2 - Plant Anatomy and Morphology

Flowering plants are divided into two groups: monocots (Liliopsida) and dicots (Magnoliopsida) (Grabowski, 2015) (University of California Museum of Paleontology, 1995). The olive tree is a dicot plant, which means that it has got two cotyledons (two “baby” seed leaves produced by the embryo) (Caltech Alumni Association, N.D.) (University of California Museum of Paleontology, 1995). However, dicots and monocots plants do not only differ in the number of cotyledons they contain within the seed, but also in the anatomy and morphology. This week’s weblog we are looking into the anatomy and morphology of a dicot plant, but also into the root system, growth habit and the flowering and seed forming of olive.

Anatomy is said to “the study of the internal tissues and cells of plants”, the study of the arrange of the plant tissue – How the plant is put together (Moncada, Introduction to Agronomy, 2012) (Roger Watts, 2017).

I personally believe that there are no differences when it comes to plant tissue and whether this differentiate between dicots and monocots. This is since plants consist of three plant tissue system; the ground tissue, which is basically the skeleton of the plant – vascular tissue, is the distributor of substances in a plant – dermal tissue, which covers all primary plant part (Brundage, 2001).

Figure I – Stem differences between monocots and dicots (Difference BTW, 2016)

Morphology “deals with the form and structure of plants”, the form and the function – What they do? – How they grow? – How they develop?  (Moncada, Introduction to Agronomy, 2012) (Roger Watts, 2017).

Apart from having two cotyledons, instead of one, there is also a difference in the floweral structure, the leaves, pollen grains and the stem’s vascular bundle. The floral structure in dicots have got four or five parts, which distingue them from the monocot’s three parts pattern. Another charateristic is in the leaves, parallel leaf veins in monocots and netlike leaf veins in dicots plants. Moreover, as crops grow  pollen grains in monocots will have one pore or furruw, while that is dicots three.

Lastly, the vascular bundles in both crop group are arranged differently, since in dicots they are organised in a ring and in monocots throughout the stem’s ground tissues – See figure I. This arrangements mainly have to do in how the plant grows and how they develop (Watts, 2017). Since the vascular tissues in dicots are organised in a ring, the stems can grow in diameter by each time adding new layers of xylem and phoem to the ring. This makes it able for dicot’s plant to add strenght during their secondary growth, which allows them to grow large (Hippo Campus, N.D.).

What do you think are the most interesting morphological characteristics of your crop?

I personally think that the most interesting morphological characteristics of dicot plants is the fact that they are able to add new strength while growing. This is just another reason why plants are absolutely amazing.

The root system of olive tree

One would have thought that since the olive tree is a dicot plant that it also would have a taproot root system. On the contrary, the tree has got a fibrous root system, as it does not have a dominant primary root, but instead has got many secondary roots of similar sizes (Everything maths, N.D.) (Therios, Olives, 2009). Since the tree has got many roots, it is able to reach a larger surface area and therefore increase its access to water and minerals. Moreover, because of the tangled network of root hairs the tree is hold firmly in the soil (Csanyi, N.D.) (Moncada, 2012) (Hippo Campus, N.D.). Unfortunately, the plant is not able to obtain water and nutrients in deeper soil layers, which makes the crop more vulnerable during drought (New Mexico State University, N.D.).

The growth habit

A plant’s growth can be determinate or indeterminate. A crop with a determinate growth habit will grow, breakdown its tissues and then die (radish and tomato), “growth of only a single annual flush of growth” (Utrecht University, N.D.). While a plant with an indeterminate growth habit will also grow but instead of dying, it remain active for years (Biology-Online, 2005), “continuous leaf and shoot growth throughout the growing season” (Utrecht University, N.D.).

The slow growth rate and its height are the olive trees most important characteristics, as they require many years for full fruit bearing (Therios, 2009). Therefore, the olive tree has got an indeterminate growth habit, as it is a long-lived crop, with a life expectancy of 500 years (whereby some have reached the age of 1000 (Dhakal, 1999)) (California Rare Fruit Growers, Inc., 1997). Additionally, the tree is able to sprout back after it has been chopped to the ground, ready to regrow and produce more olives.

It is crucial to understand whether a crop has got a determinate or an indeterminate growth habit, since this influences the harvest method (Moncada, Introduction to Agronomy, 2012). When harvesting olives it is crucial to handle them with care, as they bruise easily (California Rare Fruit Growers, Inc., 1997). However, apart from being careful in order to reduce the amount of bruises. I personally also think that the growth habit influences the harvest method since the grower need to take into account to not cause too much damage to the tree, as this might influence future growth and fruit production of the crop. Simply because there is no point in “cutting off” the tree if it is able to produce for many years.

EXTRA: It is important to give an olive tree a properly prune, since this is said to both regulates the crop’s production and gives tree shape that makes harvesting much eassier (California Rare Fruit Growers, Inc., 1997).

