Effects Of Lemon Juice, Led Light And Peg-8000 On Plant Growth And Tuberization In Potato

Potato(Solanum tuberosum L.) is one of the most important food crops with high nutritional value and broad adaptability. In recent years, tissue culture technique has provided an effective tool to complement conventional plant breeding. And the growth regulators are very important for plantlets growth but, due to the high cost of the industrial growth regulators, they cannot meet the requirement in some countries. Thus it is important to discover an alternative growth regulator with low cost. The culture potato plantlets growth in vitro is affected directly by the light intensity, but unfortunately, there are no clear reports on the optimum levels of the light spectrum under light intensity(collectively) at the potato plantlets growth stages of in vitro culture. In addition, the problem of water shortage is very acute in some countries. Early growth and tuber formation require large amounts of water, and the short periods of water shortage can reduce tuber production and tuber quality. In this study, three experiments are carried out to solve these problems: firstly, lemon juice is used as an alternative growth regulator; secondly, the light spectrum and light intensity on plantlets of potato in vitro are influenced; lastly, the drought tolerance on potato varieties is studied and different concentrations of Polyethylene Glycol(PEG-8000) are used for plantlets treatment. The main results are summarized as follows: 1. Effects of lemon juice on plantlets growth for varieties of potatoDifferent concentrations of lemon juice(1, 2, and 3 ml/L) and three varieties are used in this study. Seedlings growth has been observed after one month since they were cultured. It is very clear that 3 ml/L of lemon juice is optimum for Zhongshu 20 variety compared to the control on the traits, including plant length, root length, number of leafs, node number, and wet weight amounted(10.06 cm, 11.36 cm, 12.62, 10.68 and 125.02 mg, respectively). However, the number of roots and leaf size of potato seedlings reach highest at the 2 ml/L of lemon juice(6.13 and 4.33cm2). The response to lemon juice as an alternative growth regulator provides insights into the morphological traits which can be used for seedlings’ growth evaluation in tissue culture and illustrating the effectiveness of the proposed concentrations of lemon juice to MS media to improve certain morphological parameters of seedlings selection and validation. 2. Effects of different photoperiod combinations in-vitro on the plantlets growth of potatoTwo studies on three varieties of potato in vitro have been implemented. Firstly, the effect of the illumination spectrum on the morphogenesis of potato plantlets growth in vitro has been studied by using four groups(9:1:0),(8:1:1),(7:2:1) and(6:3:1) for(red: blue: white, respectively), of the light-emitting diode(LED) under four levels of the light intensity(1500, 2000, 2500, and 3000 lux). Secondly, the effect of different four levels of white fluorescent tube lamp intensity(1500, 2000, 2500, and 3000 lux) on plantlets of potatoes has also been studied. In this investigation, it is observed that varieties respond to all photoperiod combinations in different ways and improve certain morphological characteristics of plantlets. However, seedlings displayed a significant(p < 0.05) increase in the node number, branch number, leaf size and number of leafs(which were 9.10, 3.43 cm2, 4.70 and 20.66, respectively), has been mapped on the spectral combination(red: blue: white, 6:3:1) with 2000 lux and 3000 lux intensity. The maximum rate of the plant length and the number of roots(10.23 cm and 6.46) have also been obtained in(red: blue: white, 9:1:0) spectral combination with 2000 lux intensity. Furthermore, under white fluorescent lamps, the light intensity level at 2000 lux shows a significant(p < 0.05) increase in the length of roots and in the number of roots, number of branches, number of leafs and wet weight amounted(9.80 cm, 6.20, 2.13, 17.28 and 232.75 mg, respectively). 3. Evaluation of drought tolerance response in varieties of potato under greenhouse conditionsPotato varieties with drought tolerance would help to ameliorate the adverse effect of drought on potato yield. In this investigation, two experiments are carried out under greenhouse conditions for PEG-induced water stress. In the first part, seedlings are treated with Polyethylene Glycol(PEG-8000) at different concentrations(0%, 10%, 15% and 20%) in two consecutive stages of growth of three varieties. Phenotypic data(photosynthesis Fv/m and Yield, plant height, leaf number, leaf area, plant fresh weight, plant dry weight, root length, root fresh weight, root dry weight, number of tubers, a tuber wet weight and tuber dry weight) show a significant decrease under 20% concentration of PEG. In the second part which aims to select potato genotypes with tolerance to drought stress through in vermiculite, the 20% concentration of PEG-8000 is used to treat 20 varieties of potato. The highest values are found in most morphological traits such as the leaf number, leaf area, root length, plant fresh weight, plant dry weight, root fresh weight, and root dry weight at varieties(Zhongshu 19 variety and Zhongshu 18 variety). In two stages, significantly higher number of tuber is measured in variety Jinghu 2 under PEG stress. The results achieved in this study can lead to potato genotype identification for drought tolerance in greenhouse.