▁of ▁leaves . ▁One ▁of ▁the ▁most ▁common ▁families ▁of ▁desert ▁plants ▁are ▁the ▁c act i , ▁which ▁are ▁covered ▁in ▁sharp ▁sp ines ▁or ▁br ist les ▁for ▁defence ▁against ▁her b iv ory . ▁The ▁br ist les ▁on ▁certain ▁c act i ▁also ▁have ▁the ▁ability ▁to ▁reflect ▁sun light , ▁such ▁as ▁those ▁of ▁the ▁old ▁man ▁c act us . ▁C ertain ▁x er oph y tes , ▁like ▁o le ander , ▁feature ▁st om ata ▁that ▁are ▁re cess ed ▁as ▁a ▁form ▁of ▁protection ▁against ▁hot , ▁dry ▁desert ▁wind s , ▁which ▁allows ▁the ▁leaves ▁to ▁retain ▁water ▁more ▁effectively . ▁Another ▁unique ▁adaptation ▁can ▁be ▁found ▁in ▁x er oph y tes ▁like ▁oc ot illo , ▁which ▁are ▁" lea fl ess ▁during ▁most ▁of ▁the ▁year , ▁thereby ▁avoid ing ▁excess ive ▁water ▁loss ". ▁ ▁There ▁are ▁also ▁plants ▁called ▁ph re at oph y tes ▁which ▁have ▁adapted ▁to ▁the ▁har sh ▁desert ▁conditions ▁by ▁developing ▁extremely ▁long ▁root ▁systems , ▁some ▁of ▁which ▁are ▁ 8 0 ▁ft . ▁long ; ▁to ▁reach ▁the ▁water ▁table ▁which ▁ens ures ▁a ▁water ▁supply ▁to ▁the ▁plant . ▁ ▁Ex pl oration ▁and ▁research ▁The ▁har sh ▁climate ▁of ▁most ▁desert ▁regions ▁is ▁a ▁major ▁obst acle ▁in ▁conduct ing ▁research ▁into ▁these ▁e cos ystem s . ▁In ▁the ▁environments ▁requiring ▁special ▁adapt ations ▁to ▁surv ive , ▁it ▁is ▁often ▁difficult ▁or ▁even ▁impossible ▁for ▁research ers