Differential responses of Hollyhock (Alcea rosea L.) varieties to salt stress in relation to physiological and biochemical parameters.

The response of 14 Hollyhock (Alcea rosea L.) varieties to salinity were evaluated in a field experiment over two growing seasons. Carotenoid, Chl a, Chl b, total Chl, proline and MDA content, CAT, APX and GPX activity and petal and seeds yields were determined in order to investigate the mechanism of salt tolerance exhibited by Hollyhock, and too identify salt tolerant varieties. Overall, the photosynthetic pigment content,petal and seed yields were reduced by salt stress. Whereas the proline and MDA content, and the CAT, APX and GPX activities increased as salt levels increased. However, the values of the measured traits were dependent upon the on the level of salt stress, the Varietie and the interaction between the two variables. Based upon the smallest reduction in petal yield, the Masouleh variety was shown to be the most salt tolerant, when grown under severe salt stress. However, based upon the smallest reduction in seed yield, Khorrmabad was the most tolerant variety to severe salt stress. These data suggest that the selection of more salt tolerant Hollyhock genotypes may be possible based upon the wide variation in tolerance to salinity exhibited by the varieties tested.

Allelopathic Effect of Aqueous Extracts of Grass Genotypes on Eruca Sativa L.

The aim of the current research is to evaluate the allelopathic activity of fifty grass genotypes from different species and to identify phenolic compounds in the genotypes that have the highest allelopathic activity and inhibitory effect on Eruca sativa L. (Rocket). Aqueous extract was prepared from the leaves of grass genotypes in different concentrations and its effect on germination and growth of E. sativa L. was measured. According to the results, the type of genotype and the concentration of the extract significantly decreased the percentage of germination, hypocotyl length, radicle length, and dry weight of E. sativa L. seedlings. Increasing the concentration of the extract resulted in a decrease in germination and growth of seedlings. The genotypes of Festulolium (Festulolium) (GR 5009, GR 1692, GR 5004) had the most inhibitory effect on the growth of E. sativa L. Also, among the genotypes studied, two genotypes (DG-M) and (DG-P) of Dactylis glomerata L. (orchardgrass) species showed the least allelopathic activity. The results of HPLC-MS indicated nine phenolic compounds including caffeic acid, syringic acid, vanillic acid, p-coumaric acid, ferulic acid, apigenin acid, chlorogenic acid, 4-hydroxybenzoic acid, and gallic acid. The phenolic compound most present in the aqueous extract was caffeic acid. However, phenolic compounds derived from Festulolium genotypes showed the greatest allelopathic action on the growth parameters of E. sativa L. The aqueous extracts of the Festulolium genotypes can be considered valid systems of sustainable weed control thanks to the phytocomplex rich in phenols.

Changes in activities of antioxidant enzymes in radish (Raphanus sativus) seedlings in response to allelopathic effect of safflower (Carthamus tinctorius)

Abstract ROS (Reactive Oxygen Species) production is a usual plant reaction to environmental stresses such as allelopathy. Plants possess antioxidant enzymes to scavenge cells and resist against the ROS. This study was conducted to evaluate changes in antioxidant enzymes (CAT, GPX, APX) in radish seedlings in response to allelopathic effect of safflower root and shoot residues grown under normal irrigation and drought stress. Safflower allelopathic effect led to an increase in antioxidant enzymes activities. GPX activity increased more than CAT and APX. Radish seedlings exposed to safflower residue grown under drought stress showed more antioxidant enzymes activities. Root residues enhanced the activities of antioxidant enzymes greater than shoot. Seedlings exposed to root residues grown under drought stress had the highest level of antioxidant enzymes activities.

Competitive Ability Effects of Datura stramonium L. and Xanthium strumarium L. on the Development of Maize (Zea mays) Seeds.

The objective of this study was to explore the physical properties of maize seeds in competition with weeds. The basic and complex geometric characteristics of seeds from maize plants, competing with Datura stramonium L. (DS) or Xanthium strumarium (XS) at different weed densities, were studied. It was found that the basic and complex geometric characteristics of maize seeds, such as dimension, aspect ratio, equivalent diameter, sphericity, surface area and volume, were significantly affected by weed competition. The increase in weed density from 0 to 8 plants m2 resulted in an increase in the angle of repose from 27° to 29°, while increasing weed density from 8 to 16 plants m2 caused a diminution of the angle of repose down to 28°. Increasing the density of XS and DS to 16 plants m2 caused a reduction in the maximum 1000 seed weight of maize by 40.3% and 37.4%, respectively. These weed side effects must be considered in the design of industrial equipment for seed cleaning, grading and separation. To our knowledge, this is the first study to consider the effects of weed competition on maize traits, which are important in industrial processing such as seed aeration, sifting and drying.

Salicylic acid affects mycorrhizal features, antioxidant enzyme activities and seed yield of linseed under water-deficit stress in open-field conditions.

The research aims were to study salicylic acid (SA) effects on mycorrhiza [hyphal width (HW), vesicle diameter (VD) and mycorrhizal colonization (MC)] and interaction between them on greenness index (GI), drought tolerance index (DTI), antioxidant enzymes activities, and seed yield of linseed under drought. A factorial experiment was conducted in an open-field place with mycorrhiza [non-inoculation, Funneliformis mosseae (FM), and Rhizoglomus intraradices (RI)], SA (250 µM and non-SA), and irrigation levels [100%, 70%, and 40% field capacity (FC)] as treatments. Severe drought increased VD, MC, superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase activities while decreased GI, DTI, and yield. The RI-linseed had higher MC, GI, SOD, and glutathione reductase (GR) activities, but FM-linseed had greater VD and yield under drought. Inoculated linseed with both mycorrhiza showed a reduction in DTI and yield under SA than non-SA. In RI-linseed, SA increased GI, MC, HW, VD, catalase and GR, but decreased in FM-plants. Mycorrhiza (particularly RI) alleviated drought (40% FC)-caused negative effects on linseed via the improvement of SOD, APX, and GI. Regardless of other treatments, SA had negative effects on HW and VD, but SA effects varied depending on mycorrhizal species so that SA increased HW, VD, and MC in RI. Due to the positive correlation between MC and HW, SA reduces FM colonization by reducing the HW of FM. Totally, SA along with RI species can mitigate the harmful effects of drought and improve tolerance via increasing MC, HW, VD, catalase, peroxidase, and GR activities.