No abstract

Seed aging is an important problem in developing countries which seeds stored in inappropriate condition. Delayed germination, reduced normal seedling percentage and changed antioxidant enzymes activity are some indications of aged seeds. Priming is a technique applied before planting and can improve seed characteristics especially under abiotic stress conditions. The main objective of the study was to evaluate aging effect on seed quality and to study the interaction between seed aging and seed priming. A factorial experiment based on completely randomized design with three replicates was conducted. The experimental treatments included cultivar, priming and aging. Results showed that seed aging reduced germination percentage, germination index, seedling length, normal seedling percentage, seedling dry weight, catalase and ascorbate peroxidase activity and increased the germination mean time and electrical conductivity of seeds. The highest germination percentage, germination index, seedling length, normal seedling percentage, seedling dry weight, catalase and ascorbate peroxidase activity and the minimum germination mean time and electrical conductivity of seeds were attained from hydro-priming treatment under non aged condition. Hydro-priming improved aged seeds quality and increased enzymes activity. Therefore, priming is a technique can be applied to improve aged seeds germination and seedling characteristics.

SUMMARYHydroponic Sand Culture (HSC) is a relatively low cost method for potato minituber production. Intensive production under HSC requires applying appropriate growth media composition and plantlet density. An experiment was conducted under HSC in a controlled greenhouse to evaluate growth media composition and plantlet density effect on potato micropropagated plantlets growth, tuberization and concentration of petiole phosphorus and leaf nitrogen. A factorial experiment based on randomized complete block design with 3 replications was used. Studied factors included different 3 growth media composition (fine, medium and coarse) and 2 plantlet density (100 and 150 plantletm-2). Results showed that establishment and biological yield of potato crops grown in coarse composition was significantly higher than the other compositions. Plantlet density had not significant effect on the tuber number per plant and seed sized tuber number per plot. Tuber DW and tuber number per plant was significantly increased in coarse composition of growth media. Fine composition reduced availability of P but not of N, resulting in higher petiole P concentration of crops planted in coarse composition. Coarse composition of growth media was the best composition for potato minituber production in hydroponic sand culture.

Isolation and use of sterile growing media are two important factors in hydroponic production of healthy potato mini-tubers. Sand can be disinfected by solarization, while organic growing media may harbor some pathogenic agents. Under hydroponic condition, number and size of potato tubers are usually controlled by nutritional factors such as nitrogen, phosphorus and pH. The main objective of present study was to find an appropriate combination of N, P and pH (with respect to tuber number) under hydroponic sand culture and to evaluate some physiological traits affected by nutrients and pH. A factorial experiment based on completely randomized design with 4 replications was conducted. The experimental factors included N, P and pH. Some morphological and physiological traits including tuber number, rate of net photosynthesis, concentration of hormones ABA and IAA were studied. Results showed that higher phosphorus concentration for 10 days increased tuber number per plant, but tuberization was not influenced by nitrogen interruption and intermittent reduction of pH. None of N, P and pH affected total nitrogen concentration of potato leaf, stem and tuber. Higher phosphorus concentration increased the level of endogenous ABA and IAA, induced tuberization and thereby increased net photosynthesis rate of potato plants.