Tuesday, October 20, 2015

Improving Germination Speed of Zoysia Seed - Seed Priming

When I first started research and development on zoysia the germination of the seed was a very tricky process.......low germination was common, especially with fresh seed.

Then a few scientists, including myself, began work to see if this could be improved.  Some work on related species showed that quite a few tropical grasses had tightly oppressed covers [glumes] around the seed [ caropysis], and that removal or damage that allowed moisture to penetrate improved germination.  Zoysia also exhibited this trait, and germination could be improved by piercing the glumes.  It worked in the lab, but a practical larger scale option was needed.

A process devised by a Chinese scientist showed that seed treatment with potassium hydroxide was effective in dramatically improving germination as it seemed to both soften the hard glumes and allow water to penetrate as well as overcome dormancy in the embryo.

This then became a commercial treatment, and is used today.

Light is also required and best germination in the laboratory is achieved with light [ and remember that seed is sown very close to the surface for that reason] -   no light and germination is much lower in the lab.

The other technology that relies on the inherent physiology and biochemistry of the germinating damp seed is a technique known as seed priming.  

Short term wetting of the seed starts the physiological and biochemical processes leading to germination........but if you then dry the seed along the way.....that process stops.  When you re-wet the seed, the process continues,  but restarts from the point you redried the seed, so the second time germination and seedling emergence process is much shorter.

For zoysia these processes are now being looked at  as a means to reduce the time from sowing to emergence, which can be normally up to 14 or more days, especially in cooler conditions.

You can prime the purchased seed ie the seed ready to germinate as having been treated to soften the glumes - overnight is currently recommended - in water.  Then the next day the damp seed is washed and spread out and dried in the light or even sunshine which provides a light stimulation.

This technique is now being recommended in the US for improving the time between sowing and seedling emergence.

While exact times and water temperatures are not stated in technology leaflets, the recommendation is a dark period soak eg overnight followed by draining and then drying out in light / warm sunshine.  I would be cautious about the temperature of tropical sunny days, but the principle seems clearcut - with this recommendation by one of the major seed producers of zoysia seed in the US.

Once the seed is dry, it is then sown normally, with an expected shorter time to germinate in the field. This potentially is a great boost in agronomic management options including irrigation, and allows seedlings to be established in the field much quicker.

We have not evaluated this here in Australia but the scientific principles are sound and broadly work for a range of other species, although timing of the soak period does vary among different species.

If you try the technique we would be interested in hearing of the experience.

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