Standardization of growth promoters for mangosteen (Garcinia mangostana L.) seedlings

Abstract

Mangosteen (Garcinia mangostana L.) is a promising fruit crop for Kerala due to high price and consumer demand. Slow growth of the seedlings and prolonged pre bearing period are the major factors limiting large scale cultivation of mangosteen. In this context, the present study entitled ‟Standardization of growth promoters for mangosteen (Garcinia mangostana L.) seedlings” was carried out in the Department of Fruit Science, College of Horticulture, Vellanikkara during 2018 to 2019. The main objective of the study was to identify the ideal combination of plant growth promoters for enhancing the growth of mangosteen seedlings. The experiment was laid out in CRD with seventeen treatments replicated thrice. In each replication ten plants were maintained per treatment. Six month old seedlings planted in eight inch pots containing a medium composed of soil + sand + vermicompost in 2:1:1 ratio. Foliar application of NPK mixture (3:1:1) at 0.5 % and 1 % and growth promoters such as GA3 (300 ppm), thiamine (100 ppm), ascorbic acid (100 ppm) were given at monthly intervals during the entire study period (April 2018 to April 2019). Observations on growth characters, root characters, physiological parameters were recorded periodically at different stages of the study. Growth characters such as plant height, plant spread, number of leaves, length and breadth of leaves, total leaf area and internodal length, number of branches were recorded at quarterly intervals upto twelve months after planting. Significant difference was observed among the treatments with respect to plant height and taller seedlings (33.32 cm) with the longest internode (9.44 cm) were observed in T6 (NPK (3:1:1) 0. 5 % + GA3 300 ppm + ascorbic acid 100 ppm. Better plant spread (34.27 cm) was observed in seedlings sprayed with NPK (3:1:1) 0. 5 % (T1). Application of plant growth promoters had no effect on number of leaves produced by mangosteen seedlings. Control plants recorded the highest number of leaves (15.11), which was statistically on par with NPK (3:1:1) 0. 5 % (T1). Leaf length was found to be

superior in T1 (NPK (3:1:1) 0. 5 %) at twelve months after planting. However, breadth and total leaf area and Leaf Area Index (LAI) were not influenced by foliar application of nutrients and growth promoters. In general, there was a reduction in all leaf parameters such as number of leaves, leaf length, breadth, total leaf area and LAI in treatments involving GA3. Application of growth promoters could not induce branching in mangosteen seedlings during the period of study. Total number of roots (85.67) was the highest in T1 (NPK (3:1:1) 0. 5 %). Length of the longest root did not show any significant difference among the treatments. However, root spread differed significantly. NPK (3:1:1) 0. 5 % (T1) and NPK (3:1:1) 0. 5 % + thiamine 100 ppm (T3) were the two superior treatments with respect to root spread. Treatments involving GA3 alone and in combination with other growth promoters had an inhibitory effect on root growth and development. Shoot: root ratio was found to be higher (4.64) in T6 (NPK (3:1:1) 0. 5 % + GA3 300 ppm + ascorbic acid 100 ppm) which was on par with control plants. Root hairs were absent in the plants even after twelve months of planting. Highest fresh weight (24.48 g/plant) and dry weight (9.83 g/plant) were noticed in T1 (NPK (3:1:1) 0. 5 %). Plants were analysed for major nutrients (N, P and K) twelve months after planting. Nitrogen, phosphorus and potassium content in the seedlings ranged from 1.4 % - 2.17 %, 0.03 % - 0.10 % and 1.01 % - 1.65 % respectively. Highest nitrogen uptake (190.10 mg/plant) was found in seedlings applied with NPK (3:1:1) 0. 5 % (T1). Higher uptake of phosphorus (5.01 mg/plant) and potassium (120.23 mg/plant) was recorded in T4 (NPK (3:1:1) 0. 5 % + ascorbic acid 100 ppm). The study clearly indicated that foliar application of NPK (3:1:1) 0.5 % (T1) at monthly intervals can be recommended for enhancing the growth of mangosteen seedlings, as superior growth parameters were observed in this treatment. No significant increase in seedling growth was noticed with the foliar spray of NPK 1%.