Low irradiances affect abscisic acid, indole-3-acidic acid, and cytokinin levels of wheat (Triticum aestivum L.) tissues

Wheat (Triticum aestivum L.) plants were grown under four irradiance levels : 1,400, 400, 200, and 100 mu mol.m(-2).s(-1). Leaves and roots were sample d before, during, and after the boot stage, and levels of abscisic acid (AB A), indole-3-acetic acid (IAA), zeatin, zeatin riboside, dihydrozeatin, dih ydrozeatin riboside, isopentenyl adenine, and isopentenyl adenosine were qu antified using noncompetitive indirect ELISA systems. Levels of IAA in leav es and roots of plants exposed to 100 mu mol.m(-2).s(-1) of irradiance were 0.7 and 2.9 mu mol.kg(-1) dry mass (DM), respectively. These lexis were 0. 2 and 1.0 mu mol.kg(-1) DM, respectively, when plants were exposed to 1,400 mu mol.m(-2).s(-1). Levels of ABA in leaves and roots of plants exposed 10 0 mu mol.m(-2.)s(-1) were 0.65 and 0.55 mu mol.kg(-1) DM, respectively. The y were 0.24 mu mol.kg(-1) DM (both leaves and roots) when plants were expos ed to 1,400 mu mol.m(-2).s(-1). Levels of isopentenyl adenosine in leaves ( 24.3 nmol.kg(-1) DM) and soots (29.9 nmol.kg(-1) DM) were not affected by d ifferences in the irradiance regime. Similar values were obtained in a seco nd experiment. Other cytokinins could not be detected (<10 nmol.kg(-1) DM) in either experiment with the sample sizes used (150-600 mg DM for roots an d shoots, respectively).