Botany

Last updated February 23, 2014

ORIGIN and SPECIES

Worldwide, most of the cultivated wheat varieties are hexaploids (Triticum aestivum) There are some cultivated TETRAPLOIDS, most notably T. durum Annual or winter annual grass

ADAPTATION

TEMPERATURE

Wheat is a cool season crop

Not widely grown in warm, humid regions because of diseases

Has a slightly higher heat requirement and a slightly longer growing season than other small grains

Minimum growth - some winter wheat will grow at temp's as low as 38 F

Ideal temps: Daytime highs of 70‑80oF

Winterhardiness (cold tolerance) Rye > wheat > barley > oats 

Length of growing season

Winter grains: Wheat > Rye

Spring grains: Wheat > Oats > Barley

MOISTURE

  • Most wheat grown in areas that have 15‑35" annual precip
  • Some grown in areas with < 10" annual precip by alternating with SUMMER FALLOW USA -  N.DAK. Australia
  • Timing of precip
  • Important for both winter and spring wheat
  • Early season moisture is critical for both W and S types

SOIL

  • Best suited to fertile, medium‑to‑heavy textured soils that are well‑drained
  • Does poorly on sandy, acid soils that are poorly drained
  • Wheat can have problems with aluminum toxicity in low pH soils
  • Aluminum tolerant cultivars have been developed

Vegetative characteristics

Similar to other small grains

  • alternate leaf arrangement, etc
  • small auricles

Roots

  • Fibrous root system
  • seminal, crown, and brace roots
  • Winter wheat - more extensive root system than sp wheat
  • Wheat - deeper rooting than barley and oats, not as deep as rye

Pubesence

Reproductive characteristics

Infloresence = Spike

  • One spikelet per rachis node with 3 or more florets/spikelet 2 primary florets
  • outer 1 secondary florets
  • inner
  • Spikelets are subtended by two glumes
  • Glumes - thick - important in classification

Many varieties are awned (awn- extends from lemma)

  • Photosynthesis (PS) occurs in awns
  • Awns contribute to grain yield in semiarid conditions, but usually not in more humid conditions
  • Semiarid conditions
    • lower leaves dry up early, so awns compensate for this loss in leaf area and ps.
    • Awns may increase yields by 5-10%
  • More humid conditions - contribution of awns is insignificant when compared to ps from leaves

Pollination

  • Begins in the central part of the spike
  • Proceeds upward and downward over a period of 2‑3 days
  • Wheat is normally self‑pollinating, but cross‑pollinating lines have been developed
  • Several companies have worked extensively with hybrid wheat, but hybrids are not yet widely grown
  • Although hybrids in some areas of the US have performed very well, they have not consistently outyielded the best pure line
  • Hybrids have to outyield the best pure lines by 15-20% to be economically feasible
  • Wheat is free threshing

Kernel parts:

Kernels of wheat species and varieties differ according to 
  • Size
  • Shape
  • Color
  • Texture
  • Hardness vs softness
    • Hard = vitreous
    • Soft = nonvitreous
  • Crease width and depth


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