Boron Fertilization Enhances the Induced Defense of Silver Birch

Abstract

Boron (B) deficiency is a common micronutrient deficiency that has been reported to affect the phenolic metabolism of plants. Thus, it may play a role in defense against herbivorous animals. However, the role of B in a plant's resistance to herbivores has not received any particular attention from researchers. In this study, we tested the effects of B nutrition 1) on the biochemical and mechanical defenses of birches and the growth of seedlings, and 2) the resistance of seedlings to larvae of the autumnal moth, Epirrita autumnata. Boron fertilization improved the resistance of birch, which was shown as reduced pupal weight of the herbivore. However, B fertilized trees suffered from heavier defoliation than unfertilized ones due to compensation feeding of larvae. The growth of the seedlings was diminished, and several biochemical changes occurred in leaves of herbivore seedlings, and B also played a role in these changes. Polyphenoloxidases (PPOs) and peroxidases (PODs) and their substrates, chlorogenic acids, were induced by herbivory in B fertilized seedlings but not in unfertilized seedlings. The lower pupal weights and increased consumption of the herbivores were probably linked to the plants' phenoloxidase-mediated production of reactive quinones, which decrease the nutritive value. Herbivory upon new stems led to an increase in the number of resin glands that provide defense against mammalian herbivores. Herbivory also had a substantially negative effect on B concentration in leaves of B fertilized seedlings. We postulate that B nutrition of trees may play a significant role in the induced defense of birches.

BORON FERTILIZATION IN PLANTATIONS OF Eucalyptus urophylla S.T. Blake in TABASCO

“…These concentrations are higher than those reported for the genus (Freitas et al, 2009) and three to five times higher than those found in other forest species fertilized with B such as T. grandis (Zhou et al, 2012) and Pinus radiata D. Don (Hawkins, Xue, Bown, & Clinton, 2010). It has been observed that fertilizing Betula pendula Roth seedlings with B can improve the concentration of this nutrient in the foliage by up to 50 % (Ruuhola, Leppanen, Julkunen-Tiitto, Rantala, & Letho, 2011). Figure 5 shows the response of the nutrients to the application of different B doses in E. urophylla.…”

Biochemical and growth acclimation of birch to night temperatures: genotypic similarities and differences

“…1999) and is associated with a defence against UV and herbivory (Tegelberg et al. 2002; Ruuhola et al. 2011), but on the other hand, it has also been found to increase during leaf development (Laitinen et al.…”

Ellagitannins: defences of Betula nana against Epirrita autumnata folivory?

“…PPOs convert phenols to electrophilic quinones capable of alkylating electron-rich moieties of amino acids and proteins, reducing their assimilation in the digestive tract of herbivores (Felton et al, 1989). PPOs have been shown to be induced in other boreal birch species by herbivory (Ruuhola & Yang, 2006;Ruuhola et al, 2008Ruuhola et al, , 2011Anttila et al, 2010) and to affect negatively the growth of E. autumnata (Ruuhola et al, 2008(Ruuhola et al, , 2011. There was no difference in the phenology between controls or defoliated plants (data not shown) that could explain the increased protein concentration in defoliated plants.…”

“…Similarly, in silver birch, B. pendula, the levels of myricetin-, quercetinand kaempferol-3-rhamnosides were increased by herbivory (Ruuhola et al, 2011); rhamnosides may have a defensive role in boreal birches.…”

“…Furthermore, the concentration of CTs has been reported to decline in herbivory-treated B. pendula (Huttunen et al, 2008;Ruuhola et al, 2011) and their precursors in Betula pubescens ssp. czerepanovii (Anttila et al, 2010).…”