Fig 1.
Potential of Ag+-viability medium (consisting of 0.5 mM AgNO3 and 300 mM KNO3) to stain wheat pollen brown in presence of high-intensity light (~600 μmol PFD m-2s-1).
(A) Variation in color of medium (300 mM KNO3) with 0 and 0.5 mM Ag+ incubated with wheat pollen in presence of high-intensity visible light (l) and dark (d) for 5 min; (B) Light microscopic image of wheat pollen showing brown stain; (C) Absorption spectra of sonicated media with wheat pollen incubated with 0 and 0.5 mM Ag+ in the presence of high-intensity visible light.
Fig 2.
Ag+-viability medium imparted brown staining of wheat pollen is due to AgNPs.
(A) Transmission electron micrograph show distinct AgNPs in the sonicated pollen after incubation with Ag+-viability medium in presence of light; (B) Energy dispersive X-ray (EDX) pattern showing Ag peaks; (C) Selected area electron diffraction (SAED) pattern; (D) PXRD pattern of AgNPs formed by the wheat pollen incubated with Ag+ viability medium in presence of light. Bragg reflections confirmed that these AgNPs are biphasic composed of Ag0 '()' and Ag2O '()*'.
Fig 3.
Inability of (A) wheat pollen that turned non-viable on storage for 4 h; and (B) heat-killed wheat pollen to stain brown on incubation with Ag+-pollen viability medium in presence of light, indicating that live protoplasm is essential for rapid photoreduction of Ag+ for uniform brown staining. Please note mixture of viable and non-viable pollen in (A).