http://nhjy.hzau.edu.cn/kech/ssyy/pdf/drought/4.PDF

Photosynthesis under drought and salt stress: regulation mechanisms from whole plant to cell

Photosynthesis is one of the key processes to be affected by water deficits, via decreased CO2 diffusion to the chloroplast and metabolic constraints. The relative impact of those limitations varies with the intensity of the stress, the occurrence (or not) of superimposed stresses, and the species we are dealing with. Total plant carbon uptake is further reduced due to the concomitant or even earlier inhibition of growth. Leaf carbohydrate status, altered directly by water deficits or indirectly (via decreased growth), acts as a metabolic signal although its role is not totally clear. Other relevant signals acting under water deficits comprise: abscisic acid (ABA), with an impact on stomatal aperture and the regulation at the transcription level of a large number of genes related to plant stress response; other hormones that act either concurrently (brassinosteroids, jasmonates, and salycilic acid) or antagonistically (auxin, cytokinin, or ethylene) with ABA; and redox control of the energy balance of photosynthetic cells deprived of CO2 by stomatal closure. In an attempt to systematize current knowledge on the complex network of interactions and regulation of photosynthesis in plants subjected to water deficits, a meta-analysis has been performed covering >450 papers published in the last 15 years. This analysis shows the interplay of sugars, reactive oxygen species (ROS), and hormones with photosynthetic responses to drought, involving many metabolic events. However, more significantly it highlights (i) how fragmented and often non-comparable the results are and (ii) how hard it is to relate molecular events to plant physiological status, namely photosynthetic activity, and to stress intensity. Indeed, the same data set usually does not integrate these different levels of analysis. Considering these limitations, it was hard to find a general trend, particularly concerning molecular responses to drought, with the exception of the genes ABI1 and ABI3. These genes, irrespective of the stress type (acute versus chronic) and intensity, show a similar response to water shortage in the two plant systems analysed (Arabidopsis and barley). Both are associated with ABA-mediated metabolic responses to stress and the regulation of stomatal aperture. Under drought, ABI1 transcription is up-regulated while ABI3 is usually down-regulated. Recently ABI3 has been hypothesized to be essential for successful drought recovery.

/pdf/photosynthesis-and-drought-can-we-make-metabolic-connections-50uqjztojl.pdf

Photosynthesis and drought: can we make metabolic connections from available data?

Drought and salinity (i.e. soil water stress) are the main environmental factors limiting photosynthesis and respiration and, consequently, plant growth. This review summarizes the current status of knowledge on photosynthesis and respiration under water stress. It is shown that diffusion limitations to photosynthesis under most water stress conditions are predominant, involving decreased mesophyll conductance to CO 2 , an important but often neglected process. A general failure of photochemistry and biochemistry, by contrast, can occur only when daily maximum stomatal conductance (g s ) drops below 0.05-0.10 mol H 2 O m -2 s -1 . Because these changes are preceded by increased leaf antioxidant activities (g s below 0.15-0.20 mol H 2 O m -2 s -1 ), it is suggested that metabolic responses to severe drought occur indirectly as a consequence of oxidative stress, rather than as a direct response to water shortage. As for respiration, it is remarkable that the electron partitioning towards the alternative respiration pathway sharply increases at the same g s threshold, although total respiration rates are less affected. Despite the considerable improvement in the understanding of plant responses to drought, several gaps of knowledge are highlighted which should become research priorities for the near future. These include how respiration and photosynthesis interact at severe stress, what are the boundaries and mechanisms of photosynthetic acclimation to water stress and what are the factors leading to different rates of recovery after a stress period.

Keeping a positive carbon balance under adverse conditions: responses of photosynthesis and respiration to water stress

* Whether photosynthesis is limited during water stress and recovery because of diffusive or biochemical factors is still open to debate, and apparent contradictions appear when various studies on species with different growth forms are compared. * Ten Mediterranean species, representing different growth forms, were subjected to different levels of water stress, the most severe followed by rewatering. A quantitative limitation analysis was applied to estimate the effects of water stress on stomatal (S(L)), mesophyll conductance (MC(L)) and biochemical limitations (B(L)). * Results confirmed a general pattern of photosynthetic response to water stress among C(3) plants when stomatal conductance (g(s)) is used as a reference parameter. As g(s) values decreased from a maximum to approx. 0.05 mol H(2)O m(-2) s(-1), the total photosynthetic limitation rose from 0 to approx. 70%, and this was caused by a progressive increase of both S(L) and MC(L) limitations, while B(L) remained negligible. When lower values of g(s) were achieved (total photosynthetic limitation increased from 70 to 100%), the contribution of S(L) declined, while MC(L) still increased and B(L) contributed significantly (20-50%) to the total limitation. * Photosynthetic recovery of severely stressed plants after rewatering showed a dominant role of MC(L), irrespective of the degree of photosynthesis recovery.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2007.02087.x

Photosynthetic limitations in response to water stress and recovery in Mediterranean plants with different growth forms

Drought is one of the major constraints limiting crop production worldwide. Crop growth models predict that this issue will be more severe in future. Drought impairs normal growth, disturbs water relations, and reduces water use efficiency in plants. Plants, however, have a variety of physiological and biochemical responses at cellular and whole organism levels, making it a more complex phenomenon. The rate of photosynthesis is reduced mainly by stomatal closure, membrane damage, and disturbed activity of various enzymes, especially those involved in ATP synthesis. Plants display a range of mechanisms to withstand drought, such as reduced water loss by increased diffusive resistance, increased water uptake with prolific and deep root systems, and smaller and succulent leaves to reduce transpirational loss. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols also play vital roles in sustaining cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberellins, cytokinins, and abscisic acid modulate plant responses toward drought. Polyamines, citrulline, and several enzymes act as antioxidants and reduce adverse effects of water deficit. Plant drought stress can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection, and exogenous application of hormones and osmoprotectants to seeds or growing plants, as well as engineering for drought resistance. Here, we provide an overview of plant drought stress, its effects on plants’ resistance mechanisms and management strategies to cope with drought stress.

Drought stress in plants: an overview

Recovery responses of photosynthesis, transpiration, and stomatal conductance in kidney bean following drought stress

PROBLEM TO BE SOLVED: To provide a means capable of detecting with high sensitivity and ease defects in a filter, without having to apply a load to the filter, and without having to require the time and the labor for pretreatment and after-treatment. SOLUTION: In this inspection method for the filter, fine particles are generated, the fine particles are introduced from one side of the filter into the filter, an intensified directivity of light is generated, the light is transmitted through the other side of the filter, vibration of the air is generated further in the other side of the filter, and the fine particles are irradiated with the light to have the fine particles visualized, while being moved, discharged from the other