Plants and Temperature

1. Plants and Temperature Adaptability of (mostly) vascular plants to high and low temperatures and to the diurnal and seasonal periodicity of climatic factors

2. Investigating survival there is not any habitat in the world that would lack some moisture and light great capacity for adaptation in green plants (summits of mountain, deep forest shade, below water surface, spots where it never rains,) plant ecophysiology: first interest to humans because of agriculture (seed selection and breeding of plants tolerant of or resistent to climatic extremes) further interest in studying plant survival in different habitats (survival = measure of relative fitness)

3. Survival is the ability to tolerate local environmental conditions with the consequence of the selection of locally adapted forms It is easy to study plants, they mostly do not move from their habitats plant distribution: dispersal limitations are often more important than survival capacities DISTRIBUTION x SURVIVAL distribution of plants is affected by historical, geographical and environmental factors enabling the plants� survival.

4. Adaptation (genotypic) � Acclimatization (phenotypic) to have something special that increases the probability of survival of a certain genotype in its habitat ADAPTATION has to be heritable so we cannot speak about adaptation of one individuum In such cases it is better to use the word ACCLIMATIZATION (acclimation, hardening), which means individual adjustment to an environmental stress taking place in response to environmental conditions. Example: hardening of plants exposed to low temperatures

5. TOLERANCE: physiological: endurance of a plant is measuredin culture with no competition and only one variable being altered at a time ecological: response of a plant is examined under field conditions The tolerance of certain habitats relates to Ellenberg�s concept of a physiological and an ecological optimum for each plant genotype (taxon). The latter optimum is the result of competition, usually enabling a plant to materialize its physiological optimum only within certain limits.

6. Climatic boundaries CHILLING INJURY: tropical species suffer at temperatures of 6-10 �C for leaves; so-called chill sensitive plants (Coffea arabica, Oryza sativa, Citrus, Musa, Passiflora). Flowers and fruits are also sensitive. cellular dysfunctions, increase in membrane permeability, stopping of enzymatic activity.

7. Mediterranean distribution of the olive tree chilling injury to fruits is of little importance to the plants� survival, but the leaves are sensitive to chilling and that is a sufficient reason for the survival limitation

8. 2) FREEZING INJURY AND CRYOPROTECTION: the most known frost boundaries: when moving inland from the Mediterranean littoral, frost-free areas defined by the olive distribution, limited by water loss in winter frost resistance is genetically determined hardening of plants to freezing temperatures is a long and stepwise process, while de-hardening can last only 2-4 days hardening temperatures of +5 to 0�C enable a plant to withstand a moderate frost in winter, frost tolerance can increase in 1-2 days, with a full effect in 10 days dormant buds of leafy trees - the most resistant tissues root tolerance is lesser than that of aerial parts

9. ice crystals are not lethal as such if formed in the apoplast, the extent of frost damage is then dependent on desiccation resistance membrane holes cause irreparable damage rapid rate of thawing causes osmotic problems photosynthesis is the most affected by freezing, mainly the photophosphorylation mechanisms are affected membrane protection role of soluble sucrose when freezing temperatures occur (frozen potatoes, rose hips, sugar cane), trisaccharides are more effective than di-and monosaccharides sugar alcohols are also effective (mannitol, inositol, sorbitol, glycerol) halophytes use raffinose,which is not a part of primary metabolism amino acids: accumulation of proline, increase from 2-4 % to 60 %.

10. 3) SUMMER WARMTH: arctic species suffer from temperatures by 10 �C higher than is the mean summer temperature in their habitats They do not suffer from heat injury, but the problem is related to carbon imbalance in the plants These plants waste their carbohydrate reserves in summer and therefore are weak in the next spring Heat injury occurs in most plants at temperatures higher than about 40 oC. Extreme adaptation to high temperatures is found in thermophilous Cyanobacteria (70 to 85 oC) and Archaea (up to 95 oC) of hot springs

11. Periodicity Absorption rate of radiant energy in a place depends on its position in face of the Sun. Available energy is an environmental factor which periodically changes. The fluctuations of energy supply are reflected in periodical temperature fluctuations This periodicity affects all phenomena on the Earth, hence also any organism�s life. 1. Climatic rhythms 2. Rhythms of biological processes reflect climatic rhythms 3. Growth periodicity synchronised with climatic rhythms

