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.
Make Pan-Fried Top Sirloin Steak. 1  1. Cut the steak into serving sized portions. 2  2. Place a cast iron skillet or a frying pan over medium high heat on the stove. 3  3. Place the steaks in the center of the pan.  4. Continue turning the steaks every thirty seconds until they are cooked. For rare steaks, cook for a total of 1 1/2 minutes on each side. For medium rare steaks, cook for a total of 2 minutes on each side. For medium well steaks, cook for a total of 2 1/2 minutes on each side.