Physiological, Morphological Changes and Storage Root Yield of Sweetpotato [Ipomoea batatas (L.) Lam.] under PEG-Induced Water Stress

Abstract

Sweetpotato is an important tuberous root crop rich in nutrients such as vitamins and carbohydrates, and can grow well in arid regions with less water consuming crop. The aim of this research was to evaluate the storage root yields, physiological, biochemical and morphological traits in sweetpotato cv. 'Japanese Yellow' subjected to polyethylene glycol (PEG)-induced water deficit. At harvest (4 months after planting) the number of storage roots per plant and storage root fresh weight in sweetpotato treated with 5% PEG (−0.54 MPa) in nutrient solution of hydroponic culture declined by 20.0% and 47.4% compared to the control without PEG, respectively. Leaf area and leaf dry weight significantly decreased by 85.6% and 95.3%, respectively when exposed to water deficit stress. Sucrose content (114.7 mg g -1 dry weight; DW) in storage roots of sweetpotato grown under PEG-induced water deficit conditions was enriched by 2.2 fold of control (52.5 mg g -1 DW) and was greater than in storage roots derived from soil culture (70.3 mg g -1 DW). Total soluble sugar in the root and storage root tissues was enriched and may play a key role as osmotic adjustment (OA) in PEG-induced water stressed plants. Free proline and sucrose contents were also dominated in the leaf tissues to maintain the leaf osmotic potential in water stressed plants. In addition, chlorophyll degradation, chlorophyll fluorescence diminution and stomatal closure were found in plants grown under PEG-induced water deficit conditions, leading to reduction in net photosynthetic rate (Pn) and subsequently lesser amounts of glucose and fructose contents in the leaf tissues. Sucrose and free proline in the roots of sweetpotato play a key role as major osmotic adjustment when subjected to PEG-induced water deficit condition. Basic knowledge gained from this research will further be investigated the drought defense mechanism in sweetpotato via osmoregulation system.

Physiological and Biochemical Responses of Two Herbaceous Peony Cultivars to Drought Stress

“…As shown in Fig. 4, the increasing trends of soluble sugar and proline contents observed in both herbaceous peony cultivars under drought stress mirror previous findings of some tuberous root plants such as Dahlia pinnata (Fan et al, 2011), Ipomoea batatas (Yooyongwech et al, 2017), and P. suffruticosa 'Luo Yang Hong' and 'Hu Hong' (Kong et al, 2011), the latter using potted plants with four levels of SMC (100%, 75% as CK, 50%, and 25%). However, the variation in soluble protein content of this study was not unanimous.…”

Variation in productivity of Ipomoea batatas at various rates of nitrogen fertilization

“…This may be associated with root system length (Borawska-Jarmułowicz et al, 2014). A longer root system can be advantageous in the case of drought stress in the deeper soil layers, as confirmed by the study Yooyongwech et al (2017).…”

“…Results of Kingori et al (2016) suggest that nitrogen fertilization influences the physiological status of the I. batatas plants, including leaf expansion ability, stomatal conductance and chlorophyll content. A study by Brestic and Zivcak (2013) and Yooyongwech et al (2017) has revealed that photosynthesis is a metabolic process that is particularly sensitive to many stress factors. A frequent component of the so-called multistress is fertilizer stress which occurs when photosynthetic pigments absorb too much photosynthetically active radiation (PAR) energy in relation to the capacity to convert it into chemical energy during photosynthesis (Brestic, Zivcak, 2013).…”

“…The experiment was set up in a randomized block design in three replicates on a fawn soil, produced from strong clay loam (WRB, 2014). The tested physical and chemical properties of soils are given in Table 1.…”

“…Chlorophyll is excited by a light wave, not less than 620 nm, which comes from the source of light in a fluorometer. The induced fluorescence of the leaf is received by a detector, also equipped with an appropriate filter that cuts off far-red fluorescence (Kalaji et al, 2016 b;Yooyongwech et al, 2017). The measurement is made in the absence of external light.…”