12. Climatic rhythms DIURNAL CHANGES � (in plants) 1. day-night light changes lead to diurnal photoperiodicity 2. day-night temperature changes lead to diurnal thermoperiodicity temperature changes lag behind changes in radiant energy input, temperature maxima differ in dependence of thihs input. close to the equator: small differences in photoperiod while around the tropics: differences only of about 2 hours. Hence diurnal temperature fluctuations more important than the small seasonal ones wide temperature fluctuations especially in the mountains, both tropical and temperate ones SEASONAL CHANGES � at higher latitudes day and night lengths change dramatically during the year vegetative processes can be suppressed (dryness, cold)

13. Activity rhythms Diurnal light rhythm strongly influences plants. Photosynthetic capacity decreases in permanent light. Day-night temperature differences influence germination � evolutionary adaptation Best plant development when night T is by about 10-15 �C colder than day T For cacti and desert plants 20 �C difference optimal, for temperate zone plants 5 to10 �C difference optimal Exceptions: young spruces: no differences = the best tropical plants: only 3 �C differences inverse thermoperiodicity, warm nights: e.g., Pinus ponderosa and violets

14. Growth and development seasonality LIFE CYCLE: 1) plants with continuous growth short life cycles in many annuals, especially in ephemeral plants in deserts annuals or perennials in tropics 2) plants with intermittent growth growth at irregular intervals is safer (herbivores, parasites) growth or stillstand is regulated by environmental factors, mainly radiation input and temperature. Examples: forest floor ephemeroids, C3 vs. C4 plants

16. 3) vegetative and winter dormancy periods alternate: regularly changing seasons: changes in protoplasm, metabolic activity, developmental processes and tolerance of stress conditions aitionomous break � cycles without break, unfavourable environmental conditions enforce stillstand of metabolism cause breaks in growth (Senecio, Cerastium, Capsella)

17. 4) winter dormancy in trees of cold regions buds develop at the end of summer, during winter are dormant trees defoliate cambium is also dormant, other tree parts become resistant to cold and dehydration Three phases of winter dormancy: 1. predormancy - starts in buds before defoliation (decreasing daylenght � poplar, oak, beech, birch, willow, hazel, maple, larch, spruce) - low night temperature can replace short day (10 �C � ash-tree, chestnut-tree, cherry-tree, lilac) 2. true dormancy - starts in November, December, plants are unable to leave this rest period before end of dormancy - prolonged cold temperature leads to phase 3 (0 �C or less for 3-4 weeks � poplar, lime, maple, pine, fruit trees, grapewine)

18. 3. imposed dormancy rest period is coming to an end, gibberellins, cytokinins and auxin increase gene activation for basal metabolism, reserves mobilisation, biosynthesis and mitosis start ends in February, then development and growing start, depending only on the weather

22. Growth synchronisation with climatic rhythms tropics: limited by decreased water availability in dry periods others: activity synchronized with the vegetative period, photo- and thermoperiodism latitudes > 40� = days are longer than nights during the whole growing season, adaptation = long-day with respect to production of new shoots, leaves and flowers, a plant species is well acclimatized if the growing season is fully utilized, without risk of injury in the unfavourable season

24. Phenology indicator of weather characterisctics and climate changes beginning and duration of developmental phases vary from year to year phenology is interested in the processes of sprouting, flowering, fruit production and senescence historical science phenological dates: evidence of visible changes during the life cycle (start and end of the vegetation season, snow thawing, changes in colour of foliage)

26. phenological map of the start of lilac flowering in Europe as a signal of the start of spring

27. Dendrochronology shows annual growth rings and variability of climate annual ring phenometry phenometry = measuring duration of cambial activity and the type of wood formed (early, late) are affected by environmental factors spring wood indicates not only spring conditions but the nutritional status in the preceding year late wood indicates factors slowing down shoot growth and senescence of leaves

30. End of general part: Adaptability of (mostly) vascular plants to high and low temperatures and to the diurnal and seasonal periodicity of climatic factors