The growth of the garlic of Lumbu Hijau variety in three different microclimatic conditions

More than 90% of the need for garlic consumption in Indonesia is supplied from imports. One of the efforts to minimize the dependence on the import of garlic is through microclimate manipulation sub-tropical conditions in the growth chamber. This study aims to examine the growth of the early vegetative phase and bulb of garlic in three different microclimatic conditions. The experimental design used was a Randomized Block Design with four replications. The treatments consisted of three microclimatic conditions, i.e. (1) Smart Growth Chamber (SGC) in a tray with solar spectrum of LED irradiation conditions with a constant intensity of 10.000 lux; light/dark period of 14/10 hours controlled temperature of 22-25°C and humidity of 60–70%; (2) open field in trays, and uncontrolled microclimate (control 1); and (3) open field in mulched plots; and uncontrolled microclimate (control 2). The parameters observed were the plant height, growth rate, chlorophyll content, bulb size and qualitative character. Data analysis used was the Analysis of Variance (ANOVA) followed by LSD significant difference test using the PKBT-Stat 3.1 version. The results of the study showed the initial success in manipulating microclimatic conditions through planting in SGC. The plant height, growth rate, chlorophyll content and bulb size in SGC were higher than control 1 and control 2.


Introduction
Garlic is a vegetable crop commodity that is used in Indonesia as a cooking spice and medicinal ingredient.Garlic production and consumption in Indonesia is unbalanced, in 2021 national garlic consumption will reach 506.42 thousand tons while national garlic production is only 45.09 thousand tons [1].Based on these data, there is a problem with the garlic commodity, because more than 90% of 1230 (2023) 012188 IOP Publishing doi:10.1088/1755-1315/1230/1/012188 2 fulfilling the demand for garlic relies on imports [2].So, efforts are needed so that consumption of garlic does not depend on imports.
Efforts that can be made to reduce dependence on imported garlic are by improving local garlic products.Local varieties that are widely planted in Indonesia include Lumbu Hijau [3][4][5].Short-term improvement of local varieties can be done by engineering the growing environment, while long-term improvements can be done through genetic engineering/plant breeding programs [6].Improvements through genetic engineering have obstacles, namely because garlic does not produce flowers [7], so the breeders cannot do anything to improve the genetics of plants.Environmental engineering is more likely to be carried out, including by using the Smart Growth Chamber (SGC).
The Smart Growth Chamber (SGC) is a controlled growing room with adjustable microclimatic conditions because the SGC has a series of sensors that can control microclimate parameters such as temperature, humidity, and light.In addition, SGC can monitor and control in real time.Plants require controlled climatic conditions to grow optimally, so the purpose of this study was to determine whether environmental engineering with SGC could improve the phenotypic appearance of Lumbu Hijau garlic.

Materials and Methods
The research was conducted at the IP2TP Margahayu Experimental Garden, Lembang West Java, Ministry of Agriculture of the Republic of Indonesia from October to November 2022.The experimental design used was a complete randomized block design with 3 treatments and 4 replications.The treatments were 3 microclimate conditions namely.(1) Smart Growth Chamber (SGC) in a tray with solar spectrum LED irradiation conditions with a constant intensity of 10,000 lux; exposure within 14 hours, and within 10 hours in the dark; controlled temperature of 22-25°C and controlled humidity of 60-70%;  These results indicate that the scope for growing in SGC was more suitable for plant height growth, due to sufficient light received and more stable temperature and humidity without any disturbance from the surrounding environment.The process of photosynthesis will takes place optimally if the light and temperature conditions are available according to the needs of the plant [8,9].The Controlled environmental conditions enabled plant to grow and develop better [10][11][12].

Figure 3. Growth rate at three microclimate conditions
Garlic plant growth is strongly influenced by genetic factors and the environment in which it grows [13].The speed of plant growth is faster if the growing environmental conditions, like light and temperature are better controlled.Temperature and light affect plant metabolic processes such as photosynthesis, respiration, transpiration as well as the metabolic processes of synthesis and organic transport.In the process of plant growth, photosynthetic activity, respiration and other metabolic activities require enzymes whose activity varies with changes in temperature [14,15].Plant growth requires a suitable temperature range.Plants can grow faster and produce the most accumulated organic matter if they are in the optimal temperature range for growth [16,17].

