Dodder – A Parasitic Plant

On February 9, 2023February 9, 2023 By Bernadette SimpsonIn Plants3 Comments

The Cuscuta genus is the only parasitic genus in the Convolvulaceae, otherwise known as the bindweed or morning glory, family of plants. And Cuscuta species, commonly known as dodders, are the most well-known and widely spread example of stem holoparasitic plants. That’s right, these plants are obligate parasites. They do not contain chlorophyll and cannot, therefore, photosynthesize to make their own food. They must acquire the needed nutrients and water from their host plants.

Folk names, in English, for plants in this genus include wizard’s net, devil’s ringlet, strangleweed, and witch’s hair, to name just a few. I love the imagery of these terms! And once you’ve seen this plant in action, you realize these are great descriptions of these plants that climb, scramble over, and entwine themselves on their host plants with their slender, thread-like stems.

And it is from these many stems that grow haustoria, specialized tube-like growths that insert themselves into the vascular system of the host plants. This allows the dodder to absorb nutrients and water, and therefore grow and attach itself to multiple plants.

“Lab 7 4f) Cuscuta haustoria on host stem xs” by Botanical Voyeur is licensed under CC BY-NC-SA 2.0.

Because the plant does not photosynthesize, there is not much need for leaves, and so the leaves on dodder are very tiny scales. The stems range in color from reddish to yellowish. The small flowers are white, yellow, or cream colored and always hermaphrodites. The stems coil in a counter-clockwise direction.

The parasitic dodder seedlings can germinate and sprout but need to find a host plant quickly, usually within 5 – 10 days, or they will die. They have therefore adapted to use chemosensory, or an ability to sense chemical signals, to grow towards nearby plants. Until they are able to reach a host plant to parasitize, they rely on the food stored in the seed.

Dodder is parasitic on dwarf shrubs, herbs, and grasses and prefers soil with low salinity. We came across dodder in the small oasis of Um Saida (pictured below), near Wadi Kid. The dodder was growing across shrubs of Fagonia sp. as well as herbs such as wild mustard, or jahag (Diplotaxis acris). The dodder was tangled and growing over many plants, clearly illustrating how this could become a problem if the plants parasitize agricultural crops.

There are three species of dodder found in Sinai: Cuscuta palaestina (Palestinian Dodder), C. planiflora (Flat-flowered or Small-Seeded Alfafa Dodder), and C. campestris (Field Dodder). Although Cuscuta species have a rich history of traditional uses in folk medicine around the world, I came across no recorded uses in Sinai in any of the research I was able to access. I am curious to speak with more Bedouin who are familiar with the dodder growing in Sinai.

Pearl Plant

On April 21, 2022April 21, 2022 By Bernadette SimpsonIn PlantsLeave a comment

The distinctive yellow flower stalks and the pearl-like fruit of this desert shrub make it easy to recognize and remember. The pearl plant (Ochradenus baccatus) is quite common in the region and are spotted often on my wanders in the wadis near Dahab. In the springtime, they are buzzing with flying insects – bees, wasps, flies, hover flies, beetles, and more I’m sure. This shrub has been reported as one of the most important food sources for many animal species.

There’s one species in particular that the plant has a special relationship with – the Egyptian spiny mouse (Acomys cahirinus). The fruit – a fleshy, juicy berry – is attractive to desert animals. But when an enzyme in the flesh of the berries combines with what’s inside the seed, it creates a toxic “mustard oil bomb”, deterring most animals from munching on this fruit (and destroying the seeds in the process). The spiny mouse has adapted to this, however. They will collect fruits and bring them to a different, rocky area, one that is safer for them. There, the mice chew and eat the flesh, careful not to bite the seed which they then spit out, avoiding any nastiness and helping to disperse the plant’s seeds. One study suggests these safer places the mice choose are actually “the best places for young O. baccatus plants to germinate, grow and survive.” How’s that for some symbiotic behavior!

The Bedouin of Sinai have also found benefits of the pearl plant, using it in traditional medicine to cure joint pain. A bowl of water in which the leaves have been boiled is placed in a hole in the ground above which a makeshift tent is constructed. The patient then lies beneath its cover for 24 hours. Pearl plant is also used to cure aches and pains in a camel’s body except instead of boiling the leaves, the plant is placed on embers in a hole. In Saudi Arabia, the plant is used to lower blood cholesterol and to counteract malaria.

