Velemir Ninkovic | PubMed Health

PubMed2003

Volatile communication between barley plants affects biomass allocation.

Patterns of biomass allocation between different plant organs have often been used to explain the response of plants to variations in resource availability. This paper reports how aerial allelopathy (plant-plant communication) affects biomass allocation, that is the trade-off between root, stem and leaves, and also relative growth rate (RGR, increase in biomass per unit biomass per unit of time, mg g-1 d-1) and its components. Based on previous experiments, communication between two barley (Hordeum vulgare L.) cultivars (Alva and Kara) was used for the present study. Kara exposed to volatiles from Alva allocated significantly more biomass to roots compared with Kara exposed to volatiles from Kara or to clean air. There was no significant difference between plants of Kara exposed to volatiles from Kara and those exposed to clean air. Changes in total dry weight (TDW), RGR and unit leaf rate (ULR, increase in biomass per unit time and leaf area, kg m-2 d-1) were not significantly affected by plant-plant communication. However, there was a significant increase in specific leaf area (SLA, leaf area per leaf dry weight, m2 kg-1) in Kara when exposed to volatiles from Alva. The results show that aerial plant-plant communication does not affect total biomass production but does significantly affect biomass allocation in individual plants. There may be differences in the volatile profiles of Kara and Alva that induce increased biomass allocation to roots in the Kara plants exposed to volatiles from Alva.

Biomass↗

PubMed2003

Change in acceptability of barley plants to aphids after exposure to allelochemicals from couch-grass (Elytrigia repens).

The response of the bird cherry-oat aphid, Rhopalosiphum padi, to barley plants was investigated following exposure of the plants to root allelochemicals from the aggressive weed couch-grass, Elytrigia (Agropyron) repens. Plants were treated either with root exudates from living couch-grass plants or with previously identified couch-grass root compounds 15-hydroxyindole-3-acetic acid, DL-5-hydroxytryptophan, L-5-hydroxytryptophan hydrate, and 6-hydroxy-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (carboline)] either separately or in mixtures. In choice and no-choice settling tests, aphid acceptance of barley plants was significantly reduced following treatment with root exudates, and the carboline when tested alone or in combination with the other compounds. In contrast, the other compounds without the carboline were less active in reducing aphid acceptance. In a probing bioassay, individual substances were either neutral or stimulatory to aphids, indicating that the reduced settling was probably not due to direct effects on aphids, but rather due to effects on the plant. This was confirmed in olfactometer assays, in which aphids were repelled by odors from barley plants following treatment with a mixture containing all four chemicals.

Animals↗