Foliar application of SiO2 nanoparticles to increase shallot production under water stress as an effort to mitigate climate change

Global climate change has resulted in environmental stress which has the potential to reduce the production of various agricultural commodities. One of the reasons for the low production of shallot is because cultivated in land with limited water. An effort to minimize the impact of water stress on shallots is to use SiO2 nanoparticles. This study aims to determine the role of SiO2 nanoparticles to increase production of shallot under water stress. This research was conducted at the greenhouse of the Faculty of Agriculture from December 2022 to March 2023, using randomized block design. The first factor is water stress (80%, 60% and 40% field capacity) and the second factor is the concentration SiO2 nanoparticles (0 g/l, 6 g/l, 12 g/l and 18 g/l). The results showed the water stress treatment had significant effect reduced number of tubers and fresh and dry weight of tubers, the application of SiO2 nanoparticles had significant effect increased the number of tubers and fresh and dry weight of tubers. Interaction of application SiO2 nanoparticles and water stress conditions had a significant effect on increased the number of tubers in the combination of 80% field capacity with SiO2 nanoparticles concentration 12 g/l.


Introduction
The impact of climate change is felt by all sectors of life, but the biggest impact is felt in the agricultural sector.Highly fluctuating climate variations as a whole can threaten the success of food production.A decrease in rain intensity is one of the impacts of climate change which results in drought stress on various agricultural commodities, including shallots which are generally cultivated during the dry season.The yield of tubers in shallot plants is reported to be directly related to the amount of water supply.The decline in shallot production can reach 30% due to drought stress [1 -3].
One way to minimize the impact of drought stress on crop production is to use silica fertilizer.Silica is an abundant mineral element found on earth.Silica can be found in various minerals in abundant quantities in the form of silicic acid.It is very important to maintain Si levels in plants according to their needs so as not to inhibit plant growth potential and prevent a decline or stagnation in production [4].Silica has many positive influences on plant growth and yield.Plants that live in dry conditions will inhibit physiological processes.The use of silica can reduce drought stress by reducing transpiration [4].
The increase in water status in plants that are not irrigated increases significantly with the application of silicon.The application of silicon shows that the water potential in wheat leaves that are stressed by 1302 (2024) 012031 IOP Publishing doi:10.1088/1755-1315/1302/1/012031 2 drought can be maintained compared to without silicon application.The beneficial effects of silicon on plant growth are thought to be related to changes in transpiration.Plants treated with silicon have a thicker cuticle layer and reduced stomatal conduction, which causes the transpiration rate to decrease, which is one mechanism for increasing plant resistance to drought stress [5].
Silicon used in the form of nanoparticles will produce several benefits because nanoparticles have unique physiological properties in plants, a large ratio of surface area and weight, very small size which can accelerate reactions and biochemical activity.Silicon in the form of nanoparticles used can reduce oxidative stress in abiotic and biotic stress conditions in various types of plants.In addition, silicon nanoparticles more easily penetrate the outer layer of cell walls and organelles found in plant cells [6].The aim of the research that has been carried out is to analyze the role of SiO2 nanoparticles in increasing shallot production under water stress conditions as an effort to mitigate global climate change.

Materials and methods
This research was carried out in a Greenhouse located at the Faculty of Agriculture, Universitas Sumatera Utara for five months, namely November 2022 -March 2023.The research design used in this research was a factorial randomized block design consisting of 2 factors, the first factor namely water stress (80% field capacity, 60% field capacity and 40% field capacity) and the second factor namely the concentration SiO2 nanoparticles (0 g/l, 6 g/l, 12 g/l, and 18 g/l).
The study began with land preparation, determination of soil water content and field capacity, nursery, transplanting 40 Day After Plant (DAP), watering based on field capacity according to the treatment one week after transplanting, application of SiO 2 nanoparticles made by ultrasonication method given 15DAP, 30 DAP, 45 DAP.Water is provided every day, pest control uses an insecticide containing the active ingredient deltamethrin at a dose of 2 ml/liter of water, and harvesting is carried out after 14 weeks of planting.
The variables observed in sweet potato production that have been observed are the number of tubers and the fresh and dry weight of the tubers, and the harvest index.Data on observed variables were analyzed using ANOVA (Analysis of Variance).Testing of the influence of significant observed variable data was tested using the Duncan Multiple Range Test (DMRT) at alpha level = 5%.

