Effect of chitosan application time on seedlings of various rambutan varieties (Nephelium lappaceum L.)

Chitosan is a compound obtained from the extraction of marine crustaceans. Chitosan has an essential role in agriculture as a plant growth promoter. Research on the effect of chitosan application time on seedlings of various rambutan varieties aims to determine if there is an effect of differences in chitosan application time and varieties on the growth of rambutan seedlings. The research was conducted in March-June 2022 at the Screen House of the Faculty of Agriculture, Sebelas Maret University using a Randomize Completely Block Design (RCBD) with 2 factors. The first factor was aceh, binjai, and rapiah variety. The second factor is without chitosan application, morning chitosan application, afternoon chitosan application, morning and afternoon chitosan application. Chitosan application was done weekly with a concentration of 2 ml/L. The results showed that chitosan application time in the morning produces the highest plant height in all rambutan varieties. Rapiah gave the best results in plant height and root length, binjai gave the highest results in stem diameter and leaf area, while aceh variety gave the highest results in the number of leaves.


Introduction
Rambutan trees are straightforward to find in Indonesia.Still, most people only focus on utilising the sweet fruit.In contrast, rambutan seeds have not been utilized properly even though rambutan seeds have a fatty acid content of 37-43%, which can be used as an ingredient in making biodiesel [1].The increasing use of biodiesel must be balanced with abundant raw materials, namely rambutan seeds.Rambutan growth optimisation is needed, one of which is using chitosan.Chitosan (C6H11NO4)n is an organic compound derived from chitin, a polysaccharide usually found in the exoskeleton of Crustaceae sp.such as crabs, shrimps, and lobsters are obtained through a deacetylation process by reacting with high alkali concentrations for a long time and at high temperatures [2].Chitosan has a myriad of benefits in agriculture, especially in plant growth and development because it contains various phytohormones such as auxins (Indole Acetic Acid), gibberellins (GA3, GA5, GA7), and cytokinins (kinetin and zeatin) [3].Growth hormones (IAA, kinetin, zeatin, gibberellin) contained in chitosan can spur the growth and development of corn plants [4].Applying chitosan to the leaves can increase the vegetative growth stage and plant production yields [5].Chitosan is effectively absorbed in plant leaves, providing amino acids that enhance various metabolic processes and plant growth [6].The application of chitosan affects plant height, number of leaves, and seed weight of Grobogan soybean varieties which can increase yields by 61.64% compared to soybeans without chitosan treatment.Based on this explanation, a study was conducted to determine the effect of chitosan application on rambutan seedlings when applied at different times and with different types of rambutan.

Materials and methods
This research was conducted at the Screen House of the Faculty of Agriculture, Sebelas Maret University Surakarta in March-June 2022.The tools and materials used in this research activity include rambutan seeds, planting media, chitosan, water, fungicides, measuring cups, scales, and hand sprayers.The research stages carried out were planting preparation which was carried out by mixing soil with compost in a ratio of 1: 1, planting rambutan seeds,and then applying chitosan.The concentration of chitosan used was 2 ml/L and applied once a week.Measurements were taken once a week and 12 weeks after planting.
The research method used was a Randomized Completely Block Design (RCBD) with 2 factors.The first factor is variety, the aceh, binjai, and rapiah.The second factor is application time, without chitosan application, morning chitosan application, afternoon chitosan application, morning and afternoon chitosan application.The experiment was carried out in three sets, each consisting of 12 units, resulting in a total of 36 experimental units.The observed variables included plant height, stem diameter, number of leaves, leaf area, and root length.The results were analyzed using Analysis of Variance (ANOVA) at the 5% level if significantly different followed by Duncan's Multiple Range Test (DMRT).

Plant height
The variety and time of chitosan application significantly affect plant height.Based on the DMRT test at the 5% level (Table 1) rapiah varieties showed significantly different results with aceh, but not significantly different from binjai at the end of observation (12 WAP).The rapiah variety treatment gave the highest average yield at 12 WAP, which was 20.09 cm.This height difference is due to genetic traits that have different characteristics in plant height are not only influenced by environmental factors, but also by genetic factors, when environmental conditions are the same for all genotypes, genetic factors play a more significant role in differences in plant height [7].According to the observation results, the plant height treated with chitosan in the morning showed significantly better results than the other treatments.The highest plant height of 20.66 cm was observed with the chitosan application in the morning.Applying chitosan in the morning allows it to seep deep into the soil without the risk of excessive evaporation, besides that, it can also provide sufficient materials and nutrients for plants to carry out photosynthesis.Stomata influence photosynthesis because they act as a place to exchange carbon dioxide, oxygen, and water vapor [8].The stomata are fully open in the morning, partially open during the day to reduce evaporation, and more open in the afternoon [9].In contrast to the afternoon, plants get shorter irradiation time, mainly when the research is conducted in the rainy season with an average rainfall of 14 mm.Rain often falls in the afternoon, making the light received by plants less, so chitosan applied in the afternoon becomes less effective.

