Studies on Water Relations in Mustard( Brass/Ca Juncea L.)

Abstract

Effect of soil moisture on ~rowth, yield and water use of two mustard (Brassica Juncea L.) cultivars (Sambal and Daulat) was studied. The two moisture levels were irrigation at every 10 days intervals and rainfed control. Total dry matter (TDM), leaf area index (LAI) and leaf area Iniuration (LAD) were siirnif.icantly higher in the irrigated plant.~ than that of the rainfed plants. The increase of TDM production wns !dow at the early vegetative phases but increased rapidly with I.hf' Advancement of the growth period. StnrLin~ from 1-1. lowe"r vnl11", LAI and LAD reached a peak and then declined gradually. Among the growth attributes, relative growth rate (RGR), leaf area ratio (LAR), relative leaf growth rate (RLGR) and leaf weight ratio declined throughout with the increasing time and plant weight. Specific leaf area (SLA) showed no clear pattern but crop growth rate ( CGR) increased slightly with fluctuations . Net assimilation rate (NARI increased at the later stages of growl.h . Sign if i.can t ly higher CGR, LAR, SLA and LWR we re found j n t.l1P irrigated plants of both the cultivars than that of the rainfed plants.Simple correlation coefficients indicated that in the irrigated plants, seed yield was positively correlated with the preflowering LAI and CGR and the post-flowering NAR. In the rainfed plants,seed yield was positively correlated with LAI and CGR at the post-flowering stage and negatively correlated with the postflowering NAR and the pre-flowering LAR. Percentage of dry matter (DM) accumulation for stem and petiole was lower at the early stages, at the middle stages it increased to a peak and .then ~radually decreased with time.Percentage of DM accumulation in the leaves was found highest atthe i~itial stage and ~radully decreased with time and ultimately it became zero.Dry matter partitionin~ for pods gradually increased with plant a~e. No clear effect of soil moisture on partitioning of dry matter was found. At the flower.in~ stage, the irrigated plants had significantlyhi~her relative leaf water content (RLWC)than the rainfed plants at 8 A.M. in both the cul.tivars. At the mid-pod fillin-' ( sta~e, the irri~ated plants had significantly higher RLWC at 8 A.M. and 4 P.M. than the rainfed plants of Sambal. The highest RLWC was observed at 8 A.M., but at the midday it decreased and later part of the dny it jncreased gradually.----