The survival of the fattest: Saving water, part 2 of 2

The outer skin may also be enclosed in a layer of cork or wax; this will make the surfaces  of leaves and stems practically waterproof. It will also  prevent the heating of the leaf, which lowers temperature and thereby the rate of transpiration from the leaf. This is found in many succulents and other xerophytes. Plants can raise the amount of wax when the temperatures are very high or the relative humidity is very low.

The white wax layer of Adromischus leucophyllus also reflects light
The peculiar Othonna herrei is completely covered in wax


Usually the plant’s water is bound in substances that do not release water easily, so that even if the plant is damaged, the inside stays moist for a long time. (Tanquana prismatica).


The bladder cells we met before, do more than storing water. When the plants start suffering from drought stress, the cells collapse and thereby obstruct the passage of air to the breathing pores so that water loss is reduced. The picture shows a flower bud of Mesembryanthemum guerichianum.

A rather uncommon adaptation is that in which young parts of the plant are sticky, so that when sand is blown unto them, the grains form a protective coating. This occurs in Psammophora and Arenifera, two genera which derive their names from this phenomenon (sand bearer in Greek, resp. Latin) but also in about 50 other species, both succulent and non-succulent. The pictures show Crassula columnaris v. prolifera (above) and Psammophora modesta (below).


EVASION
Unlike animals, plants can not move away when the going gets tough. They have to endure the bad times in situ and that is one of the reasons why we find many succulents in shade: under shrubs, in rock crevices etc.


There are many advantages in sheltering under another plant: less sun, less wind, lower temperatures, difficult to be found and reached by browsing animals.  In these 2 cases (Haworthia arachnoidea above and Gasteria disticha below), only the inflorescences give away the fact that there is a succulent hiding in these bushes — and you have to look very carefully to find the rest of the plant itself.


Hiding underground also minimises water loss from the surface of the plant. Experiments have shown that in plants such as this Lithops julii ssp. fulleri, the loss is about a fifth lower in plants that are buried than in exposed ones.  

RECYCLING 
Many members of the mesemb family, especially the dwarf ones, are able to recycle water from old leaves to new ones.
As the soil dries out, the older leaves are gradually sacrificed and their water content is translocated to and stored in the younger ones.
Within each old pair of leaves a new, but somewhat smaller one develops and stays dormant, while the dry remains of the old leaves form a protective layer of insulation for the new ones. When the rainy period starts again, the new pair bursts through the old skin, ready for action. It has been found that this adaptation enables plants to survive for about a year without any moisture from outside.

Mesembryanthemum (Prenia) sladenianum is a well known example of this phenomenon

Below are pictures of  Antimima pumila in the growing season (early September), at the end of October  and in high summer 3 months later, showing different stages of water recycling.

 

Three hundred posts later

When I started this blog just over two years ago, I had no idea what I was letting myself in for. Actually it looked easy :
I had a lot of pictures people might be interested in and after a lifetime of growing, studying and photographing succulents, it should not be difficult to write some texts as well.
And yes, it is as simple as that: you select a few pictures, write a couple of words and hey presto, another post ready. Well, sometimes. Not so very often; rarely in fact.
Stumbling blocks may be:
–not enough good pictures to tell a story
–enough pictures but nothing special
–too little info on the subject
–too busy to do research
–plants can’t be identified properly.
This list is far from exhaustive, but you’ll get my drift I suppose.

The accompanying pictures illustrate the last of the problems mentioned above. They were taken a few km northeast of Montagu, on 9 Oct. 2013.
From the start is was clear that the plants belonged to Haworthia arachnoidea. But which variety? The first option is var. arachnoidea.
In his “Haworthia revisited”, Bruce Bayer says: “This variety often occurs on southern slopes where it is embedded in moss and lichen, and thus very moist in the winter months. The basic leaf colouration is darkish-green and the marginal spines are white”.
This description fits the bill (see first picture), but the distribution area is given as the Worcester/Robertson Karoo, which is west, rather than northeast of Montagu.
When I looked at the pictures once again, I realized that some plants looked like var. nigricans, which is decribed as: “distinguished by the purplish colouration towards the tips of the leaves and the generally darker colour” (picture 2). This variety is known from around Oudtshoorn in the east to the area between Barrydale and Montagu in the west (but not as far west as the locality where this picture was taken).

hawoaracara 8820

hawoaracara 8822

Here endeth the lesson and my 300th post.

First post

This is the beginning of a blog that is focused on two topics. Firstly on anything that has to do with succulent plants, especially those growing in South Africa, because that is were I live.
Secondly on photographing plants, succulent or not, cultivated or in the wild.
These two things have kept me busy for many years and I have written and lectured on them for almost as long. I have the privilege of living in an area where interesting succulents grow almost on my doorstep and as I am retired I have lots of time to study and photograph them
.
Haworthia arachnoidea v. nigricans along the road near my home

I hope to provide you regularly with interesting information on these subjects. It would be great to hear from you and learn what you are interested in. Therefore I invite you to share your ideas, questions, comments and opinions with other readers.
If you would like to get some more idea of who I am and what I do, please have a look at my website www.noltee.com.