Abstract
This study, consisting of two independent experiments, was conducted to optimize presowing guava seed treatments and evaluate the optimized treatments in improving germination and seedling growth of guava under heat and osmotic stresses. In the first experiment, seeds of guava cultivar White Flesh Local I were soaked in water, gibberellic acid (GA3) (0.05 and 0.1%), hydrochloric acid (HCl) (5 and 10%) and sulfuric acid (H2SO4) (5 and 10%) for 24 and 48 h (for water and GA3), and 2 and 5 min (for HCl and H2SO4). Seed soaking (priming) with GA3 (0.1%, at 48 h) and HCl (10%, 2 min) were the most effective treatments to improve seed germination and early seed growth of guava and were used in the second experiment. In the second experiment, treated and untreated seeds were sown in plastic boxes between two layers of filter papers maintained at osmotic potentials of 0, -1.5 and -3 MPa. The germination boxes were incubated at optimal (25 °C) and higher (32 °C) temperatures. Germination was significantly suppressed at a higher temperature and with an increase in the osmotic potential. However, seed treatments with GA3 and HCl were effective to improve the germination and seedling growth of guava under both temperature and osmotic stresses. In conclusion, chemical and hormonal seed treatments may help improve the seed germination and seedling growth of guava under heat and osmotic stresses by modulation of antioxidant enzymes and leaf proline. Seed treatment with GA3 (0.1%, 48 h) was the most effective in this regard.
Highlights
Guava (Psidium guajava L.), from the Myrtaceae family, is a fruit crop in tropical and subtropical regions, of economic and nutritional importance, and its fruit is used as fresh food and in processing industries to prepare fruit juices, compotes, essential oils, and powders
Seeds of guava cultivar White Flesh Local I were soaked in water, gibberellic acid (GA3) (0.05 and 0.1%), hydrochloric acid (HCl) (5 and 10%) and sulfuric acid (H2SO4) (5 and 10%) for 24 and 48 h, and 2 and 5 min
The highest germination percentage (93.97%) and germination rate (21.1) were observed with seed priming by GA3 (0.1% for 48 h), followed by seed soaking in HCl (10% for 2 min) (Table 1)
Summary
Guava (Psidium guajava L.), from the Myrtaceae family, is a fruit crop in tropical and subtropical regions, of economic and nutritional importance, and its fruit is used as fresh food and in processing industries to prepare fruit juices, compotes, essential oils, and powders. In addition to its specific taste and aroma guava fruits are rich in vitamin C, pectin, and minerals. In Iran, guava is cultivated in many tropical provinces such as Hormozgan and Sistan and Baluchestan (Khosravi et al 2018). It is propagated through cuttings, stooling, grafting, or air layering, propagation through seeds is the most common method in Iran (and in some other regions) (Shekafandeh and Khoushkhoui 2005). Propagation through seeds is required in breeding and genetic improvement programs and to produce rootstocks (Kalyani et al 2014)
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