AGRO 3503

I. 2. Introduction: Terminology and botany of cereals.

 

Cereal crops are members of the Graminaceae (grass) plant family, one of the largest.   This unit will compare the similarities and differences of the grass family in relation to cereal crops. 

 

A. Terminology, facts.

cereal grains – the grain of cereal crops.

 

small grains – small seeded cereal crops such as wheat, oats, barley, triticale, rye.

 

food grains – cereals utilized for human consumption such as rice, wheat, rye and some millets.

 

feed grains – cereals utilized for animal consumption such as corn and grain sorghum.

 

cereal crops account for over half of the cultivated crop acreage.

 

corn – over 50% of world’s production is in the U.S.

 

rice – 95% world’s rice is produced AND consumed in Asian countries!

 

test weight – the weight of a bushel of grain adjusted for a set moisture percentage, ie.,

                     corn = 15.5% and wheat = 13.5%.  Basically a measure of grain density.

 

Factors related to test weights of harvested cereals:

            - species, variety

            - soil moisture, fertility

            - sunlight and growing conditions during grain fill

            - pest (insects, disease, etc) pressure, especially during grain fill

 

Botanical aspects of cereal crops.

 

1. cool season cereals: ie., wheat, oats, rye, barley, triticale. 

            - winter cool season cereal, ie., winter wheat – planted in fall, harvested in early

               summer.

 

            - spring cool season cereal, ie., spring wheat – planted in early spring, harvested

               in mid-summer.

 

2. warm season cereals: ie., corn, rice, millets, grain sorghum.  Planted in spring,

     harvested in fall.

 

3. Photosynthesis pathway: 

            - C3 cereals – have the C3 carbon pathway of photosynthesis.  Examples:  all

  cool season cereals.  Rice is the only C3 warm season cereal.

 

            - C4 cereals – have the C4 carbon pathway of photosynthesis.  All warm

               season cereals except rice are C4. 

 

     C4 cereals are more efficient dry matter accumulators because C4 plants have lower

     rates of carbon loss due to photorespiration. 

 

4. long-day cereals – cereals originating in more extreme latitudes where the day lengths

    are longer.  Examples: all the cool season cereals such as wheat, oats, rye, barley, etc.

 

5. short-day cereals – cereals originating near the equator where day lengths are shorter. 

    Examples: all the warm season cereals!

 

6. Nitro-negative cereals – high soil N levels may delay flowering, harvest time. 

     Examples: all the cool season cereals.

 

7. Nitro-positive cereals – high soil N may speed up the flowering process and

    result in earlier harvest.  Examples:  all the warm season cereals. 

 

8. vernalization – for cool season cereals.  A cool (chilling) period necessary to stimulate

    the flowering process.  This is basically several weeks of 45 F or cooler temperatures

    during vegetative growth (can occur at night) which trigger inflorescence extension. 

 

9. determinates – plants that grow vegetative, then enter into reproductive growth, ie.,

    distinct vegetative and reproductive growth.  ALL cereals are determinates.

 

10.  sigmoid growth curve – classic growth pattern of plants featuring a rapid, linear

       phase corresponding to internode elongation in grasses (Fig. 1).  Interesting too, this

        same growth pattern exists for grain filling in cereals. 

 

                                 early veg.       rapid linear             reproductive, grain filling

 

 

 


growth

 

 

 

 

 


                                                           time

 

11. drought evador – cereals that can delay flowering if under a drought stress. 

       Grain sorghum is the only cereal that can do this significantly.

 

12. tillering – new plants that sprout from the base of seedlings during a distinct

       tillering phase of growth.  Tillering is related to species, variety, soil fertility and

       plant density.  Plants tend to produce more tillers if plant density of low.  This is an

       important growth stage of most cereals in relation to final seed yields except for corn

       and grain sorghum, which don’t tiller much at all.

 

Reproductive aspects of cereal crops.

 

1. grass floret – the grass ‘flower’.  Highlights:

            - only one ovule per ovary.

            - two feathery stigmas per ovary.

            - three anthers per floret, except RICE, which has six!

            - the lemma and palea are modified petals and sepals.

            - florets are arranged on spikelets, which are arranged on inflorescences of

               three main types: spike (ie., wheat, barley), panicle (ie., rice, corn, grain

               sorghum) and raceme (mostly forage species).

 

Refer to the illustrations of the:

                                                            GRASS FLOWER

                                                            GRASS INFLORESCENCE

 

2. collar region – possesses a unique morphology related to species according to the

    presence, shape, size or absence of two main parts: ligule and auricles.

 

Refer to the illustration of the:    GRASS COLLAR