Recently, a friend and fellow plant-lover asked me if this species had separate male and female plants as she had noticed that some plants were full of berries, while others only had a few. In dioecious plants, only the plants that grow female flowers produce fruit. Date palms are a good example. It turns out, though, that the pearl plant is gynodioecious, meaning that some plants have only female flowers and some plants are bisexual, having both male and female flowers. This explains the phenomenon my friend noticed – two plants, side by side, both in full bloom but only one seeming to fruit fully.

I’ve always liked this plant’s Latin name, Ochradenus baccatus. Ochradenus comes from the Greek for “pale yellow” or “yellow ochre”, and baccatus means “adorned with berries”. It is also known as taily weed and shrubby or sweet mignonette in English and is called gurdhi by the Bedouin in South Sinai.

References:

Bailey, C., & Danin, A. (1981). Bedouin plant utilization in the Sinai and the Negev. Economic Botany, 35(2), 145–162.

K.C. Burns. Seed Dispersal: The Blind Bomb Maker. Current Biology, Volume 22 (Issue 13), 2012, Pages R535-R537. https://doi.org/10.1016/j.cub.2012.05.014.

Ashwagandha

On January 7, 2022 By Bernadette SimpsonIn Plants4 Comments

I had already published the third edition of Wandering through Wadis when, last April, we came across several plants in Wadi Kid that we’d never seen before in the wild. Ashwagandha was one of them.

Ashwagandha is a well-known plant and is one of many names given to Withania somnifera, which grows here in Sinai. There is a related species that is also native to the area – Withania obtusifolia. To complicate matters a bit, there seems to be have been some debate recently as to whether W. obtusifolia should be classified as a subspecies of W. somnifera. Which exact species I have photographed here is a mystery to me, but let’s learn about ashwagandha.

Withania is a genus of plants in the nightshade family. Of the 23 species, two – including W. somnifera – are considered economically important and are cultivated in various regions around the world for medicinal uses. In Ayurveda medicine, ashwagandha is used as a medicinal herb and dietary supplement. Other names for W. somnifera include Indian ginseng, poison gooseberry, and winter cherry…but I’ll stick to using ashwagandha (until I can confirm the Arabic name).

Ashwagandha is a drought-tolerant evergreen shrub that grows in dry, stony soil and can grow to be between 35 and 75 cm tall. The branches are hairy and grow out radially from the central stem. The leaves are dull green, generally egg-shaped, and 10 – 12 cm long. The flowers are small, green, bell-shaped and grow in clusters; the ripe fruit is orange-red.

Sadly, a 2020 article in the Egyptian Journal of Botany reports that of the 8 threats the authors categorized plants as facing, Withania somnifera is subject to seven: over-collecting; habitat loss; clearance for agriculture, mining and quarrying; disturbance by cars and trampling; urbanization; tourism; and climatic change and environmental conditions. Even though ashwagandha is apparently a common plant in Egypt, after reading that list of threats, I feel lucky to have come across these plants in the wild. I had seen them before as my husband had them growing in his permaculture garden. He tells me that ashwagandha seems popular with Egyptian gardeners and farmers these days. Have you come across ashwagandha in your wadi wanderings? Or have it growing in your garden?

Leaf Morphology: Arrangement

On September 26, 2021 By Bernadette SimpsonIn PlantsLeave a comment

Since my guidebook was intended for nature-lovers, not necessarily plant specialists, I took care to define and explain the technical terms used in the descriptions of the plants in my book, choosing simpler English synonyms when possible. But it’s not always possible. So I thought it might be helpful to dedicate a few blog posts to delving into some of these technical terms a bit more, deepening our understanding and looking at some specific examples from our desert plants. And I thought I’d start with the terms used in leaf morphology.

In botany, morphology is the study of the size, shape, and structure of plants. Plant biologists use these characteristics for the descriptions, classification, and identification of plants. Having some understanding of these different characteristics will help you to recognize and identify the plants you see while wandering through wadis.

In leaf morphology, one of the key characters studied is leaf arrangement, the number and placement of leaves along the stems. This arrangement of leaves is called phyllotaxy and we’ll talk today about four general categories – alternate, opposite, whorled, and rosette – although there are various levels and ways of categorizing these patterns.

A node is the point where the leaf emerges from a stem or twig, and arrangement is always regular.

In the alternate pattern, sometimes called spiral, each leaf or leaflet grows from a different node.

In the opposite arrangement, two leaves or leaflets grow per node, on opposite sides of the stem.

