Through thorns to the leaves

Plants need a plant so that no one ate it. By “nickname” we usually mean mammals, but, it turns out, thorns can also interfere with herbivore insects. Of course, they do not dig in the mouth of the caterpillar, but they significantly complicate the food process.

However, the researchers until recently did not pay much attention to the thorns, they were more interested in other means of protection: toxic substances secreted by plants, as well as glandular and non -ferrous hairs. Several years ago, specialists of the University of Pennsylvania, led by Professor Andrew G. Stephenson) studied the mechanisms of plant stability to herbivorous insects. They worked with the caterpillars of the Manduca Sexta tobacco hazelnik and the Caroline Slanum Caroline Carolinse : ordinary plants and inbred, obtained through 10-15 generations of self -pollination.

Closely related crossing affects many signs; In inbred plants, it, including, reduced the number of spines. And it turned out that the caterpillars of the Brazhnik are more damaged by such plants [1]. Moreover, on the growing stems of the nightshade living under the yoke of the caterpillars, more spines are formed than on clean plants, and on young leaves - more hairs.

Caterpillars that feed on the plant constantly crawl from sheet to sheet. Scientists suggested that the thorns physically interfere with the caterpillars to move and thus protect the plant from eating. This hypothesis was already checked in the Swiss Higher Technical School of Zurich, where two participants in the previous study moved: Rupesh R. Kariyat and Mark Mescher [2].

In the experiments, they used the third -age caterpillars hatching in the laboratory of the same size. In each experience, individuals from one masonry participated. As the first test, the caterpillars were offered a high -speed race along the stem of the Caroline nightshade.

Scientists picked up 40 ordinary and 26 inbred plants of the same height and stage of development, but with a different number of thorns on the stems, cut off all the leaves except the highest, and put the caterpillar on the ground at the base of the stem. Brazhniks rushed up to the source of food. As scientists expected, the first to finish the caterpillars that crawled through inbred plants with rare thorns. To get to the sheet, it took them almost half the time than the brawls who stormed ordinary nightshade.

However, inbred plants can have other properties affecting the speed of movement of caterpillars. To exclude this factor, the researchers cut off part of the thorns in ordinary and inbred plants. As a result, they received several pairs of nights with a similar amount and the location of the thorns. Inbredens were pruning in order for all plants involved in the experiment to have physical damage - during the cut, toxic for pests of the substance can be released. And it turned out that, moving along the stems with the same number of thorns, the caterpillars reached the goal in a similar time. Therefore, the thorns really interfere with pests to crawl.

But do they interfere with feeding? To answer this question, scientists compared the time necessary for the caterpillars to completely destroy the leaves on three types of nightshade: S. Carolinense , incredibly prickly spilled brown S. atropurpureum and almost bald nightshain of the Ethiopian S. aethiopicum (Fig. 1). Brazhniks with the same appetite burst leaves of all three types.

The dry weight of S. Atropurpureum on one plant is 0.144 g, on California - 0.093 g and on Ethiopian - 0.022 g and the more prickly plant, the longer its caterpillar is gnawed (Fig. 2). Cutting the thorns from the stems significantly accelerated the process of eating leaves on S. atropurpureum and S. Carolinense , but not on S. aethiopicum - it is almost smooth.

The researchers were convinced that the thorns serve as an effective anti -human fence, and the thicker they are, the more reliable the protection (Fig. 3). The dark brown cliff is so that the caterpillars often fell from him, and scientists had to plant them back to complete the experiment. If this is not done, the plant retains the leaves at least twice as long.

Prillic plants are not just more difficult to damage or completely swallow. Caterpillars who eat less are developing more slowly, which affects their viability. Uncooded pests more often get a predator. Moreover, the growth rate can affect the processes of molting and pupation, as well as the success of subsequent mating. So the thorns are an underestimated device.

Natalia Reznik

1. Kariyat RR, Balogh CM, Moraski RP, De Moraes CM, Mescher MC, STEPHENSON AG Constitutive and Herbivore-induced Structural Defenses are compromised by inbreeding in SOLANUM CAROLINENSE (Solanaceae) // Am. J. Bot. 2013. 100. R. 1014–1021. DOI: 10.3732/Ajb.1200612

2. Kariyat RR, Hardison SB, De Moraes CM, Mescher MC PLANT Spines Deter Herbivory by Restricting Caterpillar Movement // Biol. Lett. 2017. 13: 20170176. DOI: 10.1098/RSBL 2017.0176