Pittosporum tobira

Pittosporum tobira is a species of sweet-smelling flowering plant in the pittosporum family Pittosporaceae known by several common names, including Australian laurel,[1] Japanese pittosporum,[1] mock orange[1] and Japanese cheesewood.[2] It is native to Japan (south of Kanto), China, Taiwan, and Korea,[2][3] but it is used throughout the world as an ornamental plant in landscaping and as cut foliage.

Pittosporum tobira
Leaves and flowers of P. tobira
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Apiales
Family: Pittosporaceae
Genus: Pittosporum
Species:
P. tobira
Binomial name
Pittosporum tobira

Description
Pittosporum tobira fruit in Hampyung, Korea

It is an evergreen shrub which can reach 10 m (33 ft) tall by 3 m (10 ft) broad,[3] and can become treelike. It can also be trimmed into a hedge. The leaves are oval in shape with edges that curl under and measure up to 10 cm (4 in) in length. They are leathery, hairless, and darker and shinier on the upper surfaces. The inflorescence is a cluster of fragrant flowers occurring at the ends of branches. The flower has five white petals each about a centimetre long. The fruit is a hairy, woody capsule about 1 cm wide divided into three valves. Inside are black seeds in a bed of resinous pulp.

Distribution

It is native to parts of Eastern Asia but has been introduced as an ornamental plant in many parts of the world. In China, it is found in the Fujian province and has been introduced in several others. In Japan, it is found in Honshu and the islands of Kyushu, Shikoku, as well as the Ryukyu Islands. It is also found in South Korea and northern Taiwan.[4][1]

It grows in forests, limestone areas, slopes, sandy seashores, and roadsides, usually to 1800 m sea level.[4]

Taxonomy and phylogeny

P. tobira is one of over 200 species of the genus Pittosporum which also includes kōhūhū and tarata. Phylogenetic research suggests P. japonicum , P. glabratum , P. illicioides, and P. balfouri are closely related.[5][6]

Names and Etymology

The binomial qualifier tobira derives from the Japanese name for the plant. The genus name Pittosporum derives from the Greek substantives pitta (meaning "pitch") and sporos (meaning "seed") in reference to the resinous substance that surrounds the seed.[7]

In Japan and China, where it is native to, it is known as tobera (トベラ in Japanese) and hai tong hua shu (海桐花属 in Chinese). It's Japanese name, tobera, comes from "tobira no ki" which roughly translates to "door tree". This is because the plant emits a foul order when leaves or branches are cut and so it was hung up in doorways during Setsubun along with the heads of sardines.[8]

In English, it is known as Japanese pittosporum, mock orange, Australian-laurel, and Japanese cheesewood.[2] In German it is also known as chinesischer Klebsame ("Chinese sticky seed") or Pechsame ("bad luck"). In Swedish it is called glansbuske ("glossy shrubs"). In Brazilian Portuguese, it is known as lágrima-sabéia ("teardrop"), pau-de-incenso ("incense stick"), or pitósporo-japonês.[1]

Chemistry
Pittosporum tobira seeds
Nutritional value per 100 g (3.5 oz)
Energy385.65 kcal (1,613.6 kJ)
71.25 g
5.61 g
12.54 g
MineralsQuantity %DV†
Calcium
14%
140 mg
Iron
23%
3.05 mg
Magnesium
104%
367.47 mg
Manganese
51%
1.08 mg
Potassium
15%
723.36 mg
Sodium
2%
26.01 mg
Zinc
21%
2.01 mg
Other constituentsQuantity
Water8.02 g
Caffeic acid3,857 mg
Ferulic acid2,007 mg
p-coumaric acid1,285 mg
†Percentages are roughly approximated using US recommendations for adults.

Although not typically considered edible, the nutritional composition of P. tobira seeds have been analyzed. The seeds are mostly carbohydrates (71.3%) while their low fat content (5.6%) means it cannot be classified as an oily seed. The high ash content may suggest the presence of considerable amounts of inorganic nutrients in this plant.[9]

The total phenolic content was 102.7 mg gallic acid equivalents per gram (GAE/g) while the total flavonoid content was 31.62 mg of catechin equivalent per gram dry weight basis (CAE/g DW).[9]

An HPLC analysis revealed the presence of five phenolic acids with caffeic acid being the most numerous (38.57 mg/g). The next most common phenolic acids were ferulic acid (20.07 mg/g), p-coumaric acid (12.85 mg/g), cinnamic acid (5.14 mg/g), and gallic acid (1.03 mg/g). Nineteen components were found to makeup 89.5% of the total essential oil content with oxygenated sesquiterpenes being most present (57.5%) followed by sesquiterpene hydrocarbons (11.8%) and oxygenated monoterpenes (6.7%). Spathulenol was the most representative component (48.0%), followed by isospathulenol (5.8%), δ-Elemene (4.2%), λ-gurjunene (4.0%) and camphor (3.7%). Additionally, it was found that P. tobira seed essential oils exhibited important antioxidant activity.[9]

Methanol extracts of P. tobira was found to control more than 90% development of rice blast, an important rice pathogen for commercial rice production, at 1,000 μg/ml.[10]

