New Zealand Journal of Botany abstract
B97057Received 18 August 1997; accepted 9 March 1998
Effects of irradiance and nitrogen on Clematis vitalba establishment in
a New Zealand lowland podocarp forest remnant
RALPH A. BUNGARD*
Department of Plant Science
P.O. Box 84
Lincoln University
Canterbury, New Zealand
JAMES D. MORTON
Animal and Veterinary Sciences Group
P.O. Box 84
Lincoln University
Canterbury, New Zealand
DAVID L. MCNEIL
GAVIN T. DALY
Department of Plant Science
P.O. Box 84
Lincoln University
Canterbury, New Zealand
*Present address: Department of Animal and Plant Sciences,
University of Sheffield, Sheffield S10 2TN, UK.
email: r.a.bungard@sheffield.ac.uk
Abstract The influences of light and nitrogen (N) on growth
and physiological characteristics of C. vitalba seedlings were
investigated in a New Zealand lowland podocarp forest remnant. Seedlings
planted within undisturbed forest did not persist, even when supplied with
additional nutrients, whereas seedlings planted outside the forest not only
persisted but, with additional nutrients, achieved substantial growth. Under
controlled conditions with irradiance over a range from full sunlight (100%
Ir) to 1% full sunlight (1% Ir), seedlings achieved maximum
growth at 100% Ir, substantial growth as low as 10% Ir, and
little growth at 3% Ir. Seedlings at 1% Ir did not survive. The
influence of irradiance on seedling growth is compared with light acclimation
characteristics; seedlings at low compared with high irradiances had a lower
chlorophyll a:b ratio, lower concentration of total carotenoids
and soluble protein per unit leaf area and chlorophyll, and a greater
shoot:root (S:R) ratio, specific leaf area (SLA), chlorophyll concentration per
unit leaf area and dry mass, and xanthophyll cycle pigments (V+A+Z) and
ß-carotene as a proportion of the total carotenoid pool. Limited growth
or survival at irradiances <3% Ir under controlled conditions and
when seedlings were planted within undisturbed forest suggests that low
irradiance is the primary factor limiting establishment within undisturbed
parts of the forest remnant.
At higher irradiances near the forest margin, a similar increase in growth
when seedlings were supplied with N or N plus base (P, K, S, Ca) fertiliser
suggest that N is the major nutrient limiting growth in this forest remnant.
Seedlings also showed a substantial growth response to applied N (as
NO3-) under controlled conditions; increased growth coincided with
increased nitrate reductase activity (NRA) and concentration of NO3-
in plant tissue.
The results are related to other work that reports on the distribution of
C. vitalba in the same forest remnant and the influence of light and N
on seed germination. We suggest that germination and growth in response to
light and N can account for the pattern of establishment and success of C.
vitalba in this native forest remnant.
Keywords Carotenoids; chlorophyll; Clematis vitalba;
light; forest remnant; nitrate reductase; nitrogen; soluble protein;
xanthophyll cycle
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