MSc

Studies on “Endogenous and exogenous regulation of growth and development in Dendrobium var. Sonia 17 and Sonia 28” were conducted in the Department of Pomology and Floriculture, College of Horticulture, Vellanikkara during the period from June 1999 to November 2000. The main objectives of the trial were to study the factors responsible for changes in growth and development of Dendrobium var. Sonia 17 and Sonia 28 with a view to solve field problems and to enhance production.
The influence of endogenous factors indicated that the variety Sonia 17 was superior to Sonia 28 with respect to the number of shoots, number of leaves, total leaf area and number of florests, while the internodal length was more in Sonia 28.
The stomatal frequency was higher in Sonia 28 whereas the stomatal size was more in Sonia 17. Increased dry weight was recorded in the third stage (keiki formation) in Sonia 17. Leaf area index, specific leaf weight and relative growth rate did not differ significantly. The chlorophyll (a, b and total) content did not show any significant differences between Sonia 17 and 28. The total phenolic content was significantly higher in Sonia 28 during the fourth stage (senescence of spike). The Concentration and uptake of all the nutrients were at par during all the stages of growth, between Sonia 17 and Sonia 28.
Studies on exogenous factors revealed that Greencare (13:27:27) at 0.2 per cent level improved the in number of leaves in Sonia 28. The stomatal density and size were significantly influenced by the treatments in both the varieties. Leaf area index, relative growth rate and total dry matter production did not vary significantly, either at the emergence of shoot or at the emergence of spike. However, specific leaf weight varied significantly during Stage I (emergence of the shoot) in both the varieties.
The concentration of nitrogen was significantly influenced by the treatments at the shoot emergence stage, in Sonia 17. In Sonia 28, significant differences were not observed among the treatments during both the stages of growth. Though the concentration of phosphorus was not influenced by the treatments that of potassium differed significantly among the treatments during both the stages in Sonia 17 and Sonia 28.
The highest uptake of nitrogen was recorded in the treatment involving 1:10 groundnut oilcake during shoot emergence stage, in both the varieties. During spike emergence, the highest uptake was caused by 500 mg 1-1 BA in Sonia 17 and 1:10 groundnut oilcake in Sonia 28. With respect to phosphorus, in Sonia 17, the highest value during both the stages was recorded in plants treated with 0.1 per cent Greencare. In Sonia 28 the highest uptake of P at both the stages was with the treatment 1:10 groundnut oilcake. In Sonia 17 the highest K uptake was with 1:20 groundnut oilcake during the emergence of shoot while during the emergence of spike the highest uptake was with 0.1 per cent Greencare. In Sonia 28, during the emergence of shoot, the highest uptake of K was with a combination of 0.1 per cent Greencare + 1:10 groundnut oilcake whereas during the emergence of spike the highest value was recorded in plants receiving 1:10 groundnut oilcake alone.
The chlorophyll and total phenolic content differed significantly in the two varieties during both the stages of growth. In Sonia 17, Greencare significantly improved the chlorophyll content at both the stages. In Sonia 28, maximum chlorophyll content during the emergence of shoot, was recorded in plants receiving 0.1 per cent Greencare, whereas, during the emergence of spike 1:20 groundnut oilcake recorded the highest value. In sonia 17, the total phenolic content at the emergence of shoot was produced by 1:10 groundnut oil cake + 0.1 per cent greencare + 250 mg I-1 BA and during spike emergence, by a combination of 0.1 per cent Greencare + 250 mg I-1 BA. In Sonia 28, at the emergence of shoot, the highest phenolic content was recorded by 500 mg I-1 BA and during the emergence of spike, by 1:10 groundnut oil cake.
Studies conducted using 32 P revealed that translocation of 32 P occurred from the backbulb to the younger shoots.