Sonic-induced cellular vibrations unzip intertwined anther cone trichomes to trigger floral self-pollination and boost tomato fruit size

Abstract

Summary Artificial tomato pollination methods rely on cellular vibrations from air displacement, electric vibration wands and trellis tapping, which have potential to spread pathogens. Bioacoustic frequencies emitted from buzzing bees to ultrasonication can vibrate plant cells without physical contact. The effects of frequency-dependent sonication on the poricidal anther cone sheath, self-pollination, seed set, and fruit size remain unclear. We engineered devices to investigate the frequency-dependent power-law behaviour of floral living cells from greenhouse-grown tomato varieties - contrasting contact-induced oscillations from a vibrating wand and mechanical shaker arm with precision non-contact sonication emitted by a subwoofer speaker. The velocity and acceleration of vibrating flowers and impact on poricidal anther cone sheath cellular structures, self-pollination, and fruit development were assessed. Sonic frequencies ranging from 50 to 10 000 Hz increased pollination, fruit size, weight, and seed set in Sweetelle, Endeavour, Paulanca and Managua commercial varieties. Scanning electron microscopy revealed sonication separated the intertwined trichomes and unzipped their meshed network that locks the lobes of the anther cone sheath together thereby releasing pollen grains. Near ultra-sonic frequencies boosted fruit size, whereas seed set remained constant thereby challenging the floral cell power-law rheological characteristics under different frequency scales. Tomato flowers displayed a low power-law cell behaviour to frequency-dependent sonication enabling its effectiveness as a precision non-contact technology to boost pollination and tomato fruit size without a substrate-borne component.