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Agricultural and Environmental Chemistry
Promoting Potato Seed Sprouting using an Amphiphilic Nanocomposite Lihong Zhang, Guilong Zhang, Zhangyu Dai, Po Bian, Naiqin Zhong, Yuanyuan Zhang, Dongqing Cai, and Zhengyan Wu J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b03994 • Publication Date (Web): 29 Aug 2018 Downloaded from http://pubs.acs.org on September 1, 2018
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Promoting Potato Seed Sprouting using an Amphiphilic
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Nanocomposite
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Lihong Zhang,†,§ Guilong Zhang,†,‡ Zhangyu Dai,†,§ Po Bian,†,‡ Naiqin Zhong,#
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Yuanyuan Zhang,||,* Dongqing Cai,†,‡,* Zhengyan Wu,†,‡,*
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†
Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei
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Institutes of Physical Science, Chinese Academy of Sciences, 350 Shushanhu Road,
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Hefei 230031, People’s Republic of China
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§
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People’s Republic of China
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||
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People’s Republic of China
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#
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West Road, Chinese Academy of Sciences, Beijing 100101, People’s Republic of
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China
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University of Science and Technology of China, No. 96 Jinzhai Road, Hefei 230026,
School of life Science, Anhui Medical University, No.81 Meishan Road, Hefei 230032,
State Key Laboratory of Plant Genomics, Institute of Microbiology, No. 1 Beichen
‡
Key Laboratory of Environmental Toxicology and Pollution Control Technology of
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Anhui Province, Hefei Institutes of Physical Science, Chinese Academy of Sciences,
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350 Shushanhu Road, Hefei 230031, People’s Republic of China
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* Y.Z. Email:
[email protected].
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*D.C. Email:
[email protected].
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*Z.W. Email:
[email protected].
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ABSTRACT: Most potato tubers were used as seeds and sprouted relatively slowly
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in soil, greatly influencing potato production. To solve this problem, an amphiphilic
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nanocomposite was fabricated by loading hydrophobic silica (H-SiO2) in hydrophilic
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attapulgite nest-like and used as a nano presprouting agent (NPA). This technology
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could conveniently adjust the occupation area ratio of water and air (OARWA) on
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potatoes surface. NPA could endow potatoes with an appropriate OARWA and thus
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effectively accelerate sprouting. Additionally, NPA greatly decreased soil bulk density,
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facilitated earthworms growth, promoted potatoes growth, and increased yield by
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14.1%. Besides, NPA did not pass through potato skin and mainly existed on the
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surface of potatoes. Importantly, NPA showed tiny influence on the viability of fish
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and nematodes, demonstrating a good biosafety. Therefore, this work provides a
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promising presprouting approach for potatoes, which may have a potential application
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prospect in ensuring food supply.
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KEYWORDS: potato seed, hydrophobic nano silica, attapulgite, presprouting,
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amphiphilic
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INTRODUCTION
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Potato is one of the top four crops and an excellent staple food in the world due to its
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high nutritional value.1 Potato tubers were used as seeds whose sprouting plays a key
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role in maintaining its yield.2-4 The sprouting speed is closely determined by water
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amount on potato surface and respiratory intensity, which is related to the occupation
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area ratio of water and air (OARWA) on potato surface.5,6 However, as for a majority
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of varieties, potato seeds possess relatively smooth surface, thus a low water-retaining
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capacity (WRC). Additionally, because of the hydrophilic surface of potatoes, water
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tends to occupy almost all the surface area, which is unfavorable for the respiration.
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Therefore, most potato seeds possess low sprouting speed in soil.7 This problem has
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become one of the dominant negative factors for potato production and sustainable
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development of potato-related industries.8 Hence, it is essential to control the
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hydrophilcity of potato surface to obtain an appropriate OARWA and thus promote the
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sprouting and yield.
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During the past few decades, a great many of methods of promoting potato
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sprouting have been developed including physical and chemical aspects. Therein,
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physical method mainly refers to thermal treatment of potatoes, and chemical method
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mainly refers to treatment of potatoes using chemicals including carbon disulphide,
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gibberellic acid, cytokinin, bromoethane, phenylurea, nitroguanidine cytokinins and
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so on.9-13 Although these methods could promote potato sprouting to certain extent,
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there are some defects limiting their huge applications. As for physical method,
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thermal treatment shows high cost and consumption of time and labor.14,15 As for
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chemical methods, carbon disulphide generally displays short duration;16 organic
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matters (gibberellic acid, cytokinin, bromoethane, phenylurea, nitroguanidine
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cytokinins and so on) display relatively low stability and tend to induce thin and 3
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fragile sprouts, and some of them are not environmentally friendly.17 Noteworthily,
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these methods mainly adjust the temperature and sprouting-related enzyme activity to
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promote potato sprouting. While they cannot control the OARWA. Hence, it is
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necessary to develop simple, low-cost, and environmentally friendly methods to
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control OARWA and thus accelerate potato sprouting.
