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Home , Gossypium raimondii, Rosidae, Rosids

BIOL 317 LECTURE NOTES – WEEK 5 SUMMARY

ROSIDS: MALVIDS & FABIDS

Rosidae. Together with Asteridae, this contains most of the of . We have already covered several families of ; this week we will finish our treatment of rosid families.

Brassicales - (419 gen/4130 spp) – Mustard (or cabbage family). Also called “Cruciferae” - one of ten families that has two accepted names, this family gets its traditional name from the ‘cross-shaped’ petal arrangement. Brassicaceae includes many economically important e.g., oleracea - the following are “cultivars” arising from and maintained by artificial selection: var. capitata – cabbage; var. botritus – cauliflower; var. gemmifera - brussels sprouts; var. italica – broccoli; var. acephala – kale. (1) Herbaceous. (2) Glucosinolates – secondary compounds stored in vacuoles. These are released from the vacuole when damage occurs to the cell (e.g., from insects chewing on the leaf) and are altered by the enzyme myrosinase to produce compounds called isothiocyanates (“mustard oils”). Mustard oils give characteristic smell and taste. Secondary compounds in plants usually function to deter insect herbivores. (3) Flowers very uniform in floral structure - 4-parted actinomorphic calyx and corolla - stamens 6 (or many) often tetradynamous (4+2; 4 long inner and 2 short outer) in traditional Brassicaceae s.s. - carpels two, fused, ovary superior with a ‘replum’ (term for a false septum with thickened marginal rim, specific to this family), separating the two locules - ovules attached parietally to margins of replum - fruits typically a capsule called either a silicle (<2X longer than wide) or silique (>2X longer than wide). Some earlier-diverging members of the family have different types of flowers and fruits; these do not occur significantly in our area.

Arabidopsis thaliana is the most widely-studied model system in plants. It is fast- growing, easily propagated and maintained in laboratory settings, and has a small genome (5 chromosomes; 135 Mb). is the model for much of our knowledge of plant genetics, development, physiology, etc. Its complete genome sequence was published in 2000; the first plant genome sequenced.

Malvales - (204 gen/2330 spp) – Mallow family. Includes cotton, , , cacao. (1) Mostly herbs in North America; also shrubs and trees. (2) Leaves simple, palmately veined, often lobed or compound. (3) Stellate or branched hairs. (4) Mucilaginous cells (e.g., makes okra ‘slimy’); mucilage probably functions to deter insect herbivores. (5) Flowers 5 parted - stamens (5-) many, often +/- fused by the filaments into one or more clusters; when connate at the filaments to form a tube around the style then called monadelphous - ovary superior - placentation axile - carpels usually 5 (sometimes 2 or many) - fruit usually a capsule.

Domestic cotton - hirsutum - is tetraploid, believed to be of hybrid origin (resulting from a hybridization between an African and a S. American species). Polyploidy is common in plants, but complicates genomic sequencing efforts; the genome of what is believed to be a wild (diploid) precursor of domestic cotton () was published in 2012.

Malpighiales - s.s. (2 gen/485 spp) – , poplar family. Salix – ; – poplars, cottonwoods, aspen. The abbreviation “s.s.” stands for “sensu stricto”, latin for “in the strict sense”. Salicaceae has been expanded dramatically to include most of Flacourtiaceae, a primarily tropical family with much more diverse morphology. Salicaceae as covered here is monophyletic and is nested within Flacourtiaceae (similar to the Aceraceae derived from within ). Like Aceraceae/Sapindaceae, we will learn the characteristics of the smaller, derived group that is significant in temperate North America. (1) Shrubs and trees; vegetative reproduction by root sprouts (e.g., aspen groves) or rooting of branches (e.g.,willows along streams) is common. The largest single living ‘organism’ is an aspen grove in Utah (), nicknamed “Pando”. (2) Leaves simple, with ‘salicoid teeth’ (vein ending at tip of tooth with a small gland). (3) Dioecious - separate male and female plants. Pando is a male grove. (4) Flowers in catkins (both male and female) - fls borne in axil of hairy bracts on catkin-like axis (not always pendent) - no perianth (a gland or cup-like bract may be interpreted as calyx) - ovary superior, with 2-4 fused carpels with many ovules (different from and , which are inferior and with 1-few ovules) - fruit a capsule. (4) Seeds hairy - hence “cottonwood”. Not related to cotton!

Black cottonwood () is an important timber species, native to the PNW, and the foremost model system for studying woody plants. Its genome sequence was published in 2006; the first tree genome.

