2. The Wheat Plant

Development, Growth, and Yield

By Gregory S. McMaster and W.W. Wilhelm

Final grain yield is the result of developmental and growth processes of the wheat plant from seed germination through grain maturity. Knowing the sequence and timing of events during wheat development helps us understand how yield potential is determined, assess how the plant “perceives” its environment, and improve management practices through the prediction of future crop growth stages. Wilting and tissue color change are common signals indicating water or nutrient stress, which, combined with knowledge of how the wheat plant develops, can provide ways to estimate the outcome of yield-impacting situations. This, in turn, can guide the selection and application of management tools to minimize reductions in yield and profitability. This chapter describes the yield components of wheat, how the wheat plant develops, how yield potential is determined, and methods to predict when certain growth stages are reached under water-stressed and non-stressed growth conditions.

The wheat plant is remarkably resilient and flexible in forming final yield because it can take alternative paths in reaching a given level of productivity. The following five yield components determine yield potential:

1. Plants per unit area (acre)
2. Number of heads (spikes) per plant
3. Number of spikelets per head
4. Number of kernels per spikelet
5. Kernel size

Healthy wheat crop.

Figure 2.1. Healthy wheat crop.