Stem diameter
Based on the variance analysis, the results of application time and the interaction between varieties and chitosan application time did not significantly affect the increase in plant diameter.Rambutan varieties have a real effect on rambutan diameter.Based on the results of the DMRT further test at the 5% level (Table 2) shows that the binjai variety has an average stem diameter that is significantly different from aceh.Binjai has the largest average diameter at the end of the observation which is 3.28 cm, while aceh owns the smallest stem diameter with an average of 2.76 cm.Rapiah has an average stem diameter of 3.11 cm at the end of the observation.The diameter of rambutan at 1 WAP shows results that are not much different because the provision of chitosan has not yet affected stem diameter growth.Stem diameter is included in secondary growth stem diameter growth when the need for photosynthesis products for respiration, root growth, leaves, and plant height has been fulfilled.Chitosan application time gives a real effect at the age of 1 WAP.The absence of the effect of chitosan use on stem diameter growth is likely due to the dose of chitosan used which is too small, so only genetic factors of each rambutan variety affect stem diameter growth.The stem diameter increased due to adequate nutrient availability, promoting plant growth [10].The higher rate of photosynthesis indicates good growth.Phloem translocates carbohydrates to stimulate secondary growth, resulting in wider stem diameter.

Number of leaves
According to the analysis of variance, the variety and time of chitosan application and their interaction gave no significant results on the number of rambutan leaves.The relatively same number of leaves is because there is no competition in utilizing sunlight, nutrients, and water [11].The results of measuring the height gradient of rambutan can be seen in figure 1 below.

Figure 1. Effect of variety and application time on the number of rambutan leaves
The highest number of leaves at the end of observation was produced by Aceh, with chitosan application time in the morning and an average number of leaves of 9.67 strands.The lowest number of leaves was produced by binjai without chitosan application with an average number of leaves of 6 strands.Applying chitosan in the morning produces the highest average number of leaves in the aceh and rapiah varieties, which are 9.67 and 7.67 respectively.In contrast, in the binjai variety, most leaves are produced by chitosan application in the afternoon with an average number of leaves of 8.33.All varieties treated with chitosan watering either in the morning, afternoon, or morning and afternoon produce more leaves than without chitosan application.Chitosan can be used as a coating for fertilizers and other nutrients to control their release, increase shelf life, and prevent waste.The N element in chitosan will also affect plant cell division and leaf growth [12].The N element enhances plant growth by providing water and stimulating new leaf production from the stem and older leaves lateral buds.Good absorption of N elements results in a more significant number of leaves [13].

Leaf area
The analysis of variance revealed no significant effect of using rambutan varieties or chitosan application time, nor was there any interaction between the two on plant leaf area.This is because rambutan leaves do not have significant differences in anatomical structure between cultivars [14].The treatment with the highest leaf area is binjai with chitosan application time in the morning with an area of 20,08 cm².This result was not much different from rapiah treatment with chitosan application time in the afternoon with an area of 19,81 cm².The aceh treatment produced the smallest leaf area with chitosan application time in the morning and afternoon with an area of 10,76 cm².Similar results were stated by previous research on pachira plants, with the lowest yield of leaf area with 1% of chitosan in the morning and afternoon.The time of chitosan administration divided into morning and evening produces the lowest leaf area because the dose used, if given half and half, makes the chitosan not absorbed optimally [15].

Root length
According to the experiment, neither the Rambutan variety nor the chitosan application time had any significant effect on root length.The interaction between the Rambutan variety and chitosan application time also had no significant effect on root length.The significance values obtained for all the factors were 0.884, 0.314, and 0.816, respectively.

Figure 3. Effect of variety and application time on root length
Based on Figure 5, chitosan application in rapiah treatment with chitosan application time in the morning and afternoon produces the highest root length of 10.10 cm.The treatment that gives the lowest results is rapiah treatment with chitosan application time in the afternoon with a root length of 6 cm.Applying chitosan in the morning and afternoon increased the root length of the binjai and rapiah varieties, while the aceh variety treatment without chitosan application resulted in the highest root growth compared to the plants treated with chitosan.The hydrophilic properties of chitosan can help absorb water in soil, which is crucial for effective plant growth in the presence of external factors like water and nitrogen elements [16].Root growth is influenced by water availability because roots will move according to water availability [17].Plants that experience water shortages can take maximum water with the expansion and depth of the root system increasing [18].

Fresh weight
Variety gives a real influence on the fresh weight.After conducting further testing with DMRT at a 95% confidence level, it was found that there were no significant differences between the rapiah and aceh varieties.Both varieties had a fresh weight of 4.25 and 4.14 grams respectively.However, the binjai variety was significantly different from the other two and had the lowest fresh weight, averaging at 3.3 grams.Chitosan application time and the interaction between varieties and chitosan application time did not give a significant effect on the fresh weight.Based on figure 4 the highest fresh weight was produced by aceh treatment with chitosan application time in the morning with a weight of 4.77 grams.The lowest result was shown by the Binjai treatment with chitosan application time in the afternoon with a weight of 2.37 grams.Chitosan contains around 9-10% potassium and nitrogen.These compounds are essential macronutrients for plants and play a crucial role in their growth [19].The presence of potassium and nitrogen is closely associated with the increase in the size and number of chloroplasts in the leaves.This, in turn, leads to an increase in the number of cells per unit area in the leaves [20].The more the number of leaves, the fresh weight of the bran will also increase.The more the number of leaves, the more photosynthesis that produces assimilate will affect the fresh weight.

Conclusion
The most effective application time is in the morning, producing the highest plant height in all rambutan varieties.Rapiah achieved the best results in terms of plant height and root length, binjai had the highest results in stem diameter and leaf area, while cceh variety had the highest results in the number of leaves and fresh weight.

Figure 4 .
Figure 4. Effect of variety and application time on fresh weight control morning afternoon morning and afternoon

Table 1 .
Effect of variety and time of chitosan application on rambutan height

Table 2 .
Effect of variety and time of chitosan application on rambutan stem diameter