Malpighiales - (22 gen/950 spp) – violet family. (1) Herbs in temperate parts of the world, but most of the species of Violaceae are tropical trees. (2) Leaves simple (often cordate at base). (3) Flowers zygomorphic (bilaterally symmetric) - petals 5, the lower one forming a ‘spur’ - stamens five, the lower two forming a nectary (held within the petal spur) - ovary superior - placentation parietal - 3 fused carpels - fruit a capsule.

Violets often have two different kinds of flowers on the same plant: Chasmogamous - large showy flowers that typically are cross-pollinated. Cleistogamous - small inconspicuous flowers that don’t open and are self- pollinated in the bud. Both of these represent sexual reproduction, but one typically outcrosses and the other typically self-fertilizes. This way, violets can benefit from the advantages of both (reproductive assurance from selfing; genetic diversity from outcrossing).

Last two families are pretty closely related, even though they may seem rather different. They form an interesting contrast. In one, , the flowers are all pretty much alike, but fruit types differ greatly and form the basis of subfamilial divisions, whereas in the other, , fruit types are all similar - the legume - but flowers differ greatly and form the basis of subfamilies.

Fabales - Fabaceae (642 gen/18,000 spp) – or legume family. Also called “Leguminosae”, from the distinctive fruit which is characteristic of all its members. The third-largest family of plants; very economically important, contains many food species (pulses), as well as forage species, timber species, medicinal plants, gums, and dyes (eg. indigo). (1) Mostly woody tropical trees, but in temperate zone mostly herbs. (2) Commonly associated with N-fixing bacteria as symbionts in root nodules. This increases access to important nitrogenous nutrients, making legumes good colonizers of nutrient poor environments, and good cover crops or rotation crops. (3) Leaves usually compound - margins entire - stipules often present. (4) Flowers fall into three basic floral types - zygomorphic (subfams. and ) or actinomorphic () - sepals and petals in 5s - stamens: 10 unfused (subfam. Caesalpinoideae), 10 partly fused, 9 fused and 1 free (diadelphous) (subfam. Faboideae), or many unfused (subfam. Mimosoideae) - ovary superior - fruit a legume (specific type of follicle: dry, dehiscent fruit derived from a single carpel, opening along two lines of dehiscence).

The zygomorphic floral type is called a “flag” flower; it is most characteristic of Faboideae, in which the two lower petals are fused to form a “keel”. Caesalpinoid flowers sometimes have a “flag” form, but the lower petals are NOT fused and the stamens are NOT fused. Mimosoid flowers (actinomorphic) are called “brush” flowers, because they have many stamens that are exerted on long filaments and form a brush that covers visiting insects or birds with pollen.

Banner 1 free stamen

Flag Flower wing wing

9 fused stamens keel

Subfamily Caesalpinoideae is ancestral (paraphyletic) within the Fabaceae, and subfamilies Mimosoideae and Papilionoideae are monophyletic (derived from Caesalpinoid ancestors).

Rosales - Rosaceae (95 gen/2825 spp) – family. (1) Plants woody or herbaceous. (2) Leaves simple or compound (palmate or more commonly pinnate) - stipules usually present - leaves/leaflets often with serrate margins - alternate arrangement. (3) Flowers actinomorphic - sepals and petals in 5s - stamens many - hypanthium usually present - ovary superior, inferior, or half inferior.

Most striking variation in reproductive morphology is in fruit type. Traditional view of subfamilies is based on fruit type. Spiraeoideae: usually 5 free carpels (5 simple pistils) -> follicle : many free carpels (many simple pistils) -> aggregate fruits (unusual, accessory fruits in the case of and rose; achenes embedded in fleshy parts derived from swollen receptacle or hypanthium) : 1 carpel (1 simple pistil) -> drupe Maloideae: 2-5 fused carpels (1 compound pistil) -> pome (fleshy part derived from swollen hypanthium)

Traditional subfamilies Amygdaloideae and Pomoideae (Maloideae) are monophyletic; most of the species of Rosoideae form a monophyletic clade also. However, Spiraeoideae is paraphyletic, with Amygdaloideae and Maloideae derived within it.

For more practice with the concepts involved in phylogeny-based classification, try the supplementary exercises on Fabaceae and Rosaceae phylogeny and classification.

Pollination biology – Sexual Encounters of the Floral Kind (film) Pollinator specificity: (1) how likely are the hammer orchid (Drakaea) and bucket orchid (Coryanthes) to be pollinated by anything other than their wasp/bee? (2) What do you think the pollen:ovule ratio is like in these orchids? (3) How is this different to wind pollinated plants?

