Lecture 6- Myrtaceae and Eucalypts

Question 1

How many species are the in the family Myrtaceae?

Answer 1

-3000 spp. worldwide -1650 in Australia -large family, includes eucalypts -the number is number of genera, largely southern hemisphere Gondwanan group -the spread from there to northern hemisphere (limited)

Question 2

What are Myrtaceae and what are they used for?

Answer 2

• In Australia: bottlebrushes, tea trees, paperbarks, lilly pillies; eucalypts dominate forests and woodlands • Used traditionally for wood for canoes, bark, honey, water (mallee roots) • Modern uses- horticulture, timber, paper, oils, spices - cloves (Syzygium aromaticum flower buds) • Fruit - scrub cherries, Guava, Feijoa!

Question 3

What are the characteristics of family Myrtaceae?

Answer 3

• All have leaves with aromatic oils in oil glands • Anti-herbivory; increases flammability -the yellow dots are glands full of oil -basically cavities in a leaf lined with cells that secrete the oil

Question 4

What are the fruits of Myrtaceae like?

Answer 4

1. Dry-fruited forms e.g. eucalypt capsule opens by valves (splitting of top of ovary), protected from fire 2.Fleshy-fruited forms e.g. rainforest lilly pilly -flowers are mostly stamens= the ornamental part that attracts pollinators -some species have fleshy fruit (only few) -the fleshy good tasting fruit occur in the rainforest

Question 5

What are the flowers of Myrtaceae like?

Answer 5

• Flower regular in shape, 4-5 sepals, 4-5 petals
• Many stamens
• Inferior ovary,the ovary is on the bottom

Question 6

What are the flowers of Myrtaceae like when folded?

Answer 6

• oil glands present in the reproductive parts too= anti herbivory function, can be fragrant and part of attraction to pollinating organisms
• can have different composition of the oil in different parts of the same plant
• top of the ovary= tissue that produces nectar= collects and attracts pollinators

Question 7

What colour are tea tree flowers and what pollinates them?

Answer 7

•White, open flowers • Pollinated by flies, beetles, bees

Question 8

What are bottlebrushes pollinated by?

Answer 8

-red coloured flowers, red stamens so pollinated by birds or by honey possum

Question 9

How many species of eucalypts are there in Australia?

Answer 9

-700+ -forest, woodlands, and mallee shrublands

Question 10

Where do eucalypts occur?

Answer 10

-All habitats except rainforest, alpine and arid desert

Question 11

What are eucalypts used for?

Answer 11

-extremelly important ecologically •Timber - building, furniture E. marginata (jarrah) WA E. regnans (mountain ash) EA •Pulp for paper •Fuel •Oils •Ornamentals •Reforestation of degraded land e.g. red gums, blue gums in salted areas •Habitats for animals e.g. hollows in tree trunks for possums

Question 12

What are the characteristics of the Mountain Ash? (eucalypts)

Answer 12

-The tallest flowering plant in the world - 100+ m height, 400 years old, nest hollows a resource for animals -After fire, regenerates from seed stored in canopy in woody fruits! adult plants killed by the fire -then regenerate from seeds and grow very quickly -means that all the trees in the same area will be approximately the same age as they date to the same fire disturbance

Question 13

What are the genetics of Eucalypts?

Answer 13

-DNA data show two major lines of evolution, three genera Eucalyptus named in 1789 Collected on Cook’s 1st voyage Corymbia, bloodwoods named in 1995

Question 14

What is the fossil record of Eucalypts?

Answer 14

-Flowers & Fruits 30 mya -Pollen 60 mya -history- prevalent in australia now, have a patchy fossil record, maybe due to where they grew -have been in Australia for a long time, at least 30 MY maybe 60 MY -don’t occur in S. America at present but probably did prior to the breakup of Gondwana

Question 15

What are the eucalypts’ rainforest relatives and what do they tell us about eucalypts?

Answer 15

-3 related rainforest genera to the eucalypts -morphology that is ancestral to eucalypts so can tell us how they evolved

Question 16

What is the spread of the 3 Eucalyptus genera in Australia?

Answer 16

-

Question 17

What do Eucalyptus flowers look like?

Answer 17

• they don’t have typical petals and sepals -instead have a protective cap= the operculum falls off, equivalent to the petals and sepals, just fused together
• modified sepals and petals sometimes have more caps
• the upper is the sepaline as it is equivalent to sepals
• the other one is petaline

Question 18

What is the Eucalypt flower and fruit development?

Answer 18

• male phase first
• after that stamens fall off and stigma becomes receptive to pollen
• prevents inbreeding

Question 19

How are eucalypts pollinated?

Answer 19

-Eucalypt stamens and nectar attract insect and bird pollinators -ants in some flowers, can get access to nectar, not good pollinators, usually not classified as such

Question 20

What is Eucalypts fruit good for?

Answer 20

• woody capsule aids species identification
• peduncle= stalk supporting a cluster of flowers disc= top of the ovary, the nectar secreting it used to be that

Question 21

Why is there such a low success rate of eucalypt seeds?

Answer 21

-mature and dry up, open and release the seeds -low establishment of new individuals -the seeds are papers and ants harvest them and eat them which kills them -often the environment is also not inducive to new seedlings -then after fire they fall and more than ants can eat so lot of new seedlings

Question 22

What is the Eucalypt foliage like?

Answer 22

• have distinctive foliage at various life stages the adult ones hang down in vertical fashion -so in the hottest part of the day they expose only a small area to the sun -reduced the probability of overheating and reduced water loss -

Question 23

What is the anatomy of Eucalyptus adult leaf?

Answer 23

• isobilateral anatomy
• pallisade mesophyll= where chloroplasts
• they are on both sides as they are exposed to the sun at different times of the day= isobilateral anatomy
• adult leaves are not opposite one another

Question 24

What is Eucalypt juvenile foliage like?

Answer 24

• often leaf opposite, sessile, held horizontally, dorsiventral anatomy -juvenile leaves are not alternating on the stem, they are opposite, they are flatter and don’t hang downwards -the pallisade mesophyll is only on the upper surface =dorsoventral anatomy -there is a high pressure on juvenile tree to outcompete the others and grow quickly -also lighter in colour so they don’t overheat and are waxy

Question 25

Do some Eucalyptus species retain juvenile foliage throughout life?

Answer 25

-yes

Question 26

How do you identify Eucalypts?

Answer 26

1.Fruit shape and size 2.Bark type 3.Leaf shape and size (including juveniles) 4.Flower bud shape/number