If, in this opposite pattern, the successive leaf pairs grow at right angles, it is called decussate. These perpendicular pairs of leaves are typical of plants in the mint (Lamiaceae) family, like the ones pictured below.

In the whorled arrangement, three or more leaves or leaflets are connected at one node. Blepharis attentuata, pictured below, grows whorls of four leaves.

When the leaves of the plant emerge from the base in a whorled arrangement, spreading out in a circle, it is called a rosette.

Understanding the various patterns of leaf arrangement will help you to understand plant descriptions that you read in my book and other sources. And if you come across a plant you do not know, take note of its leaf arrangement (Photos are a great way to document this.) because it could be an important characteristic to consider when identifying the plant. In the next few posts, we’ll learn about other key characters in leaf morphology that will help us identify the plants.

One of my favorite desert plants is the caper bush; its leaves grow in an alternate pattern. I also love germander (Teucrium sp), both for its delicious fragrance and its neat geometrical leaf pattern. Do you recognize these leaf patterns in any of your favorite desert plants?

Scarce Marsh Helleborine

On March 23, 2021March 24, 2021 By Bernadette SimpsonIn PlantsLeave a comment

If you follow the Wandering through Wadis Facebook page, you might recall the photographs of orchids that I shared a few weeks ago. I had no idea that there were orchids growing in the desert, but after my friend sent me photos of the blooms she had seen, I obviously had no choice but to go see them for myself.

I had identified the orchids in my friend’s photos as Scarce (or Eastern) Marsh Helliborine (Epipactis veratrifolia) but, admittedly, I knew nothing about orchids. So I’ve been reading up on them. And I’ve learned a lot of fascinating things about orchids in general, but also about these rare beauties that are native to Sinai. (They are not found in mainland Egypt.)

Most orchids (more than 99% of all species) are epiphytic and use their roots to attach themselves to and grow on trees. The Scarce Marsh Helleborine, however, is a terrestrial, or ground, orchid and grows its roots firmly in soil.

This helleborine is a perennial herb and grows, from a fleshy rhizome, to be between 25 – 150 cm tall. The leaves are ovate (egg-shaped) and pointed at both ends. They grow along the stem and can be 8 – 25 cm long. The inflorescence, or cluster of flowers, grows atop an erect stem. The flowers are fairly open and are green to yellowish-green in color with purplish or reddish radial stripes. The lip, or bottom middle petal, is tipped in white. The upper part of the stems, bracts, ovaries, and sepals are covered in short, fine hairs. In Dahab, the orchids were found growing among native grasses in a wet area.

Like all orchids, this helleborine is dependent on a mycorrhizal symbiosis, a mutually beneficial relationship between a plant and a fungus, to complete its life cycle. The plant’s fruit capsule is full of microscopic seeds (in some species, over a million), but these seeds all lack endosperm. Endosperm is the tissue usually found inside seeds that provides nutrition to the plant as it sprouts. Because an orchid’s seeds don’t have this inborn nutrition, they rely on fungi to provide them with the nutrients they need to germinate. The chance of germination is so small that only a minute fraction of the released seeds grow into adult plants.

But before a plant can even produce any of these seeds, it must first be pollinated. And to help ensure that, the Scarce Marsh Helleborine employs a trick, a special mimicry, to lure pollinating hoverflies to its flowers. The flowers emit three chemical substances that are usually released as alarm pheromones among aphids. Aphids are the preferred diet of hoverfly larvae. So female hoverflies smell these chemicals, interpret this to mean that aphids are nearby, and proceed to lay their eggs near the source of the scent – the flowers. The hoverflies are rewarded with a small sip of nectar, but their larvae are doomed to starve because, when they hatch, there will be no aphids around to consume. (This is a strange contradiction from an evolutionary perspective because since the larvae die, the number of potential pollinators decreases.) The orchids are mimicking the aphids, taking advantage of the female hoverflies and deceiving them into pollinating the flowers.

As you can see, these rare orchid blooms are not only beautiful but also full of amazing natural wonder!

Resources:

Plants of the World Online (Epipactis veratrifolia)

Orchid tricks hoverflies (Max Planck Society)

Desert Plant Adaptations (IV) ~ Leaf Adaptations

On February 20, 2021 By Bernadette SimpsonIn PlantsLeave a comment

Getting back to my series on desert plant adaptations, let’s discuss some of the ways that leaves have adapted to help plants survive the hot and dry conditions of the desert wadis.

