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The beauty of botany: intriguing plants from my garden

The experience of being in nature is something profoundly sensational with multiple layers to it. Gardening has been my passion from a young age, fostered by my mom who took me to botanic gardens and plant fairs at Chatuchak. For the past 6-5 years, I’ve been a prolific gardener, and, in this article, I’d like to share with you a slice of my garden. I want to showcase three interesting plants along with scientific facts which make them special.

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[Plant display, Queen Sirikit Botanic Garden, Chiang Mai, Thailand]

Begonia leaf propagation: can you grow an entirely new plant from a leaf?

The answer is yes. But for some context, begonias are a family of succulent plants that occur in tropical and subtropical areas.  They contain around six subgroups and over 2,000 species and hybrids. They are known for their asymmetry and striking variegation seen in the picture above.

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The genus Begonia [Begoniaceae], are notable for their ability to propagate with a single leaf cutting, a propagation method widely recognized in scientific literature (Manuela and Carmen, 2013) [1]. Adventitious root growth, the formation of roots in non-root areas, is denoted to be the cause of a stress response.

 

Down to the cellular level, shoots that have developed from a leaf cutting employ the exact same growth process as a fully grown plant. They are growing with mitosis which is the division of cells to produce more tissue. Asexual reproduction is not to be confused to our notion of sexual reproduction in which the gametes of two parents fuse to make a genetically unique offspring: the shoot grown is genetically identical to the parent plant, and in other words, they are clones of the mother plant.

A further explanation: the creation of roots is triggered by Auxin production at the base of the cut (Steffens and Rasmussen, 2015) [2]. Researchers furthered the claim when they demonstrated that an inhibition or decrease in the levels of strigolactones (a group of plant hormones produced by roots) correlates to increased adventitious root production (Rasmussen, 2012) [3]. From then on, a shoot develops and later into a plant.

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In the wild, as little as some moisture along with shade can ensure that a fallen leaf can start new life: this is an ingenious adaptation considering how chaotic the forest habitats are with the shortcomings of rain and traversing animals.

 

Moreover, a study concluded that different species had their ideal propagating methods (Hashim et al, 2016) [4]. However, from various anecdotes of plant-collecting friends and sellers as well as past experiences, I’ve propagated mine using hydroponics, a medium of perlite with a water supply.

 

 

You can produce clones of a plant you like but on top of that, it’s extremely rewarding to grow Begonias because you gain an intuition of the optimal conditions each plant requires. Commonly passed on in the plant community, the ideal condition varies in between each grower. There is no magic formula.

 

As seen below, Begonias come in more than one form. The genus has a rhizomatous and horizontal-growing form, and cane and vertical form. Both forms can vary from a fully green leaf to dotted and covered in variegation; leaf shapes vary too.

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[Left] Begonia hybrid, finger root plant, my home. [Right] Begonia siamensis and various Begonia hybrids, Queen Sirikit Botanical Garden, Chiang Mai, Thailand.

Selaginella: do ancient plants still exist?

In the domain of plants, divergences happened over time. This created plants that differed from each other in characteristics. Of one of these divergences (the divergence of bryophytes), were created the clade of vascular plants (vascularity was a keystone evolutionary step which created lignified cells). Selaginella have already occurred since 440 MYA (Banks 2009) [5], being one of the first vascular plants. In terms of morphology Selaginella, has endured a low degree of selection, and therefore it is a jarring prehistoric representation of plant life, making it a fascinating genus to collect.

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The ancient morphologies include microphyll leaves,

dichotomous branching and the bearing of strobili to

produce spores. Lycophytes, as vascular plants, were

the first plants to produce roots. Former bryophytes

conduct photosynthesis by absorbing water from their surfaces.

