ROOT-TO-SHOOT COMMUNICATION AND ITS SIGNAL CROSS TALK IN PLANTS: A PHYSIOLOGICAL AND AGRONOMIC PERSPECTIVE

The plant roots perceive and can respond to drying soil by transferring nHRS (non-hydraulic root-sourced signal) to aboveground plant parts deprived of any noticeable changes in water status of leaves. The nHRS has therefore been confirmed as a distinctive positive "quick-alert" reaction to soil drying in plants, triggering sequential physiological and molecular signalling pathways. Cross-talk infers to as occurrences where single or more constituents of a signal transduction pathway affect the others and might be accomplished via many pathways. We summarize the current progress regarding ABA-led root-to-shoot signals in relation to signalling cross-talk. Across signalling cross-talk, nitric oxide, reactive oxygen species, soil moisture threshold and others are broadly documented as conciliator of cross-talk throughout stress signalling. Here, we introduce a description of nHRS on stimulating the onset and process of signal cross-talk such as nitric oxide, reactive oxygen species, organic osmolytes, anti-oxidants, minerals and phytohormones. In particular, we have attempted to sketch out a flow chart of drought stress signal crosstalk with abscisic acid (ABA) and cytokinins (CTK/CK) as the center to describe eco-physiological link with multiple long-distance signalling pathways in plants. Eco-physiological framework and mutual interplay of complex signal elements in agronomic perspective during the operation of nHRS are also reviewed.