Involvement of auxin in growth and stress response of cucumber

Cucumber(Cucumis sativus L.)is an important vegetable,popular worldwide for its crispy texture and special flavor.Plant hormones such as auxin stand out for its dominating function in morpho-and organogenic processes,formation of organs as well as regulation of tropic responses.These developmental processes are entirely,or partially dependent on auxin biosynthesis,transport,and signal transduction.In cucumber,auxin not only fine-tunes its morphogenesis but also its response to environmental stress.The role of auxin in regulating different organs(root,hypocotyl,shoot,leaf,tendril,flower,and fruit)development in cucumber is reviewed in the present paper.Moreover,the role of auxin in cucumber response to biotic stresses(powdery mildew,downy mildew,and nematode infections)and abiotic stresses(heat,iron,waterlogging,cold,salinity,drought,and heavy metal stresses)is discussed.Finally,we point out the blind spots and future research thoughts to extend our understanding of this myriad molecule in cucumber growth and stress biology.