Cleland R E, Buckley G, Nowbar S, Lew N M, Stinemetz C, Evans M L, Rayle D L
Department of Botany, University of Washington, Seattle 98195, USA.
Planta. 1991;186:70-4.
The acid-growth theory predicts that a solution with a pH identical to that of the apoplast of auxin-treated tissues (4.5.-5.0) should induce elongation at a rate comparable to that of auxin. Different pH profiles for elongation have been obtained, however, depending on the type of pretreatment between harvest of the sections and the start of the pH-incubations. To determine the acid sensitivity under in vivo conditions, oat (Avena sativa L.) coleoptile, maize (Zea mays L.) coleoptile and pea (Pisum sativum L.) epicotyl sections were abraded so that exogenous buffers could penetrate the free space, and placed in buffered solutions of pH 3.5-6.5 without any preincubation. The extension, without auxin, was measured over the first 3 h. Experiments conducted in three laboratories produced similar results. For all three species, sections placed in buffer without pretreatment elongated at least threefold faster at pH 5.0 than at 6.0 or 6.5, and the rate elongation at pH 5.0 was comparable to that induced by auxin. Pretreatment of abraded sections with pH-6.5 buffer or distilled water adjusted to pH 6.5 or above gave similar results. We conclude that the pH present in the apoplast of auxin-treated coleoptile and stems is sufficiently low to account for the initial growth response to auxin.
酸生长理论预测，一种pH值与生长素处理组织的质外体相同（4.5 - 5.0）的溶液，应该能以与生长素相当的速率诱导伸长。然而，根据切片收获与pH孵育开始之间的预处理类型，已获得了不同的伸长pH曲线。为了确定体内条件下的酸敏感性，对燕麦（ Avena sativa L.）胚芽鞘、玉米（ Zea mays L.）胚芽鞘和豌豆（ Pisum sativum L.）上胚轴切片进行擦伤处理，以便外源缓冲液能够穿透自由空间，并将其置于pH 3.5 - 6.5的缓冲溶液中，不进行任何预孵育。在最初3小时内测量无生长素情况下的伸长情况。在三个实验室进行的实验产生了相似的结果。对于所有这三个物种，未经预处理置于缓冲液中的切片在pH 5.0时的伸长速度至少比在pH 6.0或6.5时快三倍，并且在pH 5.0时的伸长速率与生长素诱导的伸长速率相当。用pH 6.5缓冲液或调至pH 6.5及以上的蒸馏水对擦伤切片进行预处理，得到了相似的结果。我们得出结论，生长素处理的胚芽鞘和茎的质外体中存在的pH值足够低，足以解释对生长素的初始生长反应。
