背景:茎倒伏(植物茎或茎在收获之前的过早断裂)是一种持续的农业问题,每年导致数十亿美元的产量损失。三点弯曲试验,和外皮穿刺试验是用于研究作物对倒伏的敏感性的常见生物力学测量。然而,测试速率对这些生物力学测量的影响尚不清楚。总的来说,众所周知,生物标本(包括植物茎)表现出粘弹性机械性能,因此,它们的机械响应取决于它们偏转的速率。然而,文献中关于测试速率(aka位移速率)对弯曲刚度的影响的信息很少,植物茎的弯曲强度和外皮穿刺测量。
结果:以不同的速率对完全成熟和衰老的玉米茎和小麦茎进行了三点弯曲测试。还以各种速率对玉米茎进行了果皮渗透测试。测试速率对从三点弯曲测试获得的弯曲刚度和弯曲强度计算的影响很小。Rind穿刺测量显示出强的速率依赖性效应。随着穿刺率的增加,穿刺力下降。这是出乎意料的,因为当速率增加时,粘弹性材料通常显示阻力增加。
结论:测试率影响完全成熟和干燥植物茎的三点弯曲测试结果和外皮穿刺测量。在绿色茎中,这些影响预计会更大。对植物茎进行生物力学测试时,重要的是在研究中利用一致的跨度和位移率。理想地,样品应当以与它们在体内经历的相似的速率进行测试。
BACKGROUND: Stalk lodging (the premature breaking of plant stalks or stems prior to harvest) is a persistent agricultural problem that causes billions of dollars in lost yield every year. Three-point
bending tests, and rind puncture tests are common biomechanical measurements utilized to investigate crops susceptibility to lodging. However, the effect of testing rate on these biomechanical measurements is not well understood. In general, biological specimens (including plant stems) are well known to exhibit viscoelastic mechanical properties, thus their mechanical response is dependent upon the rate at which they are deflected. However, there is very little information in the literature regarding the effect of testing rate (aka displacement rate) on flexural stiffness,
bending strength and rind puncture measurements of plant stems.
RESULTS: Fully mature and senesced maize stems and wheat stems were tested in three-point
bending at various rates. Maize stems were also subjected to rind penetration tests at various rates. Testing rate had a small effect on flexural stiffness and
bending strength calculations obtained from three-point
bending tests. Rind puncture measurements exhibited strong rate dependent effects. As puncture rate increased, puncture force decreased. This was unexpected as viscoelastic materials typically show an increase in resistive force when rate is increased.
CONCLUSIONS: Testing rate influenced three-point bending test results and rind puncture measurements of fully mature and dry plant stems. In green stems these effects are expected to be even larger. When conducting biomechanical tests of plant stems it is important to utilize consistent span lengths and displacement rates within a study. Ideally samples should be tested at a rate similar to what they would experience in-vivo.