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Attapulgite (Mg,Al)4(Si)8(O,OH,H2O)26·nH2O), a kind of rod-shaped nanoclay
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with advantages of abundant supply, environmental friendliness, low cost, and high
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stability, has been widely used as adsorbent, insulation, paint, etc.18-21 Because of the
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abundant –OH on the rods surface, attapulgite possesses a hydrophilic property and is
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suitable to be used as water-retaining material.22-26 Thus, attapulgite can be a potential
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candidate for nano presprouting agent (NPA) of potatoes. However, because of the
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nano scale effect and high surface activity, attapulgite rods naturally tend to aggregate
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with each other to form bunches, which is unfavorable for the exposure of –OH and
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water adsorption ability.27,28 Hence, it is important to improve the dispersion of
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attapulgite, increase surface group amount, and the WRC.29,30 More importantly,
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attapulgite is not an amphiphilic substance and can hardly control the OARWA on
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potato surface. Therefore, it is necessary to combine a hydrophobic substance with
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attapulgite to obtain an amphiphilic nanocomposite which can adjust OARWA on
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potato surface.
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In this work, hydrophobic silica (H-SiO2) was loaded on the surface of
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attapulgite rods to obtain an amphiphilic nanocomposite (attapulgite/H-SiO2) with
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nest-like structure. Subsequently, attapulgite/H-SiO2 was used as a NPA whose effects
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on water-retaining, OARWA, potato sprouting, and yield were investigated. In
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addition, the interactions among potatoes, attapulgite, and H-SiO2 were analyzed to
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elucidate
the
mechanism
of
this
technology.
Besides,
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biosafety
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attapulgite/H-SiO2 was studied on nematode and fish. This work provides a facile,
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low-cost, and environment-friendly approach for presprouting of potatoes, which
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might have a potential application prospect in potato production.
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MATERIALS AND METHODS
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Materials. Disease-free miniature potatoes (E-Malingshu No. 5, diameter=35
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mm, weight of each potato=20-35 g) were purchased from Chunsemanyuan Co.
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(Hubei, China). attapulgite powder (300 mesh) was purchased from Mingmei Co., Ltd.
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(Anhui, China). Other chemicals of analytical reagent grade were provided by
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Sinopharm Chemical Reagent Company (Shanghai, China). Deionized water was used
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in all the experiments except pot tests. Soil (texture of calcareous soil, pH of 8.1,
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carbonate content of 7 mmol/L, sand content of 2%, organic matter of 6.0 g/kg) used
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in pot experiments was taken from Dongpu Island (Hefei, China). Adult earthworms
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(E.fetida, length of 7-13 cm, weight of 0.4-1.0 g) with well-developed clitellum were
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purchased from Earthworm Breeder Company (Tianjin, China). Adult zebrafish
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(Danio rerio, mean mass of 0.52±0.1 g) of both sexes were purchased from China
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Zebrafish Resource Center, China. The respiratory intensity of potato was measured
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by acid-base titration method.
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Preparation of attapulgite/H-SiO2. Silica (4 g) was added to 40 mL of ethanol
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and the resulting system was stirred (500 rpm) for 5 min. Then 1 mL of amino silicon
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oil was added to the system dropwisely and the resulting suspension was stirred (500
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rpm) for 30 min at room temperature. After that, the resulting suspension was dried at
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60oC for 24 h to obtain H-SiO2 powder (100-200 mesh) after grinding. attapulgite (4 g)
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was dispersed in 40 mL of ethanol, then H-SiO2 (1, 2, or 3 g) was added to the system
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which was then stirred (500 rpm) for 40 min. Thereafter, the system was dried at 60oC
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to obtain attapulgite/H-SiO2 powder (200-300 mesh) with different weight ratios 5
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(Wattapulgite/WH-SiO2=4:1, 4:2, or 4:3) after grinding. The optimal attapulgite/H-SiO2
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with Wattapulgite:WH-SiO2 of 4:2 was obtained through sprouting and pot experiments and
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designated as NPA.
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Water retention performance investigation. 10 potatoes were immersed in
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attapulgite/H-SiO2 aqueous solution (50 mL, 60 g/L) or water (50 mL) for 15 s one by
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one. Then they were taken out and placed in air at room temperature. The weight of
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each potato was measured every 5 minutes, and the water-retention ratio (WRR) of
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attapulgite/H-SiO2 on potato surface was calculated according to equation 1:31,32
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WRR= [(WC0−WCt) − (W0−Wt)]/(WC0−WCt)×100%
(1)
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where WC0 and WCt were initial and resulting (at time t) weights of potato after taking
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out from water. W0 and Wt were initial and resulting (at time t) weights of potato after
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taking out from attapulgite/H-SiO2 aqueous solution.
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Similarly, the WRR of attapulgite/H-SiO2 in water (20 g/L, 20 mL) in a beaker
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(100 mL) was also investigated compared with water (20 mL) alone. The weight of
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the system was measured every 5 minutes, and the WRR of attapulgite/H-SiO2 in
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water was calculated according to equation 1, where WC0 and WCt were initial and
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resulting weights of water at time t respectively. W0 and Wt were initial and resulting
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weights of attapulgite/H-SiO2 aqueous solution at time t. All tests were carried out in
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triplicate.
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Effect of attapulgite/H-SiO2 on potatoes sprouting in air. attapulgite/H-SiO2
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with a certain amount was added to 40 mL of ethanol to obtain attapulgite/H-SiO2
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ethanol solution. After that, 18 potatoes were immersed in the solution for 15 s one by
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one and transferred to a greenhouse (humidity of 70%, 25oC). The numbers of long
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(≥5 mm), short (