 

Put simply, Ferns exist in two cycles. The visible plants

we see are the diploid sporophyte form of Selaginella: they are

parent plants with both sets of chromosomes. When they

become reasonably developed, they then produce haploid

microspores (the male gametophyte) and also haploid megaspores (the female gametophyte): both are vessels which produce respective sex cells which fertilize each other in moist conditions (Cronquist et al. 1972) [6].

[Left] Example of phylogenetic tree for flora. Selaginella diverged from Bryophytes to form Lycophytes (McCarthy et al. 2014).

Selaginella make a good low lying shrub as they trail along the ground. Under optimal conditions they send off rhizomes. Rhizomes are extensions of the plant, a geotropic device that play a role in helping a plant anchor itself to the substrate; roots develop from the Rhizome as it matures.

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[Left] Diagram to show dichotomy.  [Right] diagram to show Selaginella growth habit.

Selaginella appreciate frequent waterings and places to trail. In my experience they have also been pretty resistant to sunlight which is interesting. As seen in the picture above, they make great ground covering. I occasionally run my hands through them— it’s a soft cloud-like sensation.

 

To answer the question, it must be said that all living matter came from somewhere: however, what makes Selaginella special is that they retain the qualities of an ancient ancestor essentially allowing us to experience a touch of prehistory. I saw many along the nature trail in Khao Yai National Park which strongly evoked the existentialist in me: how long has the forest been undisturbed? Pretty long.

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[Top left] Selaginella colony, my home. [Top right] Selaginella diploid sporophyte forming in the moon soon season, on rock face, Khao Yai National park, Saraburi, Thailand. [Bottom left] Selaginella Sp, same location as (Top right). [Bottom right] Selaginella growth habit.

Epiphytes: fascinating free riders.

 

Epiphytes are flora which grow on non-soil surfaces such as tree trunks and

rocks and in some cases they never send roots to the ground. They rely on

rainwater and the diffusion of water vapor from the atmosphere. Importantly,

they are not parasitic to their host: they do not deprive their hosts of

nutrients. To call them free riders would therefore cast a negative connotation

for they are extremely beautiful specimens conversely.

 

How do Epiphytes take in water if they don’t have roots? Osmotic potential is

tendency of water to diffuse into plant material given factors like plant tissue

solute concentration and plant surface area. Interestingly, a study concluded a

conflicting finding: epiphytic species had high osmotic potential (taking in less

water than peers) (Benzing, 1990) [7] (contrary to the idea that they must

seize every opportunity to obtain water). The study suggested that adapting to

a high osmotic potential was unessential given how scarce water is in the first

place: alternatively, having a low osmotic potential results in early turgor loss.

Hence having a high osmotic potential is one of the many adaptations made to conserve water.

 

This was reinforced when five epiphytic individuals from different species was seen to have lower osmotic potential compared to their ground, hemiepiphytic-counterparts (Holbrook and Putz, 1996) [8]— the ground-rooted individuals could engage in transpiration more liberally and accommodate for more water loss given their connection to the ground. 

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[Right to left] (Araceae) Philodendron tripartitum, my home. (Both in Khao Yai National Park, Saraburi, Thailand) Epiphytic orchid and hemiepiphytic Ficus. [former page] (Araceae) Raphidophora hayi.

A journal disputes the current notion that epiphytic plants are nutrient deprived, suggesting that water uptake is the main limitation of growth (Zotz and Hietz, 2001) [9]. Epiphytes in the wild primarily obtain nutrients from dinitrogen fixation and the leaching of their host plant, for example the bark (Benzing, 1990) [7].

 

If a plant’s roots reaches the ground, it is classed as a hemiepiphyte. An example of how this could happen is when a specimen germinates on a branch but sends off roots to obtain water which eventually reaches the ground. With access to water and nutrients, they are much more viable. My epiphytic plants are planted directly in the ground and encouraged to climb up a tree later on.

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As you can see in these photos, Philodendron tripartitum climbs up the tree starting from the ground.

 

Facilitated by skototropism (negative phototropism), they grow head for dark spots like the shadow of a tree. (I usually grow them by the base of a tree anyway to ensure success). Various growth hormones are stimulated on the dark side of the plant gaging it toward the support. They eventually switch to growing with positive phototropism when they climb up a tree.

 

Whey are epiphytes/hemiepiphytes worth growing? They are a superb option to fill up vertical spaces, adding flare to tree trunks. Genera like Philodendron and Anthurium boast unique leaf shapes whilst orchids have lovely blooms. In the spirit of a venturesome gardener, they are yet another category amongst many waiting to be mastered.


 

We learn many terms in biology class like auxin, phototropism and epiphyte but they come, almost always through badly printed 2-D diagrams or through old screencasts from the 2000’s. This turns a blind eye toward the breadth that botany yearns to offer. Being one with my garden has positive effects in terms of mental health, providing a outlet for the stresses of being a student.

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I garden, at the very least, one time per week. However, the habit of walking into my garden has morphed seamlessly into my daily life. I walk past my gardening setup everyday so at the very least I still catch a glance at my small green friends. In this article I’ve spoken about Begonia propagation, Selaginella and Epiphytes. I’ve spoken briefly on the science that makes them unique and also the way to style your garden. I hope that this article would have ignited interest and stimulated some more appreciation for flora among the Patana community.


This project was incredibly fun to research and gather together. I hope to share Scientia more of my work in the future

My garden setup, my home.

Written by Lenny

 

Bibliography

 

Manuela, M. and Carmen, N. (2013).  ‘Study on the vegetative propagation of some Begonia L. Species.’

https://www.researchgate.net/publication/283786298_STUDY_ON_THE_VEGETATIVE_PROPAGATION_OF_SOME_BEGONIA_L_SPECIES

 

Steffens, B. and Rasmussen, A. (2015). ‘The Physiology of Adventitious Roots.’ Marburg, Germany.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734560/

 

Rasmussen, A. (2012). ‘Inhibition of strigolactones promotes adventitious root formation.’ Ghent, Belgium.

https://pubmed.ncbi.nlm.nih.gov/22580687/

 

Hashim, M. (2016). ‘Impact of propagation media and different light levels on vegetative propagation of Beginias’

https://www.researchgate.net/publication/328163815_IMPACT_OF_PROPAGATION_MEDIA_AND_DIFFERENT_LIGHT_LEVELS_ON_VEGETATIVE_PROPAGATION_OF_BEGONIAS

 

Banks, J. (2009). Selaginella and 400 million years of separation. Ann Rev Pl Biol 60: 223-238.

 

Cronquist A, Holmgren AH, Holmgren NH, Reveal JL, Holmgren PK (1972) The vascular Cryptogams and the Gymnosperms. Intermountain flora: vascular plants of the intermountain West, USA. Volume 1. Geological and botanical history of the region, its plant geography and a glossary. New York Botanical Garden, New York

 

Benzing DH, (1990). Vascular epiphytes. General biology and related biota. Cambridge: Cambridge University Press.

 

Zotz, G., & Hietz, P. (2001). The Physiological Ecology of Vascular Epiphytes: Current Knowledge, Open Questions. Journal of Experimental Botany, 52, 2067-2078.

 

Holbrook N, Putz F. (1996). From epiphyte to tree: differences in leaf structure and leaf water relations associated with the transition in growth form in eight species of hemiepiphytes. Plant, Cell and Environment19,631–642.

 

Selaginella diagram: http://premabotany.blogspot.com/2018/12/selaginella-classification-structure-of.html

 

Phylogenetic tree: McCarthy T, (2014). Phylogenetic analysis of pectin-related gene families in Physcomitrellapatens and nine other plant species yields evolutionary insights into cell walls. https://www.researchgate.net/figure/Summary-of-land-plant-phylogenyThe-evolutionary-relationships-of-the-ten-PlantTribes_fig1_261102239