Consiglio Nazionale delle Ricerche C.S., Olivicoltura, Via Madonna Alta, 06100 Perugia, Italy.
Plant Physiol. 1989 Aug;90(4):1408-16. doi: 10.1104/pp.90.4.1408.
The effects of two levels of salinity on photosynthetic properties of olive (Olea europea L.) leaves were observed either in low or in high H(2)O vapor pressure deficit (vpd). Under moderate salt stress, stomata were found to be less open and responsive both to light and vpd, but the predominant limitation of photosynthesis was due to the mesophyll capacity of CO(2) fixation. We elaborate a procedure to correlate mesophyll capacity and liquid phase diffusive conductance. The estimated liquid phase diffusive conductance was reduced by salt and especially by high vpd; morphological and physiological changes could be responsible for this reduction. As a result, the chloroplast CO(2) partial pressure was found to decrease both under salt and vpd stress, thus resulting in a ribulose-1,5-bisphosphate carboxylase limitation of assimilation. However, under combined salt and vpd stress, O(2) sensitivity of assimilation increased, as would be expected under conditions of limiting ribulose 1,5-bisphosphate regeneration. Fluorescence induction measurements indicated that, under these conditions, energy supply may become limiting. When Cl(-) concentration exceeded 80 millimolar in tissue water, zero growth and 50% leaf drop was observed. Fluorescence induction showed irreversible damage at Cl(-) levels higher than 200 millimolar and basal leaves reached this concentration earlier than the apical ones.
在低或高 H(2)O 蒸汽压亏缺（vpd）条件下，观察了两种盐度水平对橄榄（Olea europea L.）叶片光合作用特性的影响。在适度盐胁迫下，发现气孔对光和 vpd 的响应性降低，但光合作用的主要限制因素是 CO(2)固定的叶肉能力。我们详细描述了一种关联叶肉能力和液相扩散导度的方法。盐度特别是高 vpd 降低了估计的液相扩散导度；形态和生理变化可能是导致这种降低的原因。结果发现，在盐和 vpd 胁迫下，叶绿体 CO(2)分压均降低，从而导致核酮糖-1,5-二磷酸羧化酶同化作用受限。然而，在盐和 vpd 联合胁迫下，同化作用对 O(2)的敏感性增加，这在限制核酮糖 1,5-二磷酸再生的条件下是预期的。荧光诱导测量表明，在这些条件下，能量供应可能会受到限制。当组织水中的 Cl(-)浓度超过 80 毫摩尔时，观察到零生长和 50%的叶片脱落。荧光诱导显示在 Cl(-)水平高于 200 毫摩尔时会发生不可逆损伤，并且基生叶比顶生叶更早达到该浓度。
