Effect of nutrient- N, P and K starvation on root growth of soybean [Glycine max (L.) Merrill] seedlings

摘要

An attempt was made to study the root growth of soybean [Glycine max (L.) Merrill] seedlings grown under water culture experiment in relation to starvation of nutrients- N, P and K. Observations were recorded for different root parameters as well as on shoot growth using appropriate measuring software and equipments. Results revealed that biomass of stem, petiole and leaf were drastically reduced in nutrient starvation viz. -N, -P, -K and -NPK compared to +NPK treatment. The decrease of total plant dry weight was 27, 25, 24 and 33% in 4-week old seedlings, and 47, 46, 45 and 50% in 5-week old seedlings in -N, -P, -K and -NPK, respectively. Root length was the most important parameter to be studied under nutrient starvation. The maximum total root length was recorded in +NPK and the lowest in -N treatment under both 4- and 5-week old seedlings. The reduction in root length was 87% in -NPK and -N in 4- and 5- week old seedlings compared to +NPK. The relative decrease of root length due to -P and -K was lesser than the reduction due to -N or -NPK. There was also a distinct decrease in the root surface area, dry weight, root/ shoot ratio, root volume and average diameter due to N, P & K starvation. Root length distribution in different root diameter classes revealed that the total root length was greater in finer roots. Root length decreased gradually with the increase in diameter. Length was more in the 0.1-0.2 mm diameter class; about 50% of the total root length belonged to 0.1-0.2 mm root diameter class in 4- and 5-week old seedlings. Total root length under 0.1-0.2, 0.2-0.3, 0.3-0.4 and 0.4-0.5 mm diameter classes was 80-90%. Our findings also revealed that relative reduction in root growth due to P-starvation would be lesser in comparison to Nand K- starvation.