submitted in partial fulfilment
of the requirements for the Degree
Doctor of Philosophy
University of Canterbury
PIATERIALS AND METHODS
MORPHOLOGY AND DEVELOPMENT OF OOASE
AND BROOM PLANTS
IV.ACETYLENE REDLCTION BY E>CISED GORSE AND
Materials and Methods
METABOLISM AND TRANSLDCA nON OF FtXED NITROr:;EN
WITIiIN CIlRSE AND ffiOOM
A.Free amino acids in xyl ern sap and of
soluble nitrogen pool of root nodules
Free amino acids of sap
Free amino acids of nodules
8. 15N labelling studies
Metabolism of fixed 15N2
Translocation of fixed nitrogen
VI. EFFECT OF TEMPERA TURE AND LIG-iT ON rnOWTH,
NITROfIN ASSIMILAnON BY OORSE AND ffiOOM
Materials and methods
Results and discussion
VII. EFFECT OF PHOSPI-V\TE AND COMBINED NITROGEN ON rnOWTH
AND NITROfIN FIXATION BY OORSE AND ffiOOM
VIII. OXYGEN REQUIREMENTS AND THERMODYNAMICS OF SYMBIOTIC
NITROGEN FIXATION.THEORETICAL DISCUSSION.87
IX. OORON REQUIREMENTS FOR rnOWTH AND NITROfIN FIYATION
IN OORSE AND ffiOOM
~~terials and methods
Results and discussion
TRANSFER OF NITROGEN FROM OORSE AND EflOOM
GENERAL DIOCUSSlON. COT\CLUSIONS.
A C K N O V ~ E D G E M E N T S
TAB-ES, FIGURES, PlATES
A series of glasshouse and laboratory experiments was carried out
to enable comparison of two woody perennial legumes, gorse and broom, with
other legumes, nodulated non-legumes and other biological nitrogen fixing
80th species had distinct juvenile phases in which broom closely
resembled herbaceous species in appearance, but adult plants of both species
bore little resemblance to each other or to other legume species. Nodule
development was similar to that of other legumes, but mature nodules exhibited
structural adaptations to longevitymeristematic activity, a well
developed vascular system and numerous cytoplasmic granul es in cortical cells.
cant nued for muchonger
excision than has been observed in other legumes. In all experiments, broom
nodules exhibited higher rates of acetylene reduction and nitrogen fixation
than did gorse nodules.
The first detectable product of nitrogen fixation in excised nodules -
was rapidly incorporated into
~ - a m i n o
groups and another
unidentified fraction. The principle free amino acid in nodules and sap was
asparagine.Its preponderance incr88sed as plants aged.
Whole nodulated plants and excised nodules of both species exhibited
a relatively low temperature optimum for growth and nitrogen fixation (22oC).
They were very sensitive to elevated
Results indicated that
gorse and broom have relatively low light requirements.
When aeration was sufficient, combined nitrogen had little effect on
growth of nodulated plants.Nodulation in both species was reduced by
High levels ( 100 mg11) of nitrate
increasing amounts of combined nitrogen.
and ammonia caused consiQerable inhibition of nitrogen function.
80th species showed large respnses to phosphate, but were 6ble to grow
and fix nitrogen when supplied with low amounts of phosphate.