Effects of nettle (Urtica dioica L.) extract on seed germination components and early seedling growth of two wheat cultivars

Abstract
 
Introduction: Nettle with scientific name Urtica dioica L. plant of the family nettle, herbaceous perennial a height of one to two meters, and have high allopathic effect. Many chemicals have allopathic characteristics, have more impact on seeds germination than other stages of development and establishment. Wheat (Triticum aestivum L.) grows in most weather conditions and in a wide range, and sensitive to allelopathic materials.This study aimed to evaluate the effect of nettle extract on seed germination components and seedling growth of two wheat cultivars. Check nettle plant allelopathic potential on the germination characteristics and early growth of wheat were the goals of this research.
Material and methods: A factorial experiment in a completely randomized design with four replications was conducted in the laboratory of the researcher's seed technology University of Shahed in 2014. Experimental factors were two wheat cultivars (Sardary and Azare 2) and three levels of allopathic substance concentration (0, 15 and 30%) (15% = 15 ml aqueous extract in 100 ml of water and 30% = 30 ml aqueous extract in 100 ml of water). For nettle extracts preparation, 20 grams of powdered whole plant collected from the South East of Tehran (Varamin and Pakdasht) was added into the dish containing 200 ml of distilled water for 24 hours on shaker with 110 laps in minutes, and after centrifugation solution to the soluble extracts were prepared. Twenty-five wheat seeds disinfected then replaced in two layers of filter paper (to keep better extract). The petridishes transferred to a germinator with 25 degree centigrade and 70% relative humidity. To calculation of germination percentage and uniformity and time to 5, 10, 50, 90 and 95 percentage of final germination used the Germin program (Soltani et al., 2002).
Results and discussion: According to analysis of variance the most traits were significant for wheat cultivars, nettle extract levels and their interaction effects. Seedling length, radical length, radical dry weight, radical to plumule dry weight ratio and mean germination time were a significant increase with increasing levels of nettle extract, so that the highest mean radical length in treatment combination of 30% of the extract concentration in wheat Sardary cultivar (12.46 cm) and lowest in 15% concentration in Azar2 cultivar (9.56 cm) respectively. The highest germination percentage, germination rate and uniformity of germination was obtained in treatment of control extract of nettle and application extract decreased average of quantities traits, so that germination percentage and germination  rate  in  Azar  2  cultivar was less  than Sardary cultivar. The application of  nettle extract led to increase radical length and it could facilitate access to water for plants in lack of humidity condition. Since of radicle the first part of plant that is directly exposed to allelopathic it is likely that effects of allelopathic higher than other traits. Increasing radical length in effect of nettle extract was may be due to probably increased cell division, increase in the amount of auxin-induced radical growth and involved in respiration. The application of extract increased mean germination time in Sardary cultivar but reduced in Azar 2 cultivar. In general, the application of 30% aqueous extract of nettle causes increase radical and plumule length compared to the non-application in both wheat cultivars (Sardary and Azar 2), respectively. The use of high concentrations of aqueous extract of nettle to reduce of percentage and speed of germination and increase the time needed for seed germination. The results showed that have inhibitory potential nettle extract residues on germination of wheat varieties (Azar 2 and Sardary).