The growth character of sago palm based on differences in time of trunk formation

This study aimed to (1) characterized sago palms with different trunk formation times; (2) studied the growth characteristics related to the diameter of the sago trunk. This research was conducted at the Sago Cultivation Experimental Site located in Pengkajoang Village, West Malangke District, North LuwuRegency.Thegrowth characters studied were number of leaves, trunk diameter, leaf length,petiole length, tree height,rachis length, number of suckers, length of the most extended leaflets, number of leaflets and the width of broadest leaflets. A paired T-Test was used to analyze the average of three variables between sago-forming trunks at 3 years, 3.5 years, and 4 years after transplanting. In addition to correlation analysis, variables were compared based on their relationships.The sago palm that formed the trunk at 3 years after transplanting had the highest number of leaves (20 strands), 3.5 years (17 strands), and 4 years (16 strands). Conversely, sago palms that form trunks 4 years after transplanting have the widest leaflets(7.44 cm), 3.5 years (6.04 cm) and 3 years (6.52 cm). Based on correlation analysis and path analysis, it is known that the number of leaves, tree height and rachis length are characteristics of sago palm growth which have a significant effect on the formation of trunk diameter.


Introduction
Sago (Metroxylon sago) is a plant that produces starch and stores it in trunks with a growth and development period of 11-12 years.Until now, sago is known to have the highest starch yield per unit area per unit of time.Sago can produce 25 tons/ha/year of starch, while rice only produces 6 tons/ha/year of starch [1].
As one of the regions suspected of being the origin of sago plants, Indonesia has excellent opportunities for sagodevelopment.More than 95% of the world's sago plants are only found in Indonesia, Malaysia and Papua New Guinea.Indonesia is the most blessed country because around 50% of the world's sago plants are found in Indonesia [2].
Sago plants have enormous potential to be developed as a food source and industrial raw materials.This ecological character of sago makes it a unique crop because it is different from other food crops The potential of sago as food and non-food ingredients causes the need and demand for sago to increase, so it is necessary to increase production.Nowadays,Indonesia still relies on sago trees that grow naturally [3].It is feared that the growth of the natural sago population will not be able to adjust the logging rate to support sago demand.
Development of sago faces many challenges.. Long harvesting time, price competition, limited processed products, popularity, and the assumption that sago is food for Easterners cause people to be less interested in cultivating sago.As the centreof spreading sago in the world, Indonesia should be ready with sago cultivation techniques from seeding to harvesting.
On a 2 ha land belonging to a collaboration with Ehime Japan University, Hasanuddin University in North Luwu district, sago was planted with a spacing of 10 m x 10 m, according to the recommended spacing [4].In the 4th year after planting, almost all of the sago plants planted have entered the trunk formation stage.Trunk formation is closely related to the start of filling starch in the trunk as the plant's main product.This makes the size oftrunk diameter important in estimating yield potential.
After three years of planting, 50% of the sago trees have entered the trunk formation stage.The start of the trunk formation stage on other sago plants continues until the fifth year after transplanting.The time difference that occurs in forming trunks isessential to be studied.This research will study the growth characteristics of sago plants based on differences in the age of trunk formation.

Materials and methods
In the first year of planting, 157 sago seeds were planted at a distance of 10 x 10 meters.One year after planting, only 91 sago plants survived (Table 1).Cleaning of weeds in sago fields is carried out once a month.There was no fertilization activity and a reduction in the number of tillers.Observations were made every 2 months.In this study, three groups of sago plantsdifferentiated based on the age of trunk formation after transplanting tillers.There were 15 plant samples with 5 plant samples each in the age group of 3 years, 3.5 years and 4 years after transplanting tillers.
This study used a paired T-test to compare the average values of each variable in each group with different times forming trunks.Correlation analysis and path analysis were carried out to study the influence relationship of each growth character on trunk formation.
The trunk and leaf characters of sago plants were measured directly in the field (figure 1).Leaf character is considered to describe the quality of sago growth [5].Some of the growth characters measured were the number of leaves, trunk diameter, petiole length, rachis length, number of suckers, leaf length, length of the most extended leaflet, the width of the broadest leaflet, number of leaflets, and tree height.

