Agriculture Reference
In-Depth Information
The excised embryo test should be conducted and interpreted with caution. A high degree of skill and
time are required and care must be taken to avoid injuring the embryo during its removal. It does not reveal
embryo damage other than that present in the root-shoot axis that might prevent normal germination of the
intact seed.
Figure 5.11. Excised embryo test. It is used when dormany is present in the seed coat.
Prewashing and Soaking
Chemical inhibitors are often located in the fruit or seed coat tissues of seeds. If water soluble, they can
be removed by soaking or prewashing the seeds in running tap water for a specii ed period (3 to 48 hr) of
time, a process known as “leaching.” Examples that require prewashing include
Beta
and
Tetragonia
spp
.
and
Citrullus lanatus
var.
citroides
. After washing, seeds are germinated using recommended procedures.
Prewashing can be performed in a metal pan having walls 2.5-in high with a drain spout 0.75-in from
the top and a false bottom soldered to the walls 1.0-in from the bottom. The false bottom should have a
0.094-in hole beneath each seed basket measuring 1.5 x 1.5-in in cross section and 2-in high made of 20 x
6 mesh copper gauze. As water enters the compartment between the bottom and false bottom, it squirts up
through each hole, thereby agitating and prewashing the seeds (Justice, 1972).
removal of outer Structures
For some species, germination is promoted by removing outer structures such as the lemma and palea of
certain grasses that may contain germination inhibitors.
CAuSES of LoSS of GErMInAbILITy
From the time of planting through harvest, storage, conditioning, and marketing, the seed passes through
many channels, each designed to enhance and improve its quality and performance. If handled inappropri-
ately, each stage can reduce rather than enhance its germination capability. Thus, most quality assurance
programs constantly monitor seed lots to ensure that only high quality seeds are produced and marketed.
