Nature's fortress: How cacti keep water in and predators out - Lucas C. Majure

Prevodilac: Ivana Vojnić Tunić Lektor: Ivana Korom

If you were a jackrabbit hopping through the desert,

Da si zec koji skakuće kroz pustinju,

you’d be glad to stumble— well, maybe not stumble—

bilo bi ti drago da naletiš, zapravo, možda ne baš da naletiš,

across a cactus: the succulent flesh of these plants is a water source

na kaktus: sočno tkivo ovih biljaka je izvor vode

for many desert animals.

mnogim pustinjskim životinjama.

Native to the Americas and known for their spines and succulent stems,

Poreklom iz Amerike, a poznati po bodljama i mesnatom stablu,

cacti of all shapes and sizes have evolved to not just survive, but thrive,

kaktusi raznih vrsta nisu samo uspeli da prežive, već i da se razviju

in some of the harshest desert climates on Earth.

u najoštrijim pustinjskim klimama na Zemlji.

So how do they do it?

Kako im je to pošlo za rukom?

A cactus’s spines are one key to its survival—

Bodlje kaktusa predstavljaju jedan od ključnih faktora njihovog opstanka,

but not for the reason you might think.

ali razlog tome i nije tako očigledan.

Take a look at the prickly pear.

Uzmimo za primer bodljikavu krušku.

Its spines are highly modified leaves.

Njene bodlje su zapravo visoko modifikovani listovi.

A normal leaf’s large surface area would be ill-suited to the desert,

Velika površina tipičnog lista bila bi neprikladna za pustinju,

transpiring massive amounts of water under the baking sun.

jer bi ogromne količine vode isparile zbog sunca koje prži.

The dramatically reduced surface area of the spines limits water loss.

Znatno smanjena površina bodlji sprečava gubitak vode.

They also shade the cactus and reflect the sun’s rays,

Takođe, trnje štiti kaktus i reflektuje sunčeve zrake,

reducing the plant's core temperature during the heat of the day.

smanjujući tako temperaturu kaktusa tokom vrelog dana.

Then, at night, when air temperatures plummet,

A noću, kada temperatura vazduha opadne,

the spines act as an insulating layer,

bodlje pružaju izolacioni sloj

keeping the cactus from cooling down too much.

koji sprečava da se kaktus smrzne.

These functions are just as important, if not more,

Ove uloge bodlji su isto toliko značajne, ako ne i više,

than defending against predators.

od odbrane od strane predatora.

From Cuba to Mexico, and as far south as Brazil and Peru,

Od Kube do Meksika, pa ka jugu, sve do Brazila i Perua,

Melon cacti grow on limestone soils in seasonally dry tropical forests,

kaktus dinje raste na krečnjaku u sezonsko sušnim tropskim šumama

where they're constantly exposed to the beating sun.

gde je bez prestanka izložen izuzetno jakom suncu.

They rely on another adaptation common to cacti: a thick skin,

On upotrebljava drugu vrstu prilagođavanja osobenu za kaktuse: debelu pokoricu

which is coated in a waxy substance called a cuticle that limits water loss.

prekrivenu voskastom materijom zvanom kutikula koja sprečava gubitak vode.

Meanwhile, the stomata—

U međuvremenu, stome,

tiny holes that allow the exchange of gases that enable photosynthesis—

sitni otvori preko kojih se razmenjuju gasovi koji omogućavaju fotosintezu,

remain firmly closed until night when they open.

ostaju čvrsto zatvorene dok ne padne veče kada se one otvaraju.

The lower temperatures at night mean the cactus loses less water

Zbog niže temperature tokom noći, kaktus gubi manje vode

from the stem when the stomata open.

iz stabla kada se stome otvore.

The bulk of the plant acts as a large barrel of water,

Najveći deo biljke ponaša se kao ogromno bure puno vode

storing it for times of need.

koje je čuva kada mu zatreba.

But to survive the desert, a cactus can’t just limit water loss—

Međutim, kako bi preživeo u pustinji, kaktus mora ne samo da spreči gubitak vode

it has to be prepared to take full advantage

već da i maksimalno iskoristi

of the rare situations where water is readily available.

retke situacije kada je voda lako dostupna.

In North America’s Sonoran Desert,

U severnoameričkoj Sonorskoj pustinji,

the towering Saguaro cactus can grow up to 20 meters tall

veličanstveni kaktus saguaro može da naraste do 20 metara visine

and live for up to 200 years.

i živi do 200 godina.

Woody tissue, like the kind found in tree trunks,

Drvenasto tkivo, slično onome kao kod debla,

give the Saguaro its height,

zaslužno je za visinu saguara,

but the Saguaro survives with way less water than most trees.

ali ovaj kaktus zahteva mnogo manje vode nego većina drveća.

Most of its roots are only a few inches deep.

Njegovo korenje se uglavnom pruža tek nekoliko centimetara u dubinu.

Just below the soil’s surface, they spread out laterally for meters

Tik ispod površine zemljišta, korenje se grana nekoliko metara horizontalno

and hold the plant in place.

i daje oslonac biljci.

Even its single deepest root, the taproot,

Čak se i njen najduži koren

extends less than one meter into the ground.

pruža manje od jednog metra u zemlju.

After a rain, the lateral roots respond in real time,

Nakon kiše, bočno korenje odmah

rapidly growing and spreading.

kreće da ubrzano raste i širi se.

They produce ephemeral rain roots that quickly take up the available water.

Ono stvara efemerno kišno korenje koje brzo upija dostupnu vodu.

The water is then pulled up into the plant body

Voda zatim putuje u telo biljke

and stored in cells that contain mucilage,

i pohranjuje se u ćelijama koje sadrže sluz,

a gluey substance that clings to water molecules

lepljivu materiju koja se kači za molekule vode

and stops them from evaporating if the plant’s tissue

i sprečava njihovo isparavanje za slučaj da je tkivo

is ever damaged and exposed.

ikada oštećeno ili ugroženo.

As the soil dries after the rain,

Kako se zemljište suši posle kiše,

the small rain roots also start to dry and wither away,

tako se i sitno kišno korenje suši i vene

and the cactus awaits the next time it can take advantage of a shower.

dok kaktus čeka na sledeću priliku za kupanje.

Taken together, these features make cacti well-equipped to survive

Sve ove karakteristike zajedno omogućavaju kaktusima da prežive

their environments,

u raznim sredinama,

from the driest desert to... a tropical rainforest?

od sušnih pustinja do... prašuma?

The mistletoe cactus can live on the branches of trees in the rainforest.

Kaktus imele može da živi na granama drveća u prašumi.

Though there’s lots of water around, not much of it reaches the cactus here,

Iako je sredina izuzetno vlažna, voda ne dopire do kaktusa u velikoj meri

and there's nowhere for its roots to go.

i nema mesta za njegovo korenje.

So even here, the cactus survives using adaptations

Ali čak i ovde, kaktus uspeva da se prilagodi, služeći se taktikama

that long ago helped its ancestors survive the desert.

koje su njegovim prethodnicima nekada davno pomogle da prežive u pustinji.