Physiologic responses of Bromus inermis

123 Pages·012.91 MB·English

by  Metcalfe, Darrel Seymour

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HERftlGLCSIC W P O K li OF 8EGII0S 1RBBHX8
Darrel Seymour Ifeto&lf®
A Dissertation Submitted to the
Graduate Faculty ia Partial fulfillment of
Si® Requirements for the Degree of
DOCfOE OF JBIhOSOlffir
Major Subjects s Crop Produotioa
Plant Physiology
Approved *
W m oi >
lorn State College
. . - 1950- • -
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UMI Number: DP12492
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®»spoas@ of Plants to fhotoperiod **»*.*.».*♦»*.»*.«*...... 3
Influence of Sitrogen Fertilizer on Seed and Forag#
Yields ................................................ 7
Effeot of Clipping Treatments on Seed and Forage Yields ... 11
Effect of Clipping Treatments on Organic Food Kesonres .... 14
UtfUtXAX* MB iSBSSODS ..... 17
Greenhouse ExperinsBnts 17
Fertiliser and Clipping &p®ri8»ts in the Field ...... 18
Seasonal Food Reserves .................................... 26
m mrn x w u L . wmiaas so
Besponse to Photoperiod and Other Treatments in
the Cfceenhonae 50
Tillering ............................ 52
Yields of tops and roots .............................. 57
Flooring ............................................. 40
Effect of nitrogen Fertiliser and Clipping Treatments
m. forage Yield* in the Field .... 47
Effect of nitrogen Fertiliser and Clipping 'Treatments
os Seed Yield in the Field .................. 67
Humber of panicles 88
Ifcimbsr and fertility of florets ....................... @1
Baalole length 65
Weight of .seed per panicle ............................ 68
Seed yields ........................................... 72
lesens® Foods 81
Greenhouse samples .................................... 81
Field samples 82
siactssioi ....... m
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iMficwetioi
' Saoofch broaegrass (Brorsus iLmerail® Leyss) ms introduced into the
United State® la'1884.''Broraegrass las a wide■rang© of adaptability.
It* rofistaaoe'to ®xtfe»s of'drought «ad berapimtur©, made evident to
lorn farmer® during the drought year® 1954 and 1956, won for it favor­
able consideration. 3he plant is a long-lived pareimial that under
normal conditions fora* a dense sod* spreading moderately % mans of
small rhizomes with may fibrous roots* 3h# extensive root system
penetrates five feet -deep or more, the stems range from about two to
four feet ia height. Plant® are leafy and palatal?!© t© livestock, even
at advanced stages of maturity, md whoa abundantly supplied with plant
nutrients, ©specially nitrogen, are highly productive* Si# seed are
predated in open paniclesj they are long, flat, and chaffy, reseabllag
©at® but mah smaller.
Seed production of some of the more important forage crops, includ­
ing smooth broaegrass, has declined seriously in the past two decades,
Curing the m r years when the row crop acreage ms increased the demand
for seed'was small* With a return to more forages for fertility main­
tenance and erosion control, however, the need for high quality seed
is urgent.
Bromegrass seed has been produced ia the northern United States and
Canada, but with the increased prominence of the southern type, seed
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2
*
production lias been emphasised in febraska and Mas®.#, and to & lessor
degree la Iowa* Although climat® and soil conditions favor brwgsms®
seed production ■ in western. Iowa * high seed yield# are possible la most
sections of the state. Supplies of bromsgmss seed, particularly the
southern type* are short and prices bam risen sharply* With an in­
creasing demand for locally gyem* well adapted seed, bron© grass seed
production offers an opportunity for cash returns fro® land in grass*
this return is of particular interest to the farmer who mat keep part
of Ms land la grass for fertility aaiateaaaoe and erosion control but
who Ms Insufficient livestock to utilise all of it.
Bvomegr&a# seed yields tend to decrease rapidly in older stands.
When seeded alene yields decrease sartorially even in the second harvest
year* ' When s eedod with a legume yields may be maintained for two to
four years or longer* Bven old stands boeom© potential Seed sources
when practical and economical treatments are used to keep such area#
productive.
fhe presort study ms undertaken to find methods of increasing
seed and forage yields. It stresses the effect of nitrogen fertiliser
and of clipping ©a seed and forage yields, and' includes greenhouse
studies of the fundamental problems of floral initiation in bromegras®.
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s#
WSfim Of JBRSIHENT LlfEMfUB
Besponse of Plants to Htotoperied
imitsk (45) has suwaari*#d, with an extensive bibliography, the
biochemical studies of photoperiodism in plants. the symposium on
photoperiodism by Ifameek and Whyte (46} gives a comprehensive list of
research workers and their aoeoaplistaTOts, with theories of photo*
periodism, Sarwr and Allard in 1920 (22) discovered that soa® plants
flowered sooner when the days were short and that others blossomed only
when the days mm long* the flowering of still others ma not influ*
©need by length of day. They reported that the factor of day length
profoundly influences plant development. In 'later studies (2i) they
first suggested the tew photoperiodism to designate these effects of
length of day, and classified numerous species as ’’short day** or ’’long
day” on the basis of the day length refuirei for mximum flowering sal
fruiting.
Withrow -sad Benedict (69) studied greenhouse annuals sad feast W
foot candles of light sufficient for naxiata response when adding light
beyond the natural day length. Parker and Borthwiek (SB) and Earaner (28)
studied day length and crop yields. When lo»g*day plants are grew, under
a normal summer day length of 16 hours or more heading is induced*
Bob®its and Struolssasyer (55) observed the interaction of the two
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4,
factors photoperiod and temperature, In later studies they (§6) ob­
served that a large number of species grown in Img-day mi short-day
mwivmmn^s haw different photoperiodic responses, at different temper­
ature®* Their list includes reed oanarygrass, qu&ckgrass, Kentucky
bluegfas®* and timothy*
Mum' (44), while studying floral initiation in iMmtfatua peaaaylv&a-
icum. a short day plant# found that temperature during induction has
ft pronounced influence on flowering* Ascending to llyte (85) temper­
ature i# an accessory factor in photoperiodism. Under low temperatures*
photoperiodic treatment may lead to the foraaiioa of the (still hypo­
thetical) flowering hormone or to its- preliminary stage* which cannot
be operative* however* until there is a higher temperature,
Withrow (68) concludes that external nitrogen supply is act as de­
termining a factor in floral initiation m photcpericiisa or t«ap®»twre*
but that time' and appearance of flowers are altered by it in sow species*
md that adequate fertilization results in mere flowers then the photo-
period is favorable* Borthvriok (10) reported an interaction of nitrogen,
fertilisation and photoperiod.
Stmne tod'Allard (If) studied strains of timothy ranging from very .
early to very late in time of flowering under natural conditions* They
found that the later strains required longer day lengths for flowering*
Olmsted (SO) reported that Bouteloua gracilis* a perennial of the temperate
sons* behaves as & long-day plant* Benedict (6) studied four prairie
grasses and found that these species could be induced to flower in the
greenhouse ia the winter by controlling day length ©ad temperature.
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