Cultivation and uses

This shrub is a common, drought-tolerant and fairly hardy landscaping plant. Many cultivars have been developed, including dwarf forms and the popular 'Variegata', which has variegated leaves.[11] It is used for hedges, living privacy screens, and indoor and outdoor planter boxes.[11] The stems, leaves, and dried fruits are used in flower arrangements.[11]

P. tobira is suitable for a Mediterranean climate, but may be more sensitive than other common ornamental plants to drought-induced stress. In 2014, a study comparing the effects of drought stress of five common ornamental plants found P. tobira to be the only plant who's total dry biomass was significantly affecting (noting a 19% decrease in biomass).[12] The plant may also be useful for fire-resistant landscaping due to its high gross heat of combustion.[13] This plant may also be associated with more damage to other plant species when it is nonnative. A 2016 analysis of 49 plant species in green spaces in Madrid found P. tobira to be among some of the most likely shrubs to be associated with damage to native plant species.[14]

The species[15] and the cultivar 'Variegatum'[16] have both gained the Royal Horticultural Society's Award of Garden Merit.[17]

Ecology and interactions

Common pests of this plant include various aphids, mites, and leafhoppers, the cotton cushiony scale (Icerya purchasi), and root-knot nematodes (Meloidogyne spp.).[11] It can be attacked by the pit-making pittosporum scale (Planchonia arabidis).[18] It is vulnerable to the fungal plant pathogen Erythricium salmonicolor, which causes galls and the dieback disease known as pink limb blight.[11]

The pathogenic plant fungus Rhizoctonia solani forms white, web-like basidial fructifications on the lower sides of infected leaves of Pittosporum tobira.[19]

The fruit of the plant are not poisonous but not edible. However, they are eaten by bulbuls and other birds in Japan. The sticky substance around the seeds allow them to stick to the beaks of birds and be carried long distances. The stench given off when broken is thought to have evolved to repel predation from foraging animals but it is a favorite of the silka deer.[20][21]

  • Japanese Cheesewood flowers
  • Pittosporum tobira - MHNT
  • Fruits and seeds in Japan
  • P. tobira growing in Italy

References
  1. "USDA GRIN Taxonomy". Retrieved 3 May 2016.
  2. "Japanese Cheesewood". Flower Databse. Retrieved 31 Jan 2021.
  3. RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 978-1405332965.
  4. "Pittosporum tobira in Flora of China @ efloras.org". Flora of China. Retrieved 31 Jan 2021.
  5. Chen; Yang; Lin; Lu; Li; Sun (25 June 2016). "Tree of life for the genera of Chinese vascular plants". Journal of Systematics and Evolution. 54 (4): 277–306. doi:10.1111/jse.12219.
  6. "Pittosporum". Phylogeny of New Zealand Plants. Retrieved 31 Jan 2021.
  7. Harrison, Lorraine (2012). RHS Latin for gardeners. United Kingdom: Mitchell Beazley. p. 224. ISBN 9781845337315.
  8. 日本の樹木　続.
  9. Rjeibi; Ncib; Saad; Souid (30 October 2017). "Evaluation of nutritional values, phenolic profile, aroma compounds and biological properties of Pittosporum tobira seeds". Lipids in Health and Disease. 16.
  10. Gyung-Ja (2006). "In Vivo Antifungal Activities of 67 Plant Fruit Extracts Against Six Plant Pathogenic Fungi" (PDF). Journal of Microbiology and Biotechnology. 16 (3): 491–495.
  11. Stamps, R. H. Tobira Production and Use
  12. Toscano; Scuderi; Giuffrida; Romano (23 Oct 2014). "Responses of Mediterranean ornamental shrubs to drought stress and recovery". Scientia Horticulturae. 178: 145–153. doi:10.1016/J.SCIENTA.2014.08.014.
  13. Ganteaume; Jappiot; Lampin; Guijarro; Hernando (14 Jun 2013). "Flammability of Some Ornamental Species in Wildland–Urban Interfaces in Southeastern France: Laboratory Assessment at Particle Level". Environmental Management. 52: 467–480.
  14. Garcia-Garcia; Sánchez-Medinab; Alfonso-Corzob; Garciab (2016). "An index to identify suitable species in urban green areas". Urban Forestry & Urban Greening. 16: 43–49.
  15. "RHS Plant Selector - Pittosporum tobira". Retrieved 27 May 2013.
  16. "RHS Plant Selector - Pittosporum tobira 'Variegatum'". Retrieved 27 May 2013.
  17. "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 79. Retrieved 2 May 2018.
  18. UC Davis IPM
  19. Tu; Roberts; Kimbrough (1969). "Hyphal Fusion, Nuclear Condition, And Perfect Stages of Three Species of Rhizoctonia". Mycologia. 61 (4): 775–783.
  20. "トベラとはどんな花？特徴的な匂いにまつわる風習と隠語". Retrieved 31 Jan 2021.
  21. "トベラとは？特徴的な匂いをもつ植物の正体と育て方をご紹介！". Retrieved 31 Jan 2021.
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