Besides dropping all of their leaves like drought-deciduous plants, some plants simply have smaller or fewer leaves. Smaller leaves means there is less surface area open to the wind and sun, and so less water is lost through transpiration. Semi-shrubs and shrubs may have large leaves in the winter that are shed during the dry season and are replaced with smaller leaves in the summer. Artemisia herba-alba and Phlomis aurea both have smaller summer leaves.

Another strategy that helps conserve water is folding or rolling up the leaves so that the stomata are facing inwards, reducing the surface area subject to transpiration. This adaptation is employed by Helianthemum species, Fumana thymifolia, and many perennial grasses.

But it’s not just transpiration that leads to water loss. Leaves also lose water through their cell walls. To combat this, the leaves of some desert plants have a waxy coating or a thick cuticle, the film covering the surface, which helps seal in and protect moisture already in the leaves. Most xerophytes have a thick cuticle.

Hair on the leaves and stems also helps reduce water loss by providing shade and trapping water vapor near the plant’s surface. Artemisia herba-alba, Phlomis spp., Majorana syriaca, and other plants utilize this adaptation.

Plants needs energy from the sun to photosynthesize. What energy they don’t use to make food is used to heat the leaf up. That is very useful for plants growing in cold climates whose leaves need to be a bit warmer to photosynthesize but not so necessary for desert plants, which must reflect some of this solar radiation or risk over-heating. How do they do this? Some plants, like Capparis sinaica, have a waxy coating on their summer leaves which gives them a lighter – and more reflective – color than their winter leaves.

Leaves of Atriplex species also have a different color depending on the season, but they don’t use a waxy coat. Instead, the leaves are covered in vesicular hairs that contain a salty solution. In the winter, the hairs are full and transparent, allowing more absorption of the sun’s energy. In the summer, the water evaporates and the hairs dry out causing the leaves to be a lighter color that reflects the sun’s rays.

You can read more about each of the species photographed above in my book. In the next post in this series, we’ll learn about stem adaptations. Stay tuned!

Desert Plant Adaptations (III) ~ Drought-escaping Plants

On October 1, 2020 By Bernadette SimpsonIn PlantsLeave a comment

I’ve written about two general strategies that plants employ to survive in desert habitats – succulence and drought-deciduousness. Today I’ll introduce the most successful adapters to life in the desert – drought-escaping plants. Plants escape drought in one of two ways. They either survive only as seeds or they use taproots.

Annuals are plants that wither and die during the dry seasons but not before completing their life cycle, sometimes in just a few weeks. Their seeds are covered by a thick protective coat and are dispersed, only to wait underground as part of the desert’s “seed bank”. Contained within their seed coats are certain chemicals that prohibit germination. The seeds must wait for rain to wash these chemicals away before they can sprout. These are the plants that amaze us here in Sinai when our desert sands are suddenly covered in green after a spring rainstorm. These are also the plants that are so important to the Bedouins’ herds of goats and sheep. Some of these annuals that survive dry seasons as seeds include Astragalus spp., Artemisia spp., Diplotaxis spp., and Tribulus spp. and are pictured below.

Using taproots is also a successful strategy to avoid the problems associated with drought. A taproot is a very thick and long root that grows directly downward. Think of a carrot. The taproot is the main central root which other smaller roots grow off of. The long taproot allows the plant to reach water stored deep underground, providing an almost constant source of water. The taproots of Convolvulus lanatus, pictured below, and Artemisia monosperma are also covered with a thick bark that helps the roots to withstand the withering caused by wind.

You can learn more about these desert plants in my book, Wandering through Wadis: A nature-lover’s guide to the flora of South Sinai.

Desert Plant Adaptations (II) ~ Drought-deciduous Plants

On September 4, 2020 By Bernadette SimpsonIn Plants2 Comments

It’s been longer than I had planned, and I’m not sure where the time went (well, a lot of it went to waiting for a new computer when my old one bit the dust), but I’m finally back with more information about how the plants in South Sinai have adapted to survive the harsh desert conditions! In the first installment of this series, I talked about succulence, the ability of plants to store water in their leaves, stems, and/or roots.

Today, I’ll discuss drought-deciduous plants. Instead of storing water like succulents, these plants use a different method to deal with drought conditions. During the dry seasons, they drop their leaves, allowing them to save water that would otherwise be lost during transpiration (similar to sweating in humans).

