**4.4 Heavy metal toxicity**

Excessive uptake of heavy metals leads to chlorosis and reduction of production of seed through alteration of physiological, morphological, biochemical, molecular activities of plant. It negatively impacts on seed germination, accumulation and remobilization of seed reserves and photosynthetic activity resulting in loss of seed yield. Heavy metal toxicity reduces the yield also through synthesis of ROS, increased rate of lipid peroxidation and disrupting redox equilibrium. Lower uptake of nutrients such as N reduces quality *viz.*, protein of seed produce. Cd, Pb. Cr, Ni, Zn, Cu, As etc. reduce starch, protein, oil and minerals contents of seed. Decrease of oleic acid and linoleic acid and increase of palmitic acid, linolenic acid and stearic acid are found under heavy metal toxicity specially, under high Cd and Hg.

### **4.5 Other abiotic stresses**

Use of excessive chemicals and nutrients lead to deterioration soil and water health, loss of beneficial micro-organisms activity and drastically hampers seed production and quality of the crop. On a contrary, nutrient deficiency can lead to poor yield and quality of the crop as photosynthesis and various metabolic activities are seriously affected under scarcity of nutrients. High wind causes erosion, loss of nutrients, lodging and evapotranspiration water loss which affect the plant growth and various physiological functioning inside the plant including photosynthesis. Further, high wind velocity causes loss of pollen which in turn, impacts on fertilization and seed production. Shattering loss of seeds is another major issue associated with high wind velocity. Light impacts on photosynthesis. Shading or low light hampers photosynthesis and translocation of photo-assimilates to reproductive parts and thereby, affects seed production and quality. Excessive light, on the other hand, disrupts photosynthetic apparatus including chlorophyll and hampers the photosynthetic activity of plant. Further, it creates water scarcity or high temperature, which in turn hampers various functioning of plant system and thereby, affects seed yield quantitatively and qualitatively.
