Merit barley is about a full leaf ahead of Whitebird wheat this week. This indicates that Whitebird requires more GDD for each leaf to develop than does Merit. Whitebird has 3 fully developed leaves and one tiller.
The number of tillers that develop is dependent upon both genetic and environmental factors. Some varieties are more free tillering than others. Barley is generally more free tillering than wheat. Stresses resulting from inclement weather, too little or too much water in the soil, soil compaction, deep seeding, or nutrients out of balance may all cause decreased numbers of tillers to develop. Very high seeding rates will also reduce the number of tillers/plant due to competition between plants.
Growing degree days for week of 5/3 - 5/9 = 83
Accumulated growing degree days (emergence to 5/9) = 360.5
Merit: 2-row spring barley. Picture taken 5/10/99 at the early tillering stage. Zadoks scale: 22, Feekes scale: 2, Haun scale: 4.3.
Merit:
2-row spring barley. Picture taken 5/10/99 at the early tillering stage (4 main stem
leaves, 2 main stem tillers, and coleoptilar tiller (T0) ). Zadoks scale: 22,
Feekes scale: 2, Haun scale: 4.3. Merit has 4 fully developed leaves and the 5th
is about 0.5 as long as leaf 4. The tiller (T1) developing at leaf 1 has one fully
expanded leaf and the 2nd leaf is also visible. Tiller 2 (T2) is developing
from the axil of leaf 2. Tiller leaves emerge from a sheath, called the prophyll,
which can later be found enclosing the base of the tiller.
The prophyll can be used to identify tiller leaves from those on the main stem or other
tillers.
Whitebird: soft white spring wheat.. Picture taken 5/10/99 at early tillering (3 main stem leaves and 1 tiller). Zadoks scale: 21, Feekes scale: 2, Haun scale: 3.4.
Whitebird: soft white spring wheat.. Picture taken 5/10/99 at early tillering (3 main stem leaves and 1 tiller). Zadoks scale: 21, Feekes scale: 2, Haun scale: 3.4.
Most important this week are things that are happening in the plants but are not yet
visible.
At this stage of growth, the head in the main stem has started to develop and can be seen under magnification. This is the stage when maximum number of kernels/head is determined. The maximum number of kernels for the main stem head will likely be finalized during this next week (barley only, wheat will take longer). Head development for tillers follows the same sequence as for the main stem, but is delayed in timing just as tiller leaf appearance is. Any stress during this stage will result in reduced yield potential. When temperatures are high through the tillering stage, yield potential is reduced. Moderate temperatures and shorter days (longer nights) will enhance development of more kernel buds on the head (florets) and gives potential for more kernels/head. At this point, the developing head is still below ground level. It will not start to rise in the plant until tillering is completed and jointing starts.
Also developing at this time but not yet visible in the pictures are the buds for adventitious roots. These roots develop from the crown nodes of the main stem and tillers, not from the seed as the seminal roots have. As adventitious roots develop, the plant will gradually become more dependent on them until they become the predominant root mass. Stress in the seedbed will inhibit development and growth of these important roots. They will likely be visible in the pictures next week.
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