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•Key points :

•Rainfall is low

•Water resources may be deep in the ground

•Temperature are high during the day

•High temperature increase transpiration.
the soil is salty !

Find some examples of adaptation of Xerophyte and halophyte
and write about their structure and adaptation to a particular condition  (one example of each)

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Xerophytes And Halophytes

1. Xerophytes

An example of a xerophyte is a cactus. Cacti respond to little rain by having the ability to store water. Cacti respond to high temperature by having little leaves to minimize transpiration and minimize their water needs, and they transpire at night when it is cooler. Cacti also adapt to not transpiring during the day by performing a special type of photosynthesis by acid created carbon dioxide, which leaves them with no need to external carbon dioxide. Finally, cacti respond to deep water sources by having long roots. Other types of xerophytes adapt to conditions by having g a short lifespan right after rain fall.

1. Halophytes

An example of a halophyte would be New Zealand spinach and this plant doesn’t really have to adapt to high temperature, but it has to deal with salty soil, and it adapted to this by having scaly leaves, and shedding leaves when water is salty. Some halophytes store water too. The New Zealand spinach also has a sunken stoma and thick cuticle layer on the leaves to regulate transpiration and water intake so the plant wont over transpire and dry out. Halophytes like this kind of spinach adapt to low rainfall by using salty water from the soil. They also adapt to deep water sources by having longer roots to reach for the water.

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Xerophyte

Xerophyte plants have significant structures that permit their living in dry conditions. Such structures tend to reduce the rate of transpiration. First, the thick wax cuticle that acts a barrier for evaporation and has a shiny surface that decreases temperature and reduce heat. Secondly, xerophytes tend to have a submerged stomata in the epidermis to elongate the diffusion process and decrease evaporation rate.  Thirdly, the spine shaped small leaves that protects xerophytes from animals, sun, and high evaporation rates. Finally, xerophytes have a circular shape root system that absorbs high amount of water when it rains.
ex: pineapple plants.

Hydrophytes

Unlike xerophytes, hydrophytes have structural advances that aids its living in extremely wet conditions and the increase of gaseous exchange. Firstly, the epidermis layer has a minimal presence and the xylem tubes are, in most cases, absent, due to high water concentration. Secondly,  the stomata ,that has a very thick wax cuticle, are found om the upper surface of the leaf and repel water. Thirdly, Aerenchym, which is a plant tissue containing air spaces, presence makes the process of roots gaining o2 from soil unnecessary by diffusing oxygen from aerial portions of the plant to the roots. fourthly, the roots of hydrophytes are reduces and in some cases absent to avoid the over-absorption of water. Finally, the shoot of such plants exist above the surface of water for fast gas exchange.
ex: lilies and lotus.

References:

https://www.britannica.com/science/aerenchyma

https://www.gardeningknowhow.com/ornamental/water-plants/wgen/hydrophytes-information.htm

https://www.thestudentroom.co.uk/revision/biology/xerophytes-and-hydrophytes

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Omar Islam              Xerophytes & Halophytes

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Omar Islam              Xerophytes & Halophytes

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Xerophytes:
S uch plants adapt to environments with an extremely low level of H20 like deserts.

Examples of Xerophytes:
Oleander
Pineapples
Peyote
Barbary Fig
San Pedro Cactus

Adaptations of xerophytes include having thick and fleshy stems or leaves. Other xerophytic adaptations are having waxy leaf coatings, and the ability to drop leaves during dry periods. In addition to the ability to reposition or fold leaves to reducee sunlight absorption, and lastly the development of a dense, hairy leaf covering.

Halophytes:
Halophytes are plants that can tolerate and withstand places that have an extreme amount of salt in the soil. The most common type of Halophytes are Mangroove Trees.

Marshes and Mudflats are such environments where Halophytes can be found.

Examples of Halophytes:
Lavender
Mangrove Trees
Thrift
Sea Lavender
Rice Grass

Halophytes have root cells that have a higher than normal concentration of solutes, which enables them to take up water by osmosis from the surrounding soil.

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Renad Yasser       Xerophytes and halophytes

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Renad Yasser       Xerophytes and halophytes

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Xerophytes and halophytes are plants conditioned to living in very dry habitats or soils and Waters with very high salinity
These plants adapt themselves and modify their structure  an example is having  small leaves or thick waxy cuticle  to retain moisture and cope with the surrounding environment.

Where Xero means dry and Phyte means plant Xerophytes  are plants that have adapted themselves to live and survive in very dry regions and conditions.

