Take a bite out of a plump plum or peach and you’ll immediately know the meaning of succulent, as the lovely sweet juice spurts everywhere and trickles down your chin. Take a bite out of any of the numerous plants that are actually called “succulents” and you’ll probably be sick, get diarrhea or suffer from temporary paralysis. Succulent plants consist of a vast array of plants that thrive in arid, semi-desert areas and have devised cunning ways of conserving that rarest of commodities in the desert – water. Some are so successful they consist of 95 per cent of water, in which they mix their own poisons, so that desert animals (and us) do not guzzle it all up.
While they thrive in these tough arid conditions, they are not the ideal place to begin life because seedlings are often covered by drifting sands and cannot germinate. Australia, for instance, which is mainly all desert, has very few native succulents. They can be found all over the world (except in Antarctica) and have become popular houseplants because they require little TLC to survive and can live indoors with very little water.
There has been the usual quibbling about what exactly succulents are: while all cacti are succulents, all succulents are not cacti. Some botanists include plants which store their water in tubers, culms and roots, while “growing back” during hard times, while others do not.
Frankly, succulents look like plants that suffer from a serious case of edema! That is exactly what they do: store water in their tissues – in leaves, stems and roots – which makes them look plump and bulbous as a water balloon. Saving water is top priority for these plants and they have devised cunning ways to do so. Their leaves (if they have any) may be cylindrical or even spherical. Photosynthesis may take place only in the stems, which are columnar and these along with the roots are thick and fleshy, engorged with stored water. Their roots are spread in a network just below the surface of the soil so as to catch the first drops of rain, even mist and dew.
Water loss through evapotranspiration is a major issue for these plants: normal plants may lose over 97 per cent of the water. Their roots suck up through the stomata (mouth-like pores) in their leaves, through which their vital gas exchange (Carbon-dioxide “inhaled” oxygen “exhaled”) takes place. (This massive evaporation is what causes daily thundershowers in tropical rainforests every evening.) So, the leaves and stems of succulent plants have relatively few stomata to minimise water loss. But their masterstroke lies in what is called “crassulacean acid metabolism” more conveniently called CAM, which the plants may have to varying degrees. Succinctly put: the plants keep their mouths (stomata) shut during the day, when water loss would be maximum and only open up at night to inhale the carbon-dioxide they require and the oxygen they need to exhale. This carbon dioxide is converted into malic acid and stored in vacuoles (cells which help maintain water balance) during the night and transported to the chloroplasts (cells actually conducting photosynthesis), where it is reconverted into gas so that the process of photosynthesis can take place. Pure genius jugaad involving mind-boggling chemistry but that’s Mother Nature for you!
With such tricks up its sleeve some succulents can last up to two years without water. Some grow as epiphytes (on other plants) others may grow in dry lake beds where mineral deposits make it impossible for other plants to grow. Among the toughest of this lot are probably the cacti, which are native to the New World (with a couple of species found elsewhere). The tallest of which are the saguaro, which looks like a tree and can grow to over 12m tall in its native Arizona.
Despite their general unpalatable nature there are many succulents which are useful to us: one of the best-known is Aloe-vera which is actually made into a beverage and used in ointments and lotions for skin ailments, especially in tropical countries (there are 500 species of the genus), even if it is claimed that there is no scientific proof of its efficacy.
My personal favourite succulent has got to be Jalisco, Mexico’s blue Agave out of which painstakingly tequila is distilled. There are other Agave species growing in India too, which have been used for making liquor – we have huge arid areas where these succulents grow wild.
Other local succulents which are edible include the prickly pear (a cactus), and purslane. Some have truly delightful names such as Mother of Thousand/Devil’s Backbone, which to my delight I have discovered growing in my garden! (I have just ordered a mixed bag of seedlings too.) Shamefully, most of us have little time these days to expend TLC on anything except selfies and social media to say nothing of plants that look like they need to be put on diuretics (even if many are remarkably beautiful and colorful). But the succulents hold their own, as potted plants, in botanical gardens, or growing wild and wanton in wastelands and deserts, usually armed to the teeth with spikes and hooks and poisonous fluids, daring all comers!
In a rapidly heating-up world, I sometimes wonder, will these toughies be the only botanical survivors in the frizzling conditions to come? And surely their water management and preservation systems should give us something to ponder about: they pulled CAM like a magician pulling a rabbit from a hat or batter playing a reverse sweep! Surely, we can do something like that to save our one and only planet from turning into a desiccated inferno?
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Ranjit LalLal is an author, environmentalist and bird watcher.... read more