Results and discussion
Shallots are one of the horticultural crops that are susceptible to drought stress.The shallow roots of shallots make them more susceptible to stress due to water deficit in the planting medium.The response of shallots to water deficit is indicated by a decrease in tuber weight and size [1].The results of the study in Table 1 show that number of tubers of shallot on the effect of water stress and concentration of SiO 2 nanoparticles.------------Tuber----------- The results showed that the number of tubers decreased in direct proportion to the decrease in soil water content.The number of tubers at 40% field capacity (water stress conditions) decreased by 11.50% compared to 80% field capacity (optimal conditions).Stated that if the availability of water in the soil is in a deficit condition, the result is that water, which is the raw material for photosynthesis and a medium for translocating nutrients to the shoot, will be hampered, thereby reducing shallot production [7].
The application of SiO 2 nanoparticles to shallots cultivated in planting media with 80% field capacity was significantly different compared to other treatment combinations (Table 1).The research results of show that in conditions of severe water deficit, the application of SiO 2 nanoparticles has a positive effect related to photosynthesis rates and better stomatal conductance, thus having a positive effect on increasing plant production.------------Tuber----------- Apart from the number of tubers, fresh tuber weight is also significantly influenced by soil water content.The data in Table 2 shows that the water content treatment at 80% field capacity increased by 39.49% compared to the weight of tubers produced by shallot plants treated at 40% field capacity.The data in Table 3 also shows the same trend, where decreasing the water content in the planting medium reduces the dry weight of the tubers.The dry bulb weight of shallots planted under drought stress conditions (40% field capacity) decreased by 41.07% compared to optimal conditions (80% field capacity).
This data shows that shallot production is greatly influenced by the water content of the planting medium, the lower the soil water content, the more shallot production decreases.Research by [7] also shows a decrease in the weight of shallot bulbs under drought conditions.Water stress, whether drought or flooding, can cause stress in shallot plants which need the right amount of water.To produce high quantity and quality yields of shallots, water must be available in sufficient quantities because shallots are very susceptible to water shortages during their life cycle.Stated that a 25% reduction in water capacity under optimal conditions can reduce shallot production, while increasing water use efficiency can be achieved by maintaining soil water content at optimal conditions [8].The results of [9] on shallot cultivation concluded that fresh weight and dry weight of bulbs, bulb diameter, number of tillers and plant weight are influenced by the availability of soil water, limited water availability will reduce the growth and production of shallot bulbs.
Shallot production showed a significant increase with the administration of SiO2 nanoparticles, namely in the fresh weight of the bulbs (Table 2) and the dry weight of the bulbs (Table 3).Providing SiO2 nanoparticles with a concentration of 12 g/l increased the fresh weight of tubers by 99.04% and increased the dry weight of tubers by 107.73% compared to shallot production in plants that were not given SiO 2 nanoparticles.The increase in shallot production is related to the increase in photosynthesis efficiency under water stress conditions by application SiO 2 nanoparticles.The research results of [10] also show that giving silica to garlic plants that are stressed by drought can increase the quantity and quality of the bulbs produced.------------Tuber----------- Stated that giving silica to plants can increase the formation of layers in cell walls, besides that the application of silica nanoparticles affects the water content in the xylem and increases the efficiency of air use which can increase photosynthetic capacity [11].Also stated that in drought stress conditions the application of silica nanoparticles can increase the rate of photosynthesis, stomatal conductance and water potential in hawthorn seedlings.E xplained that the addition of SiO 2 nanoparticles in large quantities through irrigation water can reduce the impact of drought stress on growth as well as several biochemical and physiological characteristics of Prunus mahleb plants [12].In plants experiencing stress, the application of silica can also increase shoot development and chlorophyll content which can support the stability of water potential in leaves and minimize membrane lipid peroxidation.Silica accumulation in plant cells can reduce transpiration and increase photosynthetic activity under drought stress conditions.------------g----------- Harvest index is the ability of plants to allocate biomass or assimilate to reproductive organs.Apart from that, the harvest index is also a value that shows the efficiency and ability of plants physiology t o change dry matter into economically valuable production [13].The data in Table 4 shows that water stress significantly reduces the shallot harvest index.The harvest index decreased by 69.70% in conditions of 40% field capacity when compared to optimal groundwater conditions, namely 80% field capacity.The research results of [8] also show that reducing water supply through irrigation will reduce the shallot harvest index.Stated that the availability of water in the planting media greatly determines the harvest index.In rice plants, the harvest index, which is the proportion of grain production to the total number of parts of the rice plant, really determines harvest yields under water stress conditions.The increase in rice harvest index in the dry season is determined by an increase in soil water status.
The application of SiO 2 nanoparticles significantly increased the onion harvest index.The highest harvest index was produced by shallot plants treated with SiO 2 nanoparticles at a dose of 12 g/l.The research results of [10] also showed an increase in tuber production in shallot plants treated with silica fertilizer.Increased production due to silica fertilization can increase the availability of phosphate for plants.Plants need phosphate for protein formation which increases the photosynthesis process and

Table 1 .
Number of tubers of shallot on water stress effect and concentration of SiO 2 nanoparticles.

Table 2 .
Fresh tuber weight of shallot on water stress effect and concentration of SiO 2 nanoparticles.

Table 3 .
Dry tuber weight of shallot on water stress effect and concentration of SiO2 nanoparticles.
Note: Based on DMRT at the alpha level 5%, numbers followed by different letters show significant differences.

Table 4 .
Harvest index of shallot on water stress effect and concentration of SiO2 Nanoparticles.