Plant can perceive its environment

Plant can perceive its environment changes and transduce the stimulus signal to internal gene systems, where the related genes are activated and transcripted with related enzymes synthesized to catalyze and control biochemical processes for related regulations and adjustments (Mulligan et al., 1997; Yang et al., 1997; Romeis et al., 2000; Smith and Gallon, 2001). Such knowledge has been used to breed plant varieties resistantto adverse environment, such as drought. In research on plant resistance to drought and other adverse environment, scientists usually focus on finding resistant varieties, which are suitable to be grown in adverse environmental conditions. With this knowledge, human has done all this in passive positions to fight against the coming adverse environment. In recent years, scientists have changed their positions to active and tried to induce expected consequences by imposing artificial stimuli to plants. These artificial stimuli include modest drought by restricted irrigation or cultivation practices, partial root drying, hypocotyl exposure, low humidity and rhizosphere salinity. These practicesdonotnecessarily cause real stresses andjustinduce stimulus signals. In our previous studies, a healthy crop characterized by high leafturgor potential, high photosynthetic capacity and high seed yield was induced by exposing hypocotyl of peanut (Xu et al., 2009a) or mesocotyl of sorghum (Xu et al., 2009b). Usually, elongation of the hypocotyl of a peanut plant is easily stopped by sun light irradiation through the soil surface crack when the peanut seed is germinating. Consequently the cotyledons remain beneath the soil surface, causing early flowering and early seeds setting. The pods early set on the branches from the cotyledon node compete for carbohydrates with the young plant and the early seeds will rot in soil before harvest. The carbohydrates demand by the early pods would negatively affect the plant growth and, if rotted, contaminate the other pods with aflatoxin (Shen and An, 1988). The problem was solved by inducing peanut hypocotyl elongation by placing more soil over that seed and the elongated hypocotyl was exposed to light by removing the soil over the germinating seed. As early reported and proved by the peanut crop experiment, the hypocotyl is sensitive to light, especially blue light as a component of the strong light. Therefore, it must be interesting if blue light can be a stimulus to induce health consequences of a crop through the so-called blue light response. Plant blue light response was reported as early as 1881 by Darwin after he discovered what is now known as the blue light-induced phototropic response (Darwin, 1881).