Intensively farmed crops used to experience numerous environmental stresses.  Among these, shade and drought significantly influence the morpho-physiological and biochemical attributes of plants.  However, the interactive effect of shade and drought  on the growth and development of soybean under dense cropping systems has not been reported yet.  This study investigated the interactive effect of PEG-induced osmotic stress and shade on soybean seedlings.  The soybean cultivar viz., C-103 was subjected to PEG-induced osmotic stress from polyethylene glycol 6000 (PEG-6000) under shading and non-shading conditions.  PEG-induced osmotic stress significantly reduced the relative water contents, morphological parameters, carbohydrates and chlorophyll contents under both light environments.  A significant increase was observed in osmoprotectants, reactive oxygen species and antioxidant enzymes in soybean seedlings.  Henceforth, the findings revealed that, seedlings grown under non-shading conditions produced more malondialdehyde and hydrogen peroxide contents as compared to the shade-treated plants when subjected to PEG-induced osmotic stress.  Likewise, the shaded plants accumulated more sugars and proline than non-shaded ones under drought stress.  Moreover, it was found that non-shaded grown plants were more sensitive to PEG-induced osmotic stress than those exposed to shading conditions, which suggested that shade could boost the protective mechanisms against osmotic stress or at least would not exaggerate the adverse effects of PEG-induced osmotic stress in soybean seedlings.    

Under natural conditions, plants constantly encounter various biotic and abiotic factors, which can potentially restrict plant growth and development and even limit crop productivity.  Among various abiotic factors affecting plant photosynthesis, light serves as an important factor that drives carbon metabolism in plants and supports life on earth.  The two components of light (light quality and light intensity) greatly affect plant photosynthesis and other plant’s morphological, physiological and biochemical parameters.  The response of plants to different spectral radiations and intensities differs in various species and also depends on growing conditions.  To date, much research has been conducted regarding how different spectral radiations of varying intensity can affect plant growth and development.  This review is an effort to briefly summarize the available information on the effects of light components on various plant parameters such as stem and leaf morphology and anatomy, stomatal development, photosynthetic apparatus, pigment composition, reactive oxygen species (ROS) production, antioxidants, and hormone production.