The role of ducking stems in plant anti-herbivore defense and its exploitation by herbivorous insects

Abstract

Goldenrod stems whose apices nod are shown to have architectural resistance against some herbivorous insects that attack terminal buds. In Japan and other regions, many other plant species including herbs, climbers, shrubs and trees have similar ducking stems during young developing stages. Several herbivorous insects that attack young shoots cause stems to droop, resulting in an appearance similar to ducking stems. Thus, I postulated that ducking stems of many plants may also function to deter some phytophagous insects in addition to preventing photoinhibition, and that insects, especially stem-borers that induce stem drooping, may achieve fitness gains by reducing predation, parasitism and attacks on infested stems by other herbivores. Alternative mechanisms causing stem-ducking and experimental tests of the hypotheses and future directions are discussed.

Girdling behavior of the longhorn beetle modulates the host plant to enhance larval performance

“…Natural history observations on behavioral modulations suggest various functions of behavioral modulations. As most behavioral modulations damage the vascular bundles [ 9 ], the subsequent effects have been predicted to be the inhibition of defense signaling [ 20 ] and accumulation of nutrients [ 22 , 23 ]. Moreover, the modified morphology of modulated plants is suspected to be utilized for evasion of natural enemies [ 20 ].…”

“…As most behavioral modulations damage the vascular bundles [ 9 ], the subsequent effects have been predicted to be the inhibition of defense signaling [ 20 ] and accumulation of nutrients [ 22 , 23 ]. Moreover, the modified morphology of modulated plants is suspected to be utilized for evasion of natural enemies [ 20 ]. However, other than disarming defense mediated by canal-borne exudates, experimental testing on functional consequences of behavioral modulations at the molecular level has been seldom compared to copious hypotheses.…”

“…Different herbivores feeding on the same plant interact with each other via plant traits including systemic responses [ 19 ] and altered plant appearance [ 10 ]. As behavioral modulation changes plant morphology [ 20 ] and palatability [ 21 ], it may alter the responses of other herbivores sharing the same host plant. Indeed, canal cutting promotes the feeding of other herbivores that originally do not feed on plants with secretory canals [ 21 ].…”

Girdling behavior of the longhorn beetle modulates the host plant to enhance larval performance

“…Natural history observations on behavioral modulations suggest various functions of behavioral modulations. As most behavioral modulations damage the vascular bundles [9], the subsequent effects have been predicted to be the inhibition of defense signaling [20] and accumulation of nutrients [22,23].…”

Defense with benefits? Ducking plants outperformed erect plants in the goldenrod Solidago gigantea in the absence of herbivory

“…Furthermore, the different pattern of relative frequencies of ducking and erect plants between Solidago altissima and S. gigantea suggest that such ecological constraints may differ in character or intensity among different species of goldenrods. Observations of similar patterns of nodding stems in other plant species suggest that the phenomenon of resistance‐by‐ducking may be more widespread than just a curiosity possessed by a few species of goldenrods (Yamazaki, ). If nodding in other plant genera and families is associated with resistance to herbivory, it will be interesting to learn whether and how some species have overcome the costs of ducking.…”