The predominant function of thorns, spines and prickles is deterring herbivory in a mechanical form. Not all functions of spines or glochids are limited to defence from physical attacks by herbivores and other animals.echnically speaking, many plants commonly thought of as having thorns or spines actually have prickles. Roses, for instance, have prickles. Other structures that look alike are spinose teeth, spinose apical process, stiff trichomes and stinging trichomes.
1 This will help the sirloin cook from all angles and sear in the juices.  Grill the steak with lid down for 4-5 minutes depending on thickness. When grilling steaks, you need to resist the urge to open the lid and look.
4. Marinate the steak, if desired. Top sirloin steak is a great meat to marinate, since it pairs well with many flavors. 1  Choose your favorite marinade from the store, or mix up your own with equal parts oil, vinegar and spices. 2  Place the steak in a sealable plastic bag and add the marinade.ontinue turning the steaks every thirty seconds until they are cooked. 1  For rare steaks, cook for a total of 1 1/2 minutes on each side. 2  For medium rare steaks, cook for a total of 2 minutes on each side.