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PPDC Seed Botany lab

Plant Pest Diagnostics Center - Seed Botany Laboratory

Research Programs - Seed Botany

CDFA Seed Botanists

Seed Taxonomy


Identification of Brassica seeds

Scientist:
Jim Effenberger

Brassica

Using ImageJ software develop photo analysis measuring criteria for the identification of Brassica seeds. The seeds in general of Brassica are broadly oblong, spherical, slightly flattened laterally, or triangular in outline. In many of the species the uneven length of the underlying palisade cells produces on the surface a network of lines or ridges of irregular pattern called reticulation. The relative size of the interspaces created by the reticulation pattern is often characteristic of the species. The type of reticulation and the relative size of interspaces may be considered the most important features in making the identification. Until now because of the minute size of these structures it has not been practical to designate measurements that could be considered characteristic of a species.


Musk thistle
(Carduus nutans)

Scientist:
Don Joley

 

Current projects

  • Impact of Rhinocyllus conicus on musk thistle at Mt. Shasta, California.

Yellow starthistle
(Centaurea solstitialis)

Scientist:
Don Joley

 

Current projects

  • Impact of Eustenopus villosus on yellow starthistle seed production.
  • Impact of Urophora sirunaseva on yellow starthistle seed production.
  • Long-term changes in plant cover of field plots infested with yellow starthistle.
  • Long-term impact of a guild of seedhead insects on yellow starthistle seed production and plant density.

Seed Viability and Germination


Seed moisture determination

Scientist:
Dr. Riad Baalbaki

seed moisture

Seed moisture content is an important aspect of seed quality.  Determining a seed lot’s moisture content is essential for avoiding imbibitional injury and standardizing vigor tests. Seed moisture content is also a critical variable in many seed physiology and seedling development investigations. In transactions involving trade and movement of seeds within and across borders, one requirement is to accurately state a lot’s moisture content. The California State Seed Laboratory has contributed to developing moisture testing protocols for more than 70 species, as part of seed testing rules. This ongoing project aims at developing quick and standard moisture determination methods for many more species.


Smoke stimulated germination

Scientist:
Dr. Riad Baalbaki

smoke stimulated germination

Seed germination of many wild species, with seed banks in serotinous cones and fruits or in soil, is triggered by fire-related events. Fire-promoted germination can be either due to heat-shock or chemical constituents in smoke. One compound in smoke that promotes germination has recently been identified as butenolide (furanone), a by-product of cellulose combustion. Several studies have shown that butenolide can also improve seed germination and enhance seedling vigor of commercially bred varieties. Evaluating the possible uses of butenolide in commercial seed testing and understanding its mechanism of action will provide benefits for agriculture and land restoration, and can overcome many of the seed dormancy problems encountered when evaluating native and wild species.


Coleoptile-first leaf patterns of development

Scientist:
Dr. Riad Baalbaki

Coleoptile-first leaf patterns of development

The coleoptile, only present in species of Poaceae, develops in the seed and encloses the shoot with its leaf primordia. Upon germination, it pushes upwards to the soil surface, guiding the shoot and protecting it on the way. Growth of the leaves causes the coleoptile to split and the primary leaf to emerge from the coleoptile. Patterns of coleoptile and primary leaf development are used in determining whether a seedling is classified as normal or abnormal. Possible causes of abnormal coleoptile-first leaf development include seed infections, heat damage, chemotoxicity, mechanical damage, low vigor, and unfavorable germination test conditions. Preliminary studies in our lab have indicated that normal development of those two structures is often asynchronous, commonly leading to erroneous classification of normal seedlings as abnormal. This project aims at studying the prevalence and degree of variation in coleoptile-primary leaf development, as well as germination test conditions that might contribute to this variation.


Methods in Seed Science


Uniform Blowing Procedure

Scientist:
Deborah Meyer

General Blower

Poa secunda seed units

The seed quality assessment method known as the Uniform Blowing Procedure (UBP) employs a calibrated air steam within a General-type Seed Blower (top photo) to separate pure seed from inert matter. Previous studies indicate test results based on the UBP were less variable within and among laboratories than those based on manual separation methods. Test efficiency was also greatly improved with the UBP. In the United States, the UBP is the standard purity testing procedure recognized by the Association of Official Seed Analysts (AOSA); but its used is limited to seven grass species. With increasing demands for faster sample turn-around time, ongoing projects seek to expand the use of this procedure to more grass species as well as other types of seed.