Wounding and Sugar Translocation

Abstract

Translocation of auxin occurs across cuts without difficulty. On the other hand, translocation of sugars, virus, caulocaline (1), and the flowering hormone (4) is only possible through intact vascular tissue. Wounds near vascular tissue have an effect upon growth of remote regions (2). Therefore, the relation between wounding through removal of leaves and bleeding, or stem elongation, as tests for sugar translocation was investigated (2).Tomato plants, when placed in darkness, lose their available carbohydrates within 30-50 hours. After this period all processes which require respiratory energy have dropped to a very low level. This level can be raised again 15-20 hours after applicationi of a 10 per cent. sucrose solution to some of the leaves (2).Effect of wounding on subsequent bleeding When the above-ground parts of a tomato plant are cut off, the stump bleeds profusely for a few days. When planits have been kept in darkness previous to the cutting, bleeding is mueh reduced. By applying sucrose to one or more leaves during the period in darkness, bleeding is increased afterwards, indicating the applied sucrose has been translocated to the root system (2). Four groups of 60-cm.-tall San Jose Canner tomatoes were brought into a dark-room kept at 250 C. One group of 20 plants was left as controls and the other three groups had two leaves per plant submerged in 10 per cent. sucrose. In one of these groups all other leaves were removed with a sharp razor; in another group the leaves were pinched off between thumbnail anld forefinger; and in the last group the plants were left intact. After 24 hours in darkness the tops of all plants were cut off, drip tubes were attached to the stumps, and the bleeding exudate collected. During the next four days the following amounts of exudate were collected (cc. per plant)

The Effect of Temperature Upon Translocation of Carbohydrates in the Tomato Plant

“…The activity of the root system is measured by the rate of exudation (bleeding) which requires respiratory energy (see e.g. VAN OVERBEEK,16 19) that cutting leaves off inhibited sugar trans-location in the stem somewhat more than when they were pinched off, and that this inhibitory effect decreased with time. The bleedometer used was described in an earlier paper (WENT 17).…”

“…Such wounds do not interfere with the basic rate. of bleeding, they only affect the sugar effect (WENT and CARTER, 19). This also proves that the increased rate of bleeding has its focus of activ-ity below the wound, and not in the upper parts of the stem.…”