Animal saliva has stronger effects on plant growth than salivary components

Abstract

Mutualism between plants and animals demonstrates that grazing has positive impacts on plant growth. Animal saliva plays an important role in plant–herbivore interactions, and various salivary components work for the beneficial relationship. This study was performed to compare responses of Leymus chinensis (Trin.) Tzvelev. (Poaceae) to sheep saliva and two salivary components. One randomized block designed experiment was conducted in 2007 with six treatments: control, clipping with water, with saliva, with epidermal growth factor (EGF), with thiamine and with mixture of EGF and thiamine. There were significant differences between treatments on biomass, buds and tillers of L. chinensis. Compared with control plants, there was no compensatory response in clipped plants due to the limited number of available meristems in late‐growing season. Plants in clipping with saliva had more biomass and buds than those in clipping with water or salivary components. Clipping with salivary components had no stimulatory effects on plant growth, relative to clipping with water. The results showed that herbivore saliva had greater impacts than salivary components, and there was no additive effect between salivary components on plant growth. This study demonstrated the complexity in saliva components, which offer saliva with the capacity to play an important role in plant–herbivore interactions.

Is animal saliva a prominent factor in pasture regrowth?

“…All such effects impact the acquisition and allocation of plant resources including water, nutrients and photo assimilates and as such, observations regarding changes in growth rates are not uncommon. Nevertheless, evidence has suggested that application of saliva to the leaf surface elicits growth promotion in addition to these effects (Table 1) (Reardon et al 1972(Reardon et al , 1974Dyer and Bokhari 1976;Reardon and Merrill 1978;Dyer 1980;Howe et al 1982;Kato et al 1993;Rooke 2003;Loeser et al 2004;Teng et al 2010;Gullap et al 2011;Liu et al 2012;Li et al 2014). Deposition of saliva onto grasses during grazing occurs as animals lick forage to direct biomass into their mouths, or the mouth come into contact with grass; both of which leads to the transfer of chemicals to the un-grazed plant tissue (McNaughton 1985;Liu et al 2012;Huang et al 2014).…”

“…Previous studies have also attempted to use 'synthetic' saliva as a substitute, and was a concept initially proposed by Jameson (1964). However, results of studies that used a synthetic version have often suggested that the growth response of plants do not elicit the same response compared to the use of real saliva (Reardon et al 1974;McNaughton 1985;Lamy et al 2010;Huang et al 2014;Li et al 2014). Animal saliva used in contrast, has been found to have a larger impact on plant growth than any synthetic substrate used, further contributing to the complexity of understanding the impact that individual substrates may have (McNaughton 1985;Li et al 2014).…”

“…Furthermore, saliva may have growth promoting effects beyond that of the concomitant effects elicited by the removal of leaf area. Studies have reported that the addition of saliva can stimulate growth in plants (Young and Schneyer 1981;Dyer et al 1982;McNaughton 1985), and others have also examined the use of chemical alternatives to saliva, which have resulted in similar growth promoting responses (Reardon et al 1974;Lamy et al 2010;Huang et al 2014;Li et al 2014). However, little to no studies have explicitly determined what constituents in livestock saliva will stimulate pasture growth.…”

“…Saliva glands are known rich sources of growth promoting chemicals for plants, such as epidermal, nerve, and transforming growth factors (Cohen 1962;Frazier et al 1974). Steroid hormones have also been found alongside growth factors in saliva and has been reported to also have physiological impacts on plant growth (Dyer and Bokhari 1976;Detling et al 1981, Teng et al 2010Li et al 2014). Growth factors have been reported to intervene directly in cellular metabolism through promotion of differential transcription of genes (Murdoch et al 1982).…”

Untargeted Metabolome Analyses Revealed Potential Metabolic Mechanisms of Leymus chinensis in Response to Simulated Animal Feeding

“…In addition to the important role of JA, the saliva of herbivores is also very important in the process of animal feeding. For example, Li et al compared the effects of water, sheep saliva, epidermal growth factor (EGF), thiamine, and the mixture of EGF and thiamine on the growth of clipped L. chinensis and found that the biomass and buds increased after sheep saliva treatment rather than water treatment, although the animal saliva components had no cumulative effect on plant growth [ 17 ]. Moreover, animal saliva can also affect the level of hormones in plants [ 18 ].…”