ORIGIN OF GROWTH-INDUCED WATER POTENTIAL - SOLUTE CONCENTRATION IS LOW IN APOPLAST OF ENLARGING TISSUES
ORIGIN OF GROWTH-INDUCED WATER POTENTIAL - SOLUTE CONCENTRATION IS LOW IN APOPLAST OF ENLARGING TISSUES
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DOI：
10.1104/pp.83.3.596
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发表时间：
1987-03-01
期刊：
影响因子：
7.4
通讯作者：
BOYER, JS
中科院分区：
文献类型：
--
作者：
NONAMI, H;BOYER, JS
我们开发了一种新的方法，通过对完整幼苗的根加压来测量茎组织外质体中的溶质浓度（Glycine max [L.]）。)稳定。（或Pisum sativum L.），在饱和湿度下从茎表面收集少量渗出液，并用能够测量小体积（0.5微升）的微渗透计测定溶液的渗透势。在伸长区，外体浓度非常低（相当于-0.03至-0.04兆帕斯卡的渗透电位），与在完整植物中直接用等静力湿度计测量的外体水势（-0.15至-0.30兆帕斯卡）相比可以忽略不计。大部分外质体水势由负压组成，可以用压力室测量（-0.15至-0.28兆帕斯卡）。试验表明，早期的方法包括浸润细胞内间隙或加压切割片段，导致溶质释放到外质体，并导致虚假的高浓度。这些结果表明，尽管外质体中存在少量溶质，但主要成分是张力，这是生长诱导的水势梯度的一部分。梯度源于细胞壁的延伸，这阻止了膨胀达到最大，并产生了生长诱导的水势，导致水以满足扩大速度的速率从木质部移动。梯度的大小意味着生长中的组织对水的运动有很大的阻力。
We developed a new method to measure the solute concentration in the apoplast of stem tissue involving pressurizing the roots of intact seedlings (Glycine max [L.] Merr. or Pisum sativum L.), collecting a small amount of exudate from the surface of the stem under saturating humidities, and determining the osmotic potential of the solution with a micro-osmometer capable of measuring small volumes (0.5 microliter). In the elongating region, the apoplast concentrations were very low (equivalent to osmotic potentials of -0.03 to -0.04 megapascal) and negligible compared to the water potential of the apoplast (-0.15 to -0.30 megapascal) measured directly by isopiestic psychrometry in intact plants. Most of the apoplast water potential consisted of a negative pressure that could be measured with a pressure chamber (-0.15 to -0.28 megapascal). Tests showed that earlier methods involving infiltration of intracellular spaces or pressurizing cut segments caused solute to be released to the apoplast and resulted in spuriously high concentrations. These results indicate that, although a small amount of solute is present in the apoplast, the major component is a tension that is part of a growth-induced gradient in water potential in the enlarging tissue. The gradient originates from the extension of the cell walls, which prevents turgor from reaching its maximum and creates a growth-induced water potential that causes water to move from the xylem at a rate that satisfies the rate of enlargement. The magnitude of the gradient implies that growing tissue contains a large resistance to water movement.