Alternanthera tenella Colla - Departamento de Agronomia - UEM

ABSTRACT
CANOSSA, Rosecler Salete, M.S., State University of Maringá, February, 2007.
Requirements for germination and emergence of sanguinaria
(Alternanthera tenella Colla) and alternatives for chemical control. Adviser:
Dr. Rubem Silvério de Oliveira Junior. Co-advisers: Dr. Alessandro de Lucca e
Braccini and Dr. Jamil Constantin.
Alternanthera tenella Colla is a very frequent weed in a variety of important
crops. A very few studies on germination and on factors affecting its emergence
are available. The objectives of this research were to promote understanding of
aspects related to germination, emergence and chemical control of A. tenella.
Three experiments were run. For the first one, in greenhouse conditions, seeds
were placed in PVC columns filled with soil under seven different depths and
two soil covers (with or without straw). Seedling emergence was recorded daily
up to 28 days after sowing and the total % emergence for each treatment was
calculated, as well as the speed of emergence-index (SEI). The second
experiment was conducted in laboratory. Seeds were placed in plastic boxes
“gerbox” and kept in B.O.D. type germination chamber, under constant regimes
of temperature of 20, 25, 30 and 35 ± 1 o C in the dark and at 25 ± 1 o C under
continuous light. Counting of normal seedlings was recorded daily and total %
emergence and speed of germination-index (SGI) were calculated after 34
days. The third experiment was composed by two greenhouse trials: in the first
one, alternatives of chemical control were applied in pre-emergence; in the
second one, alternatives for post-emergence (application at three pair of leaves)
control were evaluated. Evidences were found showing that seedling
emergence of A. tenella seeds is limited to seeds placed up to 4-cm depth in
soil. Seeds placed at 10-cm depth do not emerge. Straw covering of soil
inhibited seedling emergence of seeds placed at soil surface. In the second
experiment, increasing temperatures promoted increased seed germination up
to a maximum at 28.16 o C, decreasing thereafter. All herbicides applied preemergence
were considered as efficient to control A. tenella, propitiating at
least a 98% control at 28 days after application (DAA). In relation to postxiii