Blog search results for Tag: agriscience,

Sustainability & Environment

Gardens and parks provide visual evidence of climate change. Regular observation shows us that our flowering bulbous plants are emerging, growing and flowering. Great Britain is particularly rich in long term recordings of dates of budbreak, growth and flowering of trees, shrubs and perennial herbaceous plants. Until recently, this was dismissed as ‘stamp collecting by Victorian ladies and clerics’.

The science of phenology now provides vital evidence that quantifies the scale and rapidity of climate change. Serious scientific evidence of the impact of climate change comes, for example, from an analysis of 29,500 phenological datasets. This research shows that plants and animals are responding consistently to temperature change with earlier blooming, leaf unfurling, flowering and migration. This scale of change has not been seen on Earth for the past three quarters of a million years. And this time it is happening with increased rapidity and is caused by the activities of a single species – US – humans!

 2 iris

Iris unguicularis (stylosa). 

Changing seasonal cycles seriously affects our gardens. Fruit trees bloom earlier than previously and are potentially out of synchrony with pollinators. That results in irregular, poor fruit set and low yields. Climate change is causing increased variability in weather events. This is particularly damaging when short, very sharp periods of freezing weather coincide with precious bud bursts and shoot growth. Many early flowering trees and shrubs are incapable of replacing damaged buds, as a result a whole season’s worth of growth is lost. Damaged buds and shoots are more easily invaded by fungi which cause diseases such as dieback and rotting. Eventually valuable feature plants fail, damaging the garden’s benefits for enjoyment and relaxation. 

Plant diseases caused by fungi and bacteria benefit from our increasingly milder, damper winters. Previously, cooling temperatures in the autumn and winter frosts prevented these microbes from over-wintering. Now they are surviving and thriving in the warmer conditions. This is especially the case with soil borne microbes such as those which cause clubroot of brassicas and white rot, which affects a wide range of garden crops.

 3 Hazel

Hazel (Coryllus spp.) typical wind-pollinated yellow male catkins, which produce pollen.

Can gardeners help mitigate climate change? Of course! Grow flowering plants which are bee friendly; minimise using chemical controls; ban bonfires – which are excellent sources of CO2; establish wildlife-friendly areas filled with native plants and pieces of rotting wood, and it is amazing how quickly beneficial insects, slow worms and voles will populate your garden.

Professor Geoff Dixon is the author of Garden Practices and their Science, published by Routledge 2019.

Agrifood

Understanding organisms’ capabilities of sensing environmental changes such as increasing or declining temperature is becomes ever more important. Deciduous woody trees and shrubs growing in cool temperate and sub-arctic regions enter quiescent or dormant states as protection against freezing temperatures.

These plants pass through a two-stage process. Firstly, they gradually acclimatise (or 'acclimate', in the USA) where lowering temperatures encourage capacities for withstanding cold. This is a reversible process and if there is a spell of milder weather the acclimatisation state is lost. This can happen, for instance, with a fine spell of 'Indian summer' in October or even early November.

winter weather and dormant trees

Winter weather and dormant trees. All images by Geoff Dixon

Where acclimation is broken, plants become susceptible to cold-induced damage again. If acclimation continues, however, plants eventually become fully dormant. This is not a reversible state and only ends after substantial periods of warming weather and increasing day-length. Some plants will require an accumulation of 'cold-units' – ie, temperatures below a specific level before dormancy is broken.

Detailed research information is accumulating to describe how acclimatisation develops. Changes take place that strengthen cell membranes, possibly by increasing the bonding in lipid molecules, and causing alterations in respiration rates, enzyme activities and hormone levels.

non-acclimatised azalea (front), acclimatised azalea (back) 

Non-acclimatised azalea (front), acclimatised azalea (back).

Leaves in a non-acclimated state will leak cellular fluids when they are chilled, whereas acclimated leaves are undamaged. These processes result from an interaction between genotype and the environment. Cascades of genes come into play during acclimation and dormancy. 

The genus Rhododendron offers a model for studies of these states. Some species originate from alpine environments, such as R. hirsutum coming from the European Alps and one of the first English garden 'rhodos'. By contrast, plants of R. vireya come from tropical areas such as the East Indies.        

comparing the leakage of cellular fluids in acclimatised and non-acclimatised rhododendron leaves subjected to -7oC 

Comparing the leakage of cellular fluids in acclimatised and non-acclimatised rhododendron leaves subjected to -7°C

Practical outcomes from studies of acclimation and dormancy are twofold. Firstly, are there substances that could be sprayed onto cold susceptible crops, eg potatoes or cauliflowers, that prevent damage? This is so-called 'anti-freeze chemistry'. Some studies suggest that spraying seaweed extracts will dimmish damage. The downside of this approach is that rain washes off the application. Secondly, identifying genes which increase cold hardiness offers possibilities for their transfer into susceptible crops. Gene-editing techniques may offer means of tweaking existing cold-hardiness genes in susceptible crops. 

Professor Geoff Dixon is the author of Garden Practices and their Science, published by Routledge 2019.