Physiological constraints to productivity in Indian mustard (B. juncea L. Czern Coss.)

摘要

Poor harvest index of rapeseed and mustard crop is one of the physiological constraint to productivity. The present paper focuses on the causes of poor partitioning of assimilates. Yield per se is complex character governed by many physiological attributes, viz: rate of photosynthesis, rate & magnitude of translocation from source to sink and the sink strength. Photosynthetic rate of leaves ofB. juncea, B. napus, and B. campestris was nearly equal, but higher than that of B. tournifortii. The photosynthetic rate of different species was in the decreasing order;, B. tournifortii, B. napus, B. campestris, B. juncea. Species B. tournifortii though has maximum photosynthetic rate is very poor seed yielder. Photosynthetic rate of the leaves as well as the flower buds was higher in B. napus, but it is poor yielder in most of Indian climatic conditions. Photosynthetic rate at 30 days after sowing stage was in the order: Upper leaves, lower leaves and middle leaves. At 60 days, it was lesser than at 30 DAS stage. Plucking lower half leaves at 40 to 70 days after sowing showed a significant increase in seed yield. When lower, middle, or upper leaf was fed with 14CO2, the maximum incorporation of radioactive 14C was from middle leaves. Comprehensive studies on B. juncea suggest that: compared to existing sink size, the source size is surplus. To divert translocation of assimilates from "vegetative sinks" (roots and lower leaves) to the siliquae; the magnitude of translocation needs to be improved through increase in sink strength.