Chlorophyll Content
Statistically, the chlorophyll content of plants grown in SGC was higher than in the plants of control 1 and control 2 (figure 4).The increase in the chlorophyll content of garlic plants in SGC was 31.80% against control 1 and 29.50% against control 2.
Controlled temperature and increased the chlorophyll content in the leaves.The content of chlorophyll in the leaf's changes with changes in temperature to a certain extent.Temperature affects the activity of enzymes that play a role in protein synthesis, low temperatures will accelerate the degradation of chlorophyll in plant leaves [18].

Bulb Size
Bulb height at 7 weeks after planting was statistically significantly different (figure 5).SGC produced higher bulb height than control 1 and control 2. The increase in bulb height to control 1 and control 2 was 33.33% and 50%, respectively. .As with bulb height, bulb diameter was also significantly affected by the treatments (figure 6).The diameter of garlic bulbs planted in SGC was higher than control 1 and control 2 by 58.33% against control 1 and 59.66% against control 2.
Garlic requires 14-16 hours of light for optimal bulb formation [13,19,20].This causes the size of the bulbs in SGC to be larger because the duration of the light set for 14 hours, while the length of the day in the field is less than 14 hours.Garlic bulb formation is mainly influenced by genetic and environmental factors, especially day length.A larger bulb diameter of garlic was obtained with the 14/10 hour light/dark period than with the 12/12 and 10/14 hour period [21].

Qualitative Character
The qualitative character in this case is to compare the qualitative character of the treated garlic with the description of garlic of the Lumbu Hijau variety.The qualitative character of garlic in SGC and control 2 was the same as the description of Lumbu Hijau varieties both from leaf shape, leaf blade, leaf color and anthocyanin color intensity on pseudostems.There is a difference in control 1 in the character of leaf color, where the leaf color of control 1 is green type Green Group 143A, while the description of green leaf color varieties is type Green Group 137B RHS.This is because it is influenced by differences in chlorophyll content in the leaves of each treatment.Disease pests also caused the color of garlic leaves in control 1 to be lighter.Moisture is the main cause of plant diseases.High humidity causes the emergence of diseases caused by fungi, plant leaf necrosis, plant leaves become weak and thin, otherwise if the humidity is too high it will inhibit plant growth [22].
(2) open field in trays, and uncontrolled microclimate (control 1); and (3) open field in mulched plots; and uncontrolled microclimate (control 2).Parameters observed were quantitative characters including plant height, growth rate, chlorophyll content and bulb size.Observations were also made on qualitative characters.Observational data were analyzed of Variance (ANOVA) followed by LSD significant difference test using PKBT-Stat software version 3.1.

Figure 1 . 3 .
Figure 1.Microclimatic conditions: (a) Smart Growth Chamber, (b) control 1, (c) control 23.Results and Discussion3.1.Plant HeightPlant height is affected significantly by the treatments.The plant height of SGC at one month after planting (44.2 cm) was higher than planting in trays in open field (28.1 cm) and planting in mulched plots in open field (29.8 cm).These results indicate that the scope for growing in SGC was more suitable for plant height growth, due to sufficient light received and more stable temperature and humidity without any disturbance from the surrounding environment.The process of photosynthesis will takes place optimally if the light and temperature conditions are available according to the needs of the plant[8,9].The Controlled environmental conditions enabled plant to grow and develop better[10][11][12].

3 Figure 2 .
Figure 2. Garlic plant height at three microclimatic conditions 3.2.Growth Rate Figure 3 shows that the growth of the garlic plants aged 3 to 30 days after planting in SGC was faster than control 1 and control 2. The average growth speed of garlic in SGC (1.9 cm/day) was faster than the plants grown planting in trays in the open field (1.3 cm/day) and in mulched plots in open field (1.4 cm/day).

Figure 4 .
Figure 4. Chlorophyll index on three microclimatic conditions

Table 1 .
Comparison of the qualitative characters of garlic in three microclimatic conditions with the description of garlic of the Lumbu Hijau variety Plant height, growth rate, chlorophyll content and bulb size of the green Lumbu varieties grown in SGC were significantly higher than those grown in open land.Cultivation of Lumbu Hijau garlic in SGC did not change the phenotypic appearance of the qualitative characters.SGC is suggested to boost garlic productivity in the tropics.