Department of Soils and Plant Nutrition, University of California, Berkeley, California 94720.
Plant Physiol. 1973 Jan;51(1):43-7. doi: 10.1104/pp.51.1.43.
Phosphorus deficiency was induced in sugar beet plants (Beta vulgaris L. var. F5855441), cultured hydroponically under standardized environmental conditions, by removal of phosphorus from the nutrient supply at the ten leaf stage 28 days after germination. CO(2) and water vapor exchange rates of individual attached leaves were determined at intervals after P cutoff. Leaves grown with an adequate nutrient supply attained net rates of photosynthetic CO(2) fixation of 125 ng CO(2) cm(-2) sec(-1) at saturating irradiance, 25 C, and an ambient CO(2) concentration of about 250 mul l(-1). After P cutoff, leaf phosphorus concentrations decreased as did net rates of photosynthetic CO(2) uptake, photorespiratory evolution of CO(2) into CO(2)-free air, and dark respiration, so that 30 days after cutoff these rates were about one-third of the control rates. The decrease in photosynthetic rates during the first 15 days after cutoff was associated with increased mesophyll resistance (r(m)) which increased from 2.4 to 4.9 sec cm(-1), while from 15 to 30 days there was an increase in leaf (mainly stomatal) diffusion resistance (r(l)') from 0.3 to 0.9 sec cm(-1), as well as further increases in r(m) to 8.5 sec cm(-1). Leaf diffusion resistance (r(l)') was increased greatly by low P at low but not at high irradiance, r(l)' for plants at low P reaching values as high as 9 sec cm(-1).
在标准化环境条件下，通过在发芽后 28 天的十叶期从营养供应中去除磷，在水培中诱导糖甜菜植物（Beta vulgaris L. var. F5855441）缺磷。在 P 切除后，每隔一段时间就会测定单个附着叶片的 CO(2)和水蒸气交换率。在充足养分供应下生长的叶片在饱和辐照度、25°C 和环境 CO(2)浓度约为 250 μl l(-1)下，达到 125 ng CO(2) cm(-2) sec(-1)的光合作用 CO(2)固定净速率。P 切除后，叶片磷浓度降低，光合作用 CO(2)摄取、光呼吸 CO(2)释放到 CO(2)-free 空气以及暗呼吸的净速率也降低，以至于切除后 30 天，这些速率约为对照速率的三分之一。切除后 15 天内，光合速率下降与增加的叶肉阻力（r(m)）有关，r(m)从 2.4 增加到 4.9 sec cm(-1)，而从 15 天到 30 天，叶片（主要是气孔）扩散阻力（r(l)‘）从 0.3 增加到 0.9 sec cm(-1)，同时 r(m)进一步增加到 8.5 sec cm(-1)。在低光照但不是高光照下，低磷大大增加了叶片扩散阻力（r(l)‘），低磷植物的 r(l)‘值高达 9 sec cm(-1)。
