Montgomery Jill A, Bressan Ray A, Mitchell Cary A
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907-2010, USA.
J Am Soc Hortic Sci. 2004 May;129(3):339-43.
Obtaining uniform mechano-dwarfing of Arabidopsis thaliana (L.) Heynh. seedlings within dense plantings is problematic. Alternative forms of mechano-stimulation were applied to seedlings in effort to obtain uniform growth reduction compared with undisturbed controls in both greenhouse and controlled growth environments. Arabidopsis grown under low photosynthetic photon flux (PPF) artificial light grew upright with limited leaf expansion, which enhanced mechano-responsiveness compared to that of rosette-growing plants under filtered sunlight or high PPF artificial light. Hypocotyls of seedlings grown at PPFs > 60 micromoles m-2 s-1 elongated less and had 6% less sensitivity to mechanical stress than seedlings grown at PPFs < 60 micromoles m-2 s-1. Fluorescent lamps alone (F) or fluorescent plus incandescent (F+I) lamps were compared for seedling responses to mechanical stress. Under F lighting, hypocotyl elongation was reduced 25% to 40% by twice-daily brush or plate treatments, and brushed seedlings exhibited more growth reduction than did plate treatments. Seedlings grown under F+I lamps exhibited similar stress-induced growth reduction compared to seedlings grown under F only, but stressed F+I seedlings lodged to a greater extent due to excessive hypocotyl elongation. Temperature-response studies using standardized F-only lighting indicated increased hypocotyl elongation but decreased leaf expansion, and decreased mechano-responsivity to brushing over the temperature range from 20 to 28 degrees C. Daylength studies indicated similar degrees of mechano-inhibition of hypocotyl elongation over the daylength range of 12, 16, 20, and 24 hours, whereas fresh weight of stressed seedling shoots declined compared to controls. A combination of environmental growth parameters that give repeatable, visual mechanical dwarfing of Arabidopsis include low-PPF fluorescent lighting from 55 to 60 micromoles m-2 s-1, ambient temperatures from 22 to 25 degrees C, and twice-daily brush treatments.
在密集种植条件下使拟南芥幼苗实现均匀的机械矮化颇具问题。为了与温室和可控生长环境中未受干扰的对照相比，获得均匀的生长减缓，对幼苗施加了不同形式的机械刺激。在低光合光子通量（PPF）人工光照下生长的拟南芥直立生长，叶片扩展有限，与在过滤阳光或高PPF人工光照下呈莲座状生长的植株相比，其机械反应性增强。在PPF＞60微摩尔·米⁻²·秒⁻¹条件下生长的幼苗下胚轴伸长较少，对机械应力的敏感性比在PPF＜60微摩尔·米⁻²·秒⁻¹条件下生长的幼苗低6%。比较了单独使用荧光灯（F）或荧光灯加白炽灯（F+I）时幼苗对机械应力的反应。在F光照下，通过每日两次的毛刷或平板处理，下胚轴伸长减少了25%至40%，经毛刷处理的幼苗比经平板处理的幼苗生长减缓更明显。与仅在F灯下生长的幼苗相比，在F+I灯下生长的幼苗表现出类似的应激诱导生长减缓，但由于下胚轴过度伸长，受胁迫的F+I幼苗倒伏程度更大。使用标准化的仅F光照进行的温度响应研究表明，在下胚轴伸长增加的同时叶片扩展减少，并且在20至28摄氏度的温度范围内对毛刷处理的机械反应性降低。日长研究表明，在12、16、20和24小时的日长范围内，下胚轴伸长的机械抑制程度相似，而与对照相比，受胁迫幼苗地上部分的鲜重下降。能够使拟南芥实现可重复的、肉眼可见的机械矮化的环境生长参数组合包括55至60微摩尔·米⁻²·秒⁻¹的低PPF荧光光照、22至25摄氏度的环境温度以及每日两次的毛刷处理。
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