Effects of spraying plants with suspensions of inert dusts*

Abstract

SUMMARYIn an examination of possible harmful effects to plants caused by spraying leaves with inert dust suspensions it was shown that Stockalite (kaolin), talc, silica or Tiona W.D. (titanium oxide), suspended in water and sprayed on excised leaves of three species, significantly (P≯ 0·05) increased water loss and penetration of gaseous ammonia; these increases were not caused by soluble chemicals in the sprays, but depended on intimate contact of the dust particles with the epidermis. With a given dust, epidermal permeability increased with increasing concentration and with decreasing size of particles. The increased permeability persisted for at least 4 weeks and was unaltered by partial removal of deposits; deposits on bean leaves caused more visible damage in dry than in humid air. Water losses from sprayed adaxial and abaxial leaf surfaces were similar, but more was lost when deposits dried on turgid leaves than when they dried on flaccid ones.Spraying potted Coleus plants with a Stockalite suspension increased transpiration and, in one test, decreased the fresh weight of the Coleus shoots.

Plants and Atmospheric Aerosols

“…Dust application to leaves of kidney beans and cucumbers reduced stomatal conductance in the light (Hirano et al 1995), but increased conductance in the dark if stomata were still open during dust application. Similarly, application of chemically inert aerosol such as silica gel to Populus tremula leaves (Fl€ uckiger et al 1977) and of kaolin, silica, talc, copper oxychloride, quartz, and other inert suspensions to Phaseolus multiflorus, Coleus blumei, Zebrina pendula, and Solanum tuberosum obstructed stomatal closure and increased water loss and drought injury, with stronger effects at increasing concentration and decreasing aerosol size (Eveling 1969(Eveling , 1972.…”

Hygroscopic particles on leaves: nutrients or desiccants?

“…Chemically inert silica gel particles on Populus tremula leaves prevented the complete closure of stomata and led to excessive water loss resulting in drought injury (Flu¨ckiger et al 1979). Similarly, transpiration increased after the application of kaolin, silica, talc, copper oxychloride, quartz and other inert particles or suspensions, and this was interpreted as a physical effect, where stronger effects were caused by increasing concentrations and decreasing particle size (Eveling 1969(Eveling , 1972. Transpiration was increased by the application of ''Bordeaux mixture,'' a suspension of copper hydroxide and more complex insoluble copper particles used as a fungicide (Frank andKru¨ger 1894, Duggar andCooley 1914), with the greatest effect at night (Krausche and Gilbert 1937).…”

Responses of herbaceous plants to urban air pollution: Effects on growth, phenology and leaf surface characteristics

“…There are a limited number of studies tha s, usually in the form of increased water loss, of inert dusts (Eveling, 1969;Farmer, 1993).…”