experiment was conducted in 2014 to investigate the effects of different irrigation treatments (I1, I2, I3 and I4: irrigation after 60, 80, 100 and 120 mm evaporation from class A pan, respectively), cultivars (SC704, NS640 and DC303: late, mid and early maturing, respectively) and positions on ear (upper, lower and middle) on seed vigor of maize. The experiment was arranged as split-split plot based on RCB design with three replications. Irrigation treatments, cultivars and seed positions were considered as main, sub and sub-sub plots, respectively. Although, water limitation had no significant effect on seed weight, seeds produced under limited irrigation conditions showed low vigor as measured by electrical conductivity of seed leachates, germination rate and seedling dry weight. Seeds of SC704 germinated earlier and consequently produced larger seedlings in comparison with other cultivars. The higher seedling dry weight of the lower position seeds of ear was mainly the result of larger reserve accumulation and rapid germination. The advantage of the lower position seeds was more evident under severe water deficit. Thus, selection of the large and uniform seeds could be a simple way for improving seed and seedling vigor in maize cultivars

Early response of Solanum nigrum L. to Lumax and castor oil combination in relation to antioxidant activity, osmolyte concentration and chlorophyll a fluorescence

Abstract Solanum nigrum L. (Black nightshade), is one of the most troublesome weeds of summer crops such as corn, soybean, sunflower, etc. To study the effect of combined Castor oil as an adjuvant with different doses of Lumax (Mesotrion + S-metolacholor + Terbuthylazine) on the physiological behavior of Solanum nigrum L., a greenhouse experiment was conducted in randomized complete block design with four replications in agricultural faculty of the University of Tabriz in 2021. A foliar application of Lumax increased proline, malondialdehyde, and hydrogen peroxide concentrations and superoxide dismutase, catalase, and peroxidase activity. The content of protein and photosynthetic pigments (Chlorophyll a, b, and carotenoids) also decreased significantly by using Lumax herbicide. Applying castor oil in combination with Lumax intensifies oxidative stress and lipid peroxidation. Results showed that by increasing the herbicide doses in comparison with control (non-herbicide), Area, Fm, Fv, Fv/Fm, Fv/F0, Sm, Sm/Tfm, and Fv/F0 decreased 48.32%, 19.52%, 27.95%, 10.47%, 50.90%, 28.34%, 79.38%, and 50.90%, respectively and F0, F0/Fm increased 46.76% and 82.38%, respectively. Castor oil showed a synergistic effect on Lumax herbicide and enhanced its efficacy on Solanum nigrum. The presented results supported the view that by evaluating chlorophyll a fluorescence parameters, we would realize herbicide (alone or mixed with any adjacent) efficacy before the visual symptoms appear in the plant

Early Identification of Herbicide Modes of Action by the Use of Chlorophyll Fluorescence Measurements

The effect of seven herbicides (U-46 Combi Fluid, Cruz, MR, Basagran Bromicide, Lumax, and Gramoxone) on Xanthium strumarium plants was studied. Chlorophyll content and fluorescence, leaf temperature, and stomatal conductance were evaluated at 12 h, 36 h, 60 h, and 84 h after herbicides application. U46 Combi Fluid, Cruz, and MR did not have a significant effect on chlorophyll fluorescence induction curves as compared to the control treatment. However, Basagran, Bromicide, Lumax, and Gramoxone showed significant changes in the shape of polyphasic fluorescence transients (OJIP transients). Variations in chlorophyll content index, leaf temperature, and stomatal conductance parameters were dependent on the type of applied herbicide. Our study revealed that the specific impact of the applied herbicides on the photosynthetic efficiency of plants is related to their chemical groups and their mechanism of action