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Methods and Materials
To determine the effect of leaf orientation on growth and reproduction, plants of both L. serriola serriola and L. serriola integrifolia were grown outdoors in pots. The pots were constructed of 15 cm diameter PVC pipe and were 75 cm deep. The depth of the pots was sufficient to allow the plants to root naturally. Two treatments were used. Plants in the control group were allowed to grow and orient their leaves naturally. Plants in the experimental group were manipulated so that the cauline leaves were prevented from orienting vertically, east-west; emerging cauline leaves were restrained with fine wires attached to an adjacent rod. Once the leaves were fully expanded the restraints were removed since leaves would not reorient. In general the leaves of the experimental plants were forced to orient in all directions with angles of 0 - 45° from horizontal. The wires did not damage the leaves, covered an extremely small surface area of the leaves, and had no effect on leaf shape or area.
The plants were watered periodically during the course of the growing season. Each plant received the same amount of water. Water loss was monitored by weighing entire pots. To avoid damage to the plants and pots due to excessive handling, only a subset of plants (N = 7) in each of the treatments was used for these measurements.
All plants were harvested at the same time. Flower production, above-ground dry weight, and below-ground dry weight were determined. During the weeks preceding the harvest, matured seeds were harvested from flowers to determine average number of viable seeds per flower and average seed weight. Above-ground biomass included stems, leaves, and flower stems. Below-ground biomass included all root material recovered by washing roots over a 0.5 cm mesh screen. Plant material was oven dried at 60° C for 48 hours.
To determine the effect of leaf orientation on growth and reproduction, plants of both L. serriola serriola and L. serriola integrifolia were grown outdoors in pots. The pots were constructed of 15 cm diameter PVC pipe and were 75 cm deep. The depth of the pots was sufficient to allow the plants to root naturally. Two treatments were used. Plants in the control group were allowed to grow and orient their leaves naturally. Plants in the experimental group were manipulated so that the cauline leaves were prevented from orienting vertically, east-west; emerging cauline leaves were restrained with fine wires attached to an adjacent rod. Once the leaves were fully expanded the restraints were removed since leaves would not reorient. In general the leaves of the experimental plants were forced to orient in all directions with angles of 0 - 45° from horizontal. The wires did not damage the leaves, covered an extremely small surface area of the leaves, and had no effect on leaf shape or area.
The plants were watered periodically during the course of the growing season. Each plant received the same amount of water. Water loss was monitored by weighing entire pots. To avoid damage to the plants and pots due to excessive handling, only a subset of plants (N = 7) in each of the treatments was used for these measurements.
All plants were harvested at the same time. Flower production, above-ground dry weight, and below-ground dry weight were determined. During the weeks preceding the harvest, matured seeds were harvested from flowers to determine average number of viable seeds per flower and average seed weight. Above-ground biomass included stems, leaves, and flower stems. Below-ground biomass included all root material recovered by washing roots over a 0.5 cm mesh screen. Plant material was oven dried at 60° C for 48 hours.
