WheatBP

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Development Home Germination Early growth and tillering Stem elongation Wheat apex development Flowering and fertilisation Pollen release Grain growth 1 to 4 days Grain growth 4 to 10 days Cell layers inside a grain Grain filling 11 to 16 days Grain filling 17 to 21 days Grain filling 21 to 30 days Development of the embryo Dry down 30 to 40 days How we grew the plants Further details
Photography and microscopy
DAYS = days after flowering

How the plants were grown

Here are some photographs of our plants as they grew in the Controlled Environment Rooms.

For the IGF project we needed to harvest grains at very specific stages in the grain's development. Knowing how many days old the plants or grains were would not be good enough. We needed to know exactly which tissues were present at any sample time and so, by inference, which genes might or might not be active. The only way to know this was to simultaneously sample grains for DNA extraction and for microscopic analysis.

Plants in Controlled Environments

Our chosen variety was Mercia, a bread-making wheat with a hard endosperm. Mercia is a winter wheat: sown in the field in the autumn and overwintered as a rosette plant with several tillers. It has a cold requirement; in other words the plants must receive a winter chill in order to grow and flower naturally the following spring and summer. We needed to use uniform plants from a reproducible source. For these reasons field grown plants would not be acceptable. They would not be uniform and we could only achieve one harvest in a calendar year, so all our plants were grown in artificial, but reproducible, conditions in large Controlled Environment Rooms. This meant we could sow and harvest continuously through the year.

Firstly we had to satisfy the chilling requirement and then we had to provide the correct artificial environment, (temperature, humidity, day length and light intensity) for the plants to grow steadily through to flowering and then on through the grain filling stages until harvest ripe. We had several attempts before we got it right! The eventual success was in no small way due to the skill and experience of our support staff, Bob Hughes, Richard Parkinson and Godfrey Hardbard to whom we are most grateful.

The sophisticated 'walk-in' Controlled Environment Rooms allowed us independent control of day and night temperature, day and night humidity, and both the intensity, duration and quality of the light.

Details of the schedule are in the table below: the abbreviations are:

Temp. - temperature: degrees Celsius

RH - relative humidity: %

Ppd - photoperiod (daylength): hours

PAR - photosynthetically-active radiation: µmols m^-2 s^-1

Light was supplied by 56 metal halide lamps (250W), designed to give a spectrum similar to 'natural daylight'. The lamps were lit daily, in sequence, to provide the required PAR. The PAR was a minimum of 250 µmols m^-2 s^-1 as the crop was established and a maximum of 850 µmols m^-2 s^-1 as the crop started to ripen.

Additionally, independently switched tungsten lights were provided for 30 minutes longer than the metal halide lamps, at each end of the photoperiod, to simulate a dawn and dusk, when the far red part of the natural light spectrum is higher.

If you compare these images with those of the plants grown outside in the field (see section: Early Growth and Tillering) and you will spot some differences in plant form as they experience an artificial winter and spring compared to the natural seasons. The differences disappear once the plants come to full canopy and flowering.

Table of Growth Room Parameters

 

Growth stage	Days from sowing	Days in CE room		Temp	RH	Ppd	PAR
Seeds germinate in module trays in the cold room.	0 to 42	-	Day	4	ambient	12	40
			Night	4	ambient	-	-
One week in a cool greenhouse.	43 to 50	-	Ambient green house conditions.
2 - 3 leaves	51 to 63	0 to 12	Day	8	75	14	280
			Night	5	75	-	-
3 - 5 leaves	64 to 77	13 to 27	Day	9	75	14	280
			Night	6	75	-	-
Tillering (raised bench)	78 to 89	28 to 39	Day	11	75	15	280
			Night	7	75	-	-
Stem extension (low bench)	90 to 101	40 to 51	Day	13	75	15	560
			Night	9	75
Flag leaf emerges	102 to 113	52 to 63	Day	15	70	16	560
			Night	11	75	-	-
Flowering	114 to 128	64 to 78	Day	16	70	17	850
			Night	12	75	-	-
Grain growth	129 to 143	79 to 93	Day	17	70	17	850
			Night	13	75
Grain filling	144 to 158	94 to 108	Day	19	70	16	850
			Night	15	75	-	-
Harvest ripe	159 to 190	109 to 140	Day	20	70	16	560
			Night	16	75	-	-

For information on this web site, please contact: Mark.Winfield