Leaf area and biomass at five-leaf stage to start of stem elongation – DC15 to DC31

Within the manual Protocols for experimental plot sampling, handling and processing of cereals in field experiments by G.J. Rebetzke (Greg.Rebetzke@csiro.au), A. van Herwaarden, B. Biddulph, C. Moeller, R. Richards, A. Rattey and K. Chenu.

In some cases, estimates of DC stage, early leaf area and biomass may be required simultaneously. Where a precise estimate of plant establishment in uniform plots has been attained (see page 9), the following method may be used on a per plant basis.

Method

1. As each wheat line reaches 5-6 leaves, two options can be used to sample the plants:
   (a) Walk down one side of the plot and in 2-3 places randomly grab 3-4 plants near ground level and gently pull from the ground. You should end up with 10 representative plants. Do not sample from edge rows and avoid sampling all plants from a single row. Sampling individual plants can sometimes risk overestimation of biomass and leaf area (and thereby LAI).
   (b) A more accurate measure of leaf area and biomass is to sample on a unit area basis by simply placing a quadrat or ruler to identify and harvest multiple adjacent rows. The larger the area sampled the better although it is sometimes easier and more precise to sample two separate parts of the same plot particularly if the plot is variable for growth. Sampling in the early morning or late in the day is easier on you and the crop samples.
   In both cases, make sure the sampling is done in a zone that will not be used later on for other sampling.
   To remove some plants, grab them near ground level and gently pull from the ground.
2. If you have plastic bags, put each sample into a bag with an identifying tag and go onto the next plot. Collect all bags into a larger bag (e.g. clean fertiliser bag) and place into a cold room or refrigerator until ready for measurement.
3. When ready to take measurements, open each bag and if plants are muddy, gently wash.
4. Record the date of sampling for each wheat line/cultivar. Count the number of plants and the total number of shoots (tillers + main stem) including main stems. Separate three random plants and record numbers of leaves, leaf lengths and leaf widths. Cut plants at ground level (where tissue changes from green to white; Fig. 12) and discard white below-ground stem and roots. Remove and separate fully expanded and unopened leaves (i.e. leaf with the ligule visible) from young, still growing leaves of all 10 plants and pass through a leaf area machine to get total leaf area. Put leaves and stems into a labelled paper bag and place into a dehydrator @ 60-70^∘C. If assessing C¹²/C¹³ discrimination then place the separated leaves into a separate, labelled paper bag.

 

Figure 12. Plant samples (a) cleaned in preparation for removal of roots and crown (arrow) and leaf area meter (b) which is here a Li-3100 Area Meter (Li-cor Inc., Lincoln, Nebraska, USA).

Other resources

Appendix 1. Text description of phenological scale, Zadoks decimal code (DC).
Appendix 2. Picture description of phenological scale, Zadoks decimal code (DC).
Zadoks JC, Chang TT, Konzak CF (1974) A decimal code for the growth stages of cereals. Weed Research 14(6),415-421. doi: 10.1111/j.1365-3180.1974.tb01084.x

Notes and troubleshooting tips

Literature

Download complete manual: Protocols for cereal field experiments_Nov2012.pdf

Health, safety & hazardous waste disposal considerations