Seed storage behaviour of New Zealand's threatened vascular plants : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Horticultural Science at Massey University, Palmerston North, New Zealand
Loading...
Date
2013
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
At least 38% of New Zealand’s approximately 2300 vascular plant taxa (species and
subspecies) are threatened in situ and are vulnerable to extinction. It has become
increasingly important that a number of different complementary conservation
approaches and methods are used to insure against this loss of species. However,
limitations exist for the development of ex situ storage techniques due to a lack of basic
research on seed biology, including seed storage behaviour and germination
requirement of many rare and threatened species.
Seven New Zealand native species, Carmichaelia williamsii, Clianthus puniceus,
Clianthus maximus, Hibiscus diversifolius, Myosotidium hortensium, Tecomanthe
speciosa and Dysoxylum spectabile are a priority for investigation for ex situ
conservation strategies because of their conservation priority and lack of corresponding
techniques for their long term ex situ conservation. This study reports on seed storage
behaviour, dormancy mechanisms and potential ex situ conservation strategy including
conventional seed storage and cryopreservation of these New Zealand indigenous
species to facilitate germplasm storage.
C. williamsii, C. puniceus, C. maximus, H. diversifolius, M. hortensium and T. speciosa
were found to tolerate low seed moisture content (<5%) and thus can potentially be
stored for long periods under conventional seed bank conditions, whilst Dysoxylum
spectabile displayed essentially recalcitrant seed storage behaviour i.e. loss of viability
when desiccated below 25%. There is a need to consider alternative ex situ conservation
strategies, such as cryopreservation, to conserve this species.
Both C. maximus and M. hortensium displayed ‘essentially’ orthodox seed storage
behaviour i.e. tolerance to desiccation and low temperature. However, viability of M.
hortensium seeds declined after 12 months in all storage treatments and may be defined
as sub-orthodox.
This study demonstrated embryonic axis cryopreservation in D. spectabile using a
method based on rapid desiccation, encapsulation-dehydration and vitrification. This is
the first report of the successful cryopreservation of New Zealand native species. In D.
spectabile, encapsulation-dehydration or vitrification-based cryopreservation gave
higher levels of survival (20%) than rapid desiccation cryopreservation. However,
further optimisation of the protocol for plantlet recovery is needed to improve efficiency
before it can be considered suitable for conservation purposes.
It is essential to understand dormancy mechanisms and to have effective methods of
seed germination so seed banks can increase their efficiency and enhance their role in
biodiversity conservation. However, germination requirements for many native species
are either incomplete or not available. Unlike T. speciosa and D. spectabile, seeds of C.
williamsii, C. puniceus, C. maximus, H. diversifolius and M. hortensium were dormant
and that this dormancy was found to be of function of the seed coat. Dormancy in C.
williamsii, C. puniceus, C. maximus and H. diversifolius is a result of the seed coat
preventing water uptake by the dry seed. While physical constraint of embryo growth
by the seed coat is the cause of dormancy in M. hortensium seeds.
Description
Keywords
Rare plants, Endangered plants, Flowering plants, Vascular plants, Carmichaelia williamsii, Clianthus puniceus, Clianthus maximus, Hibiscus diversifolius, Myosotidium hortensium, Tecomanthe speciosa, Dysoxylum spectabile, Seeds, Viability, Seed storage, New Zealand