Figure II: Stages of olive flower development (Fiammetta Alagna, 2016)

Flowering

The flowers of the olive forms in spring, which are than pollinated by insects. There are two types of flowers of which the hermaphroditic (perfect flowers – the ability to form a fruit) both contains the male (stamen) and female (pistil) reproductive parts and the unisexual (imperfect flowers) flowers only contain the male reproductive parts (Arkive, N.D.) (Rapoport, 2014). The flowers are said to grow in clusters at the base of the leaves, where the leaf and stem meet. Along the central axis the flowers are grouped, whereby the number of flowers is determined by the number of inflorescences and the number of flowers per inflorescence. The inflorescene (is the group of cluster of flowers that are arranged on a stem (Wikipedia, 2017)) is said to differentiate from axillary buds which were formed the previous year along with new shoot and leaf growth (Rapoport, 2014). Each cluster approximately contains between 15 and 30 fragrant flowers, which are white to yellowish-white.

An olive fruit develops from a fertilized ovary of the olive flower, whereby the production of fruit is directly set upon flower formation and followed with fertilisation (Rapoport, 2014).

In figure I, one can see the different stages of olive flower development.

Seed forming

It has been said that between the embryo and seed coat that there is a small amount of endosperm that is rich in starch, proteins and oil (Hava F. Rapoport, 2016). The multicellular endosperm is formed after fertilization and the rapid growth begins, which is accompanied by the expansion of the ovule. After around 3-4 weeks a single-celled pro-embryo, the one connected to a long filamentous suspensor, will appear at the tip of the new endosperm-filled embryo sac. Then after two months two cotyledons are formed. At 4-5 months a matured olive embryo will contain a root apex at the tip of a short embryo axis. Furthermore, at maturity some olive fruits might contain empty pits with no seed present (Hava F. Rapoport, 2016).

References

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Biology-Online. (2005, August 16). Growth and Plant Hormones. Retrieved September 15, 2017, from Biology-Online: http://www.biology-online.org/11/10_growth_and_plant_hormones.htm

Brundage, R. (2001). Lecture 6: Part 2 - Plant Tissues. Retrieved September 16, 2017, from West Virginia University: http://www.as.wvu.edu/~rbrundage/lecture6b.html

California Rare Fruit Growers, Inc. (1997). OLIVE Olea europaea L. Retrieved September 15, 2017, from California Rare Fruit Growers, Inc.: https://www.crfg.org/pubs/ff/olive.html

Caltech Alumni Association. (N.D.). Vascular Plant Families. Retrieved September 12, 2017, from Caltech Alumni Association: http://alumnus.caltech.edu/~hollin/botany/families/families.html

Csanyi, C. (N.D.). The Advantages of the Fibrous Root & Taproot Systems. Retrieved September 13, 2017, from SFGate: http://homeguides.sfgate.com/advantages-fibrous-root-taproot-systems-104165.html

Dhakal, P. B. (1999). Prospects for Olive Growing in Nepal. Retrieved September 15, 2017, from Food and Agriculture Organization of the United Nations: http://www.fao.org/3/a-af106e.pdf

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Everything maths. (N.D.). Anatomy of dicotyledonous plants. Retrieved September 13, 2017, from Everything maths: https://m.everythingmaths.co.za/science/lifesciences/grade-10/05-support-and-transport-systems-in-plants/05-support-and-transport-systems-in-plants-02.cnxmlplus

Fiammetta Alagna, M. C. (2016, April). Transcript analysis and regulative events during flower development in olive (Olea europaea L.). Retrieved September 15, 2017, from ResearchGate: https://www.researchgate.net/publication/299636051_Transcript_analysis_and_regulative_events_during_flower_development_in_olive_Olea_europaea_L

Grabowski, J. (2015, January). Dicot or Monocot? How to Tell the Difference. Retrieved September 12, 2017, from USDA - Natural Resources Conservation Service: https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/flpmctn12686.pdf

Hava F. Rapoport, A. F. (2016). Olive Biology. Retrieved September 16, 2017, from Springer: http://www.springer.com/978-3-319-48886-8

Hippo Campus. (N.D.). Monocots and dicots. Retrieved September 16, 2017, from Hippo Campus: http://www.hippocampus.org/homework-help/Biology/Kingdom%20Plantae%20_Monocots%20and%20Dicots.html

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Moncada, C. C. (2012). Introduction to Agronomy. DELMAR Cengage Learning. Retrieved September 13, 2017

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New Mexico State University. (N.D.). Chapter 5, Lecture 8 Roots. Retrieved September 16, 2017, from New Mexico State University: web.nmsu.edu/~plsc100/Chapter 5 lecture 8 roots.ppt

Rapoport, H. F. (2014, October). The reproductive biology of the olive tree and its relationship to extreme environmental conditions. International Society for Horticultural Science. Retrieved September 15, 2017, from https://www.researchgate.net/publication/284808873_The_reproductive_biology_of_the_olive_tree_and_its_relationship_to_extreme_environmental_conditions

Roger Watts. (2017). Plant Anatomy and Morphology. Retrieved September 16, 2017, from Blackboard: https://hao.blackboard.nl/bbcswebdav/pid-772059-dt-content-rid-3443653_2/courses/hdb_v_IF2424_1718/Lecture%202%20Plant%20Anatomy%20and%20Morphology2015_16.pdf

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Therios, I. (2009). Olives. CAB International. Retrieved September 16, 2017

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Wikipedia. (2017, April 23). Inflorescence. Retrieved September 15, 2017, from Wikipedia: https://en.wikipedia.org/wiki/Inflorescence

Wikipedia. (2017, August 26). Taproot. Retrieved September 13, 2017, from Wikipedia: https://en.wikipedia.org/wiki/Taproot