Orchids are well known for tight relationships with specific pollinators. Plants that are highly specialized for a specific pollinator have reduced chances to achieve pollination, because they cannot be pollinated by another agent. However, because pollination is very ‘targeted’, it is very efficient (hardly any pollen is lost in transfer). Thus, plants with highly specific pollinator relationships tend to have low pollen:ovule ratios. Wind pollination is not at all ‘targeted’; a great deal of pollen is lost in transfer, hence high pollen:ovule ratio in wind-pollinated plants.

Pollination ecology: (1) what motivates animals to visit flowers? (2) What are some ways that animals “cheat” plants? What are some ways that plants “cheat” animals?

Plants which are pollinated by animals (biotic pollination) usually have flowers which are showy (visual impact), and often fragrant; these function as advertisements to animals. The usual reward animals receive for visiting flowers is food, in the form of either nectar (nutrient-rich liquid, usually sugars) or pollen itself (rich in protein). Occasionally, animals receive some other benefit, such as wax in the case of specialized orchid-bee relationships, or even less tangible benefits, like warmth. Whether pollination is achieved is of no consequence to animal pollinators, and many animals will take pollen, nectar, etc. from flowers without transferring pollen. Many plants have ways to discourage non-pollinator visitors. These usually involve some degree of pollinator specificity (floral morphology targeted to specific type of pollinator), but many other interesting examples exist, eg. traps/obstacles, symbiotic ant guards, etc. Producing nectar/excess pollen is metabolically costly to plants, and some biotically pollinated plants do not provide any reward; eg. sexually-deceptive orchids, plants pollinated by carrion flies which mimic rotting flesh.

Pollination syndromes: (1) what do the flowers with nocturnal pollinators have in common? How do they differ? (2) What is buzz pollination? (3) What color and shape are flowers pollinated by hummingbirds? (4) Anigozanthus (kangaroo’s paw), Strelitzia, and Protea provide support for their pollinators to perch on, but Zingiber (ginger) doesn’t. Why? (5) How does a carrion fly-pollinated plant (Arum) attract pollinators? (6) Vallesneria is water-pollinated. What traits does it share with wind-pollinated plants?

A pollination syndrome is a suite of traits that have evolved in concert between different parts of a plant, and between different species of plants, that function to achieve pollination via a particular agent. Most plants are insect pollinated, and tend to have the following in common: flowers showy, with brightly colored petals; flowers usually with some food reward; flowers often with strong scent during the day; flowers often with ultraviolet markings visible only to insects.

Some more specific pollination syndromes include: Moth pollination – white flowers; opening and fragrant at night; long narrow corolla tubes with nectar at the bottom (only accessible by long-tongued moths). Bat pollination – white flowers; opening and fragrant at night; large and robust to support pollinator weight; stamens exposed and nectar easily accessible. With the ability to fly, bats are the most significant mammal pollinators. Buzz pollination – pollen shaken loose from anthers by ultrasonic vibrations, carried out by certain types of bees (mainly bumblebees). No nectar reward (pollen sole reward); connivent anthers (anthers held together) at center of flower; anthers opening by terminal pores. About 8% of flowering plants are buzz pollinated. Ant pollination – small, inconspicuous flowers; flowers close to the ground; very little nectar produced; small quantities of sticky pollen. Mostly in warm, dry, nutrient-poor habitats. Bird pollination – red or orange flowers; no scent; tubular corollas; large quantities of sugar-rich nectar. Bird pollinated flowers outside of the Americas usually have robust perches to support the weight of their pollinators. In the new world, hummingbirds are important pollinators; since they are able to hover, hummingbird pollinated flowers provide no perch. Carrion fly pollination – flowers reddish, purple or brown or greenish-brown; flowers close to the ground; scent strong and foul (like rotting flesh).

Other pollination syndromes involve a non-living agent (abiotic pollination). Wind pollination is the most common example. A few plants are water pollinated. Abiotically pollinated plants tend to have the following in common: flowers non- showy (perianth reduced or absent); no scent; no nectar; unisexual flowers; very high pollen:ovule ratio.

Revision: breeding systems & family ID: (1) the African water lily separates its sexual functions over time. Which sex comes first? What is the term for this? (2) How does the Arum maximize its chances of cross-pollination? (3) The arctic is a member of Rosaceae. What floral traits can you observe that are characteristic of the family? (4) Near the end of the film, the narrator talks about floral sex while images of dandelions are shown. What is the irony here?

Water lilies are protogynous, stigmas are receptive before pollen is released. This increases the chances of cross-pollination. The dead-horse arum of Sardinia (Helicodiceros muscivorus – “fly eating”!) is also protogynous. The species of Dryas shown in the film has actinomorphic flowers with distinct petals, many stamens, and many pistils. Dandelions are the best-known example of agamospermy in plants, producing seed asexually.