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 Ámols 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

-

-