3.1.Growth character of sago palm
The paired T-test results show a significant effect on the number of leaves of sago plants with differentages oftrunkformation (Table 2).The paired T-test results for each growth character measured showed that the average number of leaves and the width of the broadest leaflets differed significantly between groups of sago plants.There were no significant differences in other growth characteristics were observed between the three groups of sago palms studied.
The number of leaves on sago plants which form trunks more quickly (3 years) has more fresh green leaves, namely 19-24 leaves, compared to the number of leaves on sago plants which are slow to form trunks (4 years), namely 14-17 leaves.Whereas in sago plants that grow in optimum conditions, there are 24 leaves [7].In one study, sago plants had 9-12 leaves at the time before trunk formation and did not increase the number of leaves until trunks were formed [8].There are usually 10-20 fresh leaves at the time of trunk formation [5].Sago plants that form trunks after 3 years of transplanting have an average larger trunk diameter.In comparison, the smallest diameter is shown by the sago plant group that forms trunks at 3.5 years of transplanting.In line with research [9], larger trunk diameters lead to more forage production.Plants with larger diameters have longer roots and faster growth rates [10], [11], so water and nutrients will be greater-the more water and nutrients absorbed by plants, the more carbohydrates are produced through photosynthesis.

Relationship between morphological characteristics of sago plants
Trunk formation is the most crucial period in the life of sago plants.Sago plants store their main product (starch) in the trunk, so the trunk size is critical in calculating the potential for producing starch.The growth characteristics of other sago plants may be related to the size of the trunk diameter (figure 2).The tree height, length and width of leaflet, and rachis length have a significant direct effect on trunk's diameter.On the other hand, the number of leaves, number of leaflets, petiole length, and number of suckers were characters that had a direct effect but were not significant.This shows that the increase in trunk diameter can be influenced by the size of the tree height, rachis length, length and width of the leaflets.Meanwhile, the width of the leaflets which has a negative direct effect does not help increase the size of the trunk diameter.Ehara(2009) argues that leaf formation at the trunk formation stage is more constant every month than leaf length development [11].
Consistently, tree heightand rachis length showed a direct and a totally positive overall effect on trunk diameter.While the number of leaves is other growth characteristics that generally affect the formation of trunk diameter.The number of leaves is the most likely marker to be used as a selection marker [12].The increased number of leaves makes the leaf area larger as a place for photosynthesis to take place to Residual effect produce photosynthetic substrates for plant growth [5].Research ofYamamoto (2014) states that the rachis is the main part of the leaf that supports the leaflets and is responsible for positioning the leaflets to receive as much sunlight as possible [13].It is also very closely related to tree height which is important in assessing sago yields [5].
Constantly, rachis length and tree height showed a direct effect and a real positive total effect on trunk diameter.At the same time,another growth characteristic that shows a significant total effect on the formation of trunk diameter is the number of leaves.The number of leaves is the most potential character used as a selection character [12].An increase in the number of leaves occurs to produce a larger leaf area for photosynthesis to produce photosynthetic substrates for plant growth [5].As per researchofYamamoto (2014), the rachis is the central structure of a leaf that is responsible for placing the leaflets to capture as much light as possible [13].Tree height also has an important meaning in assessing sago crop yields [5].

Conclusion
Sago plants that formed trunks after 3 years of transplanting had more fresh leaves than sago plants that formed trunks 4 years after transplanting.The number of leaves, tree height and rachis length are three growth characteristics of sago plants which have a significant direct positive effect on the formation of trunk diameter, with cross coefficient values of 0.670, 0.520 and 0.549.

Figure 2 .
Figure 2. Diagram of the trajectory of growth and trunk diameter characters.(X1= Number of leaves; X2= Length of rachis; X3= Length of leaflets; X4= Width of leaflets; X5= Number of leaflets, X6= Tree height; X7= Petiole length; X8= Number of tillers; Y= Trunk diameter; tn = not real; **= real at 1% level; *= real at 5% level) competing in land cultivation.Sago can adapt well in marginal lands without the potential for other food crops.Sago can be a food reserve stored in the forest.

Table 1 .
Planting conditions in the sago cultivation experiment field for 4 years after transplanting.

Table 2 .
The growth character of sago plants at different ages of trunk formation after transplanting.