environment and genotype of the mother plant, it is advisable
to obtain seed weight estimates for the specific materials to be
used. If admixtures of seeds from different genotypes are sown
in a single pot or tray, a bulked mix can be first prepared by
mixing the desired number of seeds of each genotype based on
seed weight estimates. Thereafter, seed aliquots can be stored
in Eppendorf tubes for the same weight of seed mix.
17. To reduce the effect of soil variability on plant phenotypes, a
standard commercial soil or soil/vermiculite/sand mix can be
used. When aiming to study soil effects, soil from the natural
site of the field experiment, or from other natural environments, could be used. In this case, soil must be carefully
collected to reduce the large soil heterogeneity across single
natural sites [66].
18. It is advisable to place some pots with soil but without seeds
intermingled with the rest of pots. These blank pots allow the
estimation of cross-contamination after seed sowing. Rain
always produces a small splash that may eventually end up in
cross-contamination, which can be increased by wind. There
are different ways to reduce the extent of cross-contamination:
(1) pots should not be filled with soil to the brim, but 2–3 cm
below it (Fig. 1c, d); (2) pots can also be separated a few cm
from each other if the overall size of the experiment allows that;
and (3) a wire mesh on top of the blocks protecting the pots/
trays also minimizes the impact of rain drops on the pots
(Fig. 1b, g).
19. When sowing, seeds must be homogeneously distributed
across the pot or tray surface by carefully shaking the Eppendorf tube containing the seeds. When large amounts of seeds
are sown on a single tray/pot, the cap of the Eppendorf tubes
can be first punctured with a needle of the appropriate diameter. A uniform seed distribution will then be ensured by using
the tube as a salt shaker. Nevertheless, heavy rain episodes after
seed sowing can eventually determine the final position of
seedlings within the pot/tray.
20. To detect potential temperature/precipitation differences
among blocks, it is advisable to place one climate datalogger
per block inside a pot, or next to the experiment pots (Fig. 1b,
j). Depending on the aim of the experiment, dataloggers can
record data on an hourly basis, every few hours, or on a daily
basis. When multiple loggers are not available, one datalogger
in the middle of the experiment might provide the information
on temperature and precipitation in the field site. In addition,
weather information can be collected from a climate station at
the site, or from nearby automatic meteorological stations
from national public meteorological agencies.
Analyses of Natural Variation
103
to obtain seed weight estimates for the specific materials to be
used. If admixtures of seeds from different genotypes are sown
in a single pot or tray, a bulked mix can be first prepared by
mixing the desired number of seeds of each genotype based on
seed weight estimates. Thereafter, seed aliquots can be stored
in Eppendorf tubes for the same weight of seed mix.
17. To reduce the effect of soil variability on plant phenotypes, a
standard commercial soil or soil/vermiculite/sand mix can be
used. When aiming to study soil effects, soil from the natural
site of the field experiment, or from other natural environments, could be used. In this case, soil must be carefully
collected to reduce the large soil heterogeneity across single
natural sites [66].
18. It is advisable to place some pots with soil but without seeds
intermingled with the rest of pots. These blank pots allow the
estimation of cross-contamination after seed sowing. Rain
always produces a small splash that may eventually end up in
cross-contamination, which can be increased by wind. There
are different ways to reduce the extent of cross-contamination:
(1) pots should not be filled with soil to the brim, but 2–3 cm
below it (Fig. 1c, d); (2) pots can also be separated a few cm
from each other if the overall size of the experiment allows that;
and (3) a wire mesh on top of the blocks protecting the pots/
trays also minimizes the impact of rain drops on the pots
(Fig. 1b, g).
19. When sowing, seeds must be homogeneously distributed
across the pot or tray surface by carefully shaking the Eppendorf tube containing the seeds. When large amounts of seeds
are sown on a single tray/pot, the cap of the Eppendorf tubes
can be first punctured with a needle of the appropriate diameter. A uniform seed distribution will then be ensured by using
the tube as a salt shaker. Nevertheless, heavy rain episodes after
seed sowing can eventually determine the final position of
seedlings within the pot/tray.
20. To detect potential temperature/precipitation differences
among blocks, it is advisable to place one climate datalogger
per block inside a pot, or next to the experiment pots (Fig. 1b,
j). Depending on the aim of the experiment, dataloggers can
record data on an hourly basis, every few hours, or on a daily
basis. When multiple loggers are not available, one datalogger
in the middle of the experiment might provide the information
on temperature and precipitation in the field site. In addition,
weather information can be collected from a climate station at
the site, or from nearby automatic meteorological stations
from national public meteorological agencies.
Analyses of Natural Variation
103