EX: Cactus

Since the water loss of xerophytes exceeds their water uptake they have specific features that helps them cope with the environment and balance their water level

Xerophytes have modified Leaf structure and functions to minimize water evaporation and therefore achieve a balanced water intake and loss

Leaves of the xerophytes have a thick waxy cuticle to prevent or minimize water evaporation

Curled leaf:

One of the ways xerophytes used to reduce or prevent transpiration from the stomata is curling the leaf, where the lower epidermis is Protected or trapped from the outside air and therefore creates a moisture region with very low transpiration rate.

Hairs on the lower epidermis the hair is present on the lower epidermis of the leaf traps moisture near the leaf surface reducing the water potential gradient and therefore limiting the loss of water by transpiration.

The sunken stomata on the lower epidermis is sheltered from the air or wind and this helps reducing transpiration.

Instead of having flat wide leaves Xerophytes have small thick ones to help reduce the surface area on which transpiration would take place and therefore reduce The amount of water  lost.

This reduction of the leaves size has to be balanced with the surface area needed for photosynthesis.

Abscisic acid is released to close the stomata at times during the day where transpiration rates are very high.

Halophytes are plants that have adapted to life in very high salinity or salty soils or waters.

EX: Salicornia europaea plant

Unlike plants that live in normal conditions and intake water to roots in agreement with the concentration gradient, halophytes have this gradient oppositely set in where water with more salt is on the outside instead of inside, this would result in water moving from the inside of the plant and into the soil to achieve equilibrium unless the inside of the plant is even more salty or has more solute like (potassium or sugars) than the outside.

Halophytes have  the ability to increase the salts or solute levels inside the plant in order for water to go from the soil and into the roots.

Similar to Xerophytes halophytes have a thick waxy cuticle in order to minimize or prevent the evaporation of water.

Halophytes  grow in a vertical manner so when the sun is right on top of the plant, it will have limited or minimum  surface area directly facing the sun, which again minimizes water evaporation

Halophytes can actively transport extra salts (Na) back into the soil

https://www.youtube.com/watch?v=fRdKrZy7RgA

https://study.com/academy/lesson/xerophytes-definition-adaptation-examples.html

https://www.youtube.com/watch?v=i6QwzTHppmQ

https://study.com/academy/lesson/plant-adaptations-hydrophytes-mesophytes-xerophytes.html

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Carnations and Chrysanthemums Jana Tarek

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Carnations and Chrysanthemums Jana Tarek

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Carnations:

Type of long-day plant

Usually don’t flower during winter and autumn where the night is long

Horticulturalists can manipulate their growth by exposing them to artificial light

Carnations require long night length in order to grow

Chrysanthemums

Type of short- day plant

Usually don’t flower during summer because night length is short

Horticulturalists can manipulate their growth by covering them with an opaque cloth

Chrysanthemums require long day-light exposure in order to grow

References
http://ib.bioninja.com.au/higher-level/topic-9-plant-biology/untitled-3/photoperiodism.html

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I-                    Carnations

1-      Photo periodic or how much exposure to darkness a plant gets, affects carnations’ flowering. Carnations tend to flower in one of 2 ways either by flowing at a normal rate all year long when it’s long day or when the had short darkness period and long day period, while when carnations had a short day or long darkness and short-day light, the started flowering vigorously, but for specific periods only.

2-      Scientists can or gardeners can make use of this by exposing some of the plants to long day and other to short day, so they can have the plant available at all times from the plants that are grown in long day or much light (although it wouldn’t be as much when I come to amounts), and also have vigorously growing carnations in seasons from those that are grown in short exposure to light. Hence gardeners can manipulate photo periodic by either exposing the plant to much lights or not which would allow us as humans to control the seasons in which carnations bloom and the amount that blooms.

II-                  Chrysanthemums

1-      Chrysanthemums is also another plant that is greatly affected by day length. In fact, it may even be more affected than the carnations. While carnations grow in both long day and short day (although at different rates), Chrysanthemums ‘flowering is only initiated by short day. In other words, when the day id short and the plant isn’t getting much light, it starts to flower.

2-      Gardner’s can make use of this to make the plant flower all year. Simply gardeners would plant these plants in darker areas and allow them to get exposed to light for less than 15 hours, which initiates the flowering process in the plant and this means that if those condones were maintained the flowers would bloom all year. To sum up, if gardeners minimize the exposure of light to this plant, they’re going to get it to bloom all year long.

Resources:

URLhttps://garden.org/courseweb/course1/week4/page15.htm

Website TitleLong-day and short-day plants - Garden.org

Article TitleLong-day and short-day plants

Date AccessedOctober 21, 2018

URLhttps://www.cabdirect.org/cabdirect/abstract/19600306526

Website TitleCAB Direct

Article TitleWelcome to CAB Direct

Date AccessedOctober 21, 2018