Stimulatory effect of different concentrations of fennel, cumin and mint on germination and seed yield of safflower (Carthamus tinctorius L.) in drought stress

Introduction Change any of the environmental factors can basically have effect on processes on plant growth and ultimately on production and operation on crops. Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Seed priming is a presowing treatment that exposes seeds to a certain solution that allows partial hydration but not germination, and redried to original moisture content. Although the germination is not completed, metabolic activities that prepare seeds for radicle protrusion may be initiated during priming. Many evidences have shown seed priming could improve germination and early seedling growth under stress conditions compared to plants grown from untreated seed. Allelochemicals can stimulate the growth at very low concentrations but could inhibit the same at higher concentrations. The stimulatory activity of any compound at lower concentrations is called hormesis. The availability of some chemicals at lower doses could affect the plant hormones and are responsible for growth stimulation, while they might have growth retarding activity at higher doses due to the same or another mechanism of actions. In most of researches negative allelopathic effects surveyed, but little researches had done on posetive allelopathic effects. Materials and methods This investigation had doen in order to survey effect of safflower seeds priming with fennel, cumin and mint water extract (without priming, hydropriming, priming with 1 and 2% concentration) in different irrigation regimes. Investigation had done in laborator as factorial based of completly accidental design and in field as split plot based on complete block design. Results and discussion Based on results of this investigation in greenhouse condition safflower seed priming by medicinal plant extract improved germination and seedling growth and physiologic properties improvement. It seems improvement in safflower seedling growth caused by improvements in safflower seedling physiologic properties. It seems improvements in safflower seedling growth and germination in drought and full irrigation is due to an increase in proteins, gibberellin and carbohydrate content. In field drought decreased safflower seed yield. There were not significant differences between irrigation after 70 mm evaporation from evaporate basin and irrigation after 100 mm evaporation from evaporate basin, but harsher drought decreased safflower yield. Decreasing water from irrigation after 70 mm evaporation from evaporate basin to irrigation after 130 mm evaporation from evaporate basin, decreased grain yield by 38.2 %. But priming with medicinal plant extract caused significant increase in this trait. In this investigation safflower seed priming by all three concentrations of extracts decreased safflower grain yield. But highest increase observed in 1 and 2 percent concentration. This two concentration of medicinal plant extract increased safflower grain yield by 50.9 and 47.6 %. In both mint and cumin higher grain yield observed than fennel, but there were not significant difference between mint and cumin water extract in safflower grain yield. Conclusion Based on results of this investigation safflower seed priming with medicinal plants water extracts not only increases safflower grain yield in full irrigation, it also increases safflower grain yielg in drought condition.