Natural or synthetic compounds that act as plant growth regulators (PGR) in a number of physiological and biochemical processes in plant is well known, which enables them regulating for rapid change in the phenotype of the plant within one season or two to reach the desirable results. Plant growth regulators are known to affect right from seed germination to senescence either by reducing the plant height (growth retardants) or by enhancing the growth (growth promoters) and ultimately yield. In recent years, the use of micronutrients is gaining more importance in improving the yield potential and also quality of the produce in several crops. Since, literature on the effect of organics, plant growth regulators and micronutrients on morphological, physiological, biochemical, quality parameters and yield attributes is very scanty in onion, literature on certain other related crops is also included in this chapter for better understanding of the subject.
Kabar (2008) observed the effect of kinetin and GA3 with respect to germination of spinach seed subjected to saline conditions. Kinetin increased germination rate significantly in comparison to GA3. Combination of both was also not effective like to kinetin. Katwale and Saraf (1990) applied NAA (20 ppm) and found that leaf area of chilli significantly increased due to NAA application. While Singh et al., (2000) different doses of NAA and observed that NAA (40 ppm) exhibited maximum leaf area of chilli plant. Nirmal et al., (1994) notified greater number of leaves and plant height when GA3 at 60 ppm was amendments as root dip or root dip + foliar spray at 30 days after transplanting of seedlings as compared to GA3 at 30 ppm and NAA at 15 or 25 ppm in onion.
Oboh, (2005) recorded highest height of okra plant at harvest time after applying 2 foliar sprays of tricontanol with the rate of 1.26 ppm and 2.8 ppm. Spray was done at rainy time in summer season. Likewise, Bray (1997) found that foliar spray of 4 to 34mg per liter increased leaf area, growth rate and leaf area index as compared to control treatment in crop of chilli.
Keithly and Yokoyama (2002) performed an experiment to study the impact of DCPTA (2-3, 4-dichlorophenoxy triethylamine) on growth and development of Radish seedlings. The results revealed that the spray of DCPTA with the dose rate of 30µm significantly increased the hypocotyl and root elongation rate, and also increased the dry weight of seedlings as compared to control. Harvest index and harvestable yield of the plants treated with DCPTA were 109 % and 38 % more respectively as compared to control. Narendra Singh et al., (1993) treated seed with GA and ethephon, and recorded that GA3 at 2 ppm exhibited highest plant height of potato in comparison to control.
Muhammad Wajid Khan, Rashad Mukhtar Balal, Muhammad Adnan Shahid and Mehwish Siddique
Department of Horticulture, University College of Agriculture, University of Sargodha