Because these plants don’t have their leaves to make food in the summer, their stems take over the photosynthesis process. (More on this in a future post.) Drought-deciduous plants also slow down their metabolism, making only enough energy to keep the plant alive. This means when conditions for growth are favorable again, the plants don’t have to start from zero. They’re already idling and ready to go, if we think in car terms; they don’t have to turn the ignition on first.

Lycium shawii, or Desert Thorn, is one example of a plant that is completely leafless in the summer. (It also has succulent leaves, so more than one adaptation to help it survive.) And because I don’t hike in the summertime, I don’t have photographs of this plant without leaves. But here’s a pic of their beautiful lush leaves:

In my next post, I’ll discuss the most successful adapters to life in the desert – the drought-escaping plants – so be sure to follow the blog or the Facebook page so you don’t miss out!

Desert Plant Adaptations (I) ~ Succulence

On June 17, 2020 By Bernadette SimpsonIn Plants4 Comments

Plants that have adapted to living in dry habitats are called xerophytes, and they are the characteristic plants of deserts and semi-deserts. Over the next few weeks, I’ll be explaining some of the adaptations that allow them to survive in such a harsh desert environment. And it is harsh! Besides the limited supply of water, these plants must also survive high daytime temperatures, high levels of solar radiation, high levels of salinity, and strong winds. Water, however, is the most important ingredient in their lives and they must prevent water loss and overheating to survive. In general, to overcome these obstacles, desert plants can be classified into three main groups according to how they deal with the drought conditions – succulence, drought-deciduous, and drought-escaping. Today, I’ll talk about succulence.

Succulence is the ability of plants to store water in their leaves, stems, and/or roots. Cacti are a classic example. Succulent plants have shallow roots, allowing them to quickly absorb any available moisture, including dew. These plants can begin to grow 24 – 48 hours after rain. You may have noticed that there aren’t many cacti growing in the wadis of South Sinai, but there several species of succulents.

Species with Succulent Leaves

If you think back to your high school biology class, you’ll recall that photosynthesis is the process that allows plants to use the sun’s energy to convert carbon dioxide (CO₂) and water into sugar. Basically, it’s how plants make their food. There are pores, called stomata, on the leaves that open and close to absorb carbon dioxide from the air and release oxygen. When these stomata open and close, water vapor is also released and evaporated. This release of water is called transpiration. It’s similar to sweating in humans and can help cool the plant. And we know that if we sweat a lot, we should drink more water to stay hydrated. However, desert plants do not receive a lot of rain to replace this lost water. So they have adapted to conserve as much water as possible.

Species with Succulent Stems

One way succulents do this is to use a different type of photosynthesis, one that allows the plants to make food without losing a lot of water to transpiration. It’s called crassulacean acid metabolism, or CAM photosynthesis. Plants that use CAM open their stomata at night when temperatures are cooler and keep them closed during the day. Instead of using sunlight to convert the CO₂ to food right away, plants store the CO₂ they absorbed at night as crassulacean acid. As the day begins and the temperature starts to rise, the acid is changed back into carbon dioxide and then used in photosynthesis. This allows the plants to conserve water and use it to make food instead of losing it to evaporation.

Species with Succulent Stems and Leaves

That’s a pretty fascinating adaptation, isn’t it? But it’s only the start! Stay tuned for my next post where I’ll discuss drought-deciduous and drought-escaping plants.

Stagshorn Lavender

On February 18, 2020 By Bernadette SimpsonIn PlantsLeave a comment

Many people are surprised to learn that lavender grows in the desert wadis of South Sinai.

Stagshorn Lavender (Lavandula coronopifolia) is one of 47 lavender species in the Lavandula genus and one of two that are native to Sinai. While not as fragrant as its cousins, the leaves of Stagshorn Lavender do have a pleasant scent and are edible, grazed by the local herds of goats, sheep, and camels.

And I can attest to their tastiness! When I had a plant growing in my desert garden, we often added the leaves to our salads.

It is in fact their distinctively branched stems that gave this species its common name – stagshorn. In Arabic, this plant is known as zeiti, diktae, or netash.

Stagshorn Lavender is a small shrub in the mint family and can grow up to one meter in height. Lavandula coronopifolia grows in open rocky habitats, desert plains, and foothills and is the most widespread species of lavender across northern Africa.

The flowers are sky blue to lilac in color and bloom between January and April.

Which means you can seem them in bloom right now! When I was wandering through wadis last weekend, the lavender plants were one of the few plants with flowers. There would be more if the area had received more rain this season, so my fingers are crossed that the small chance of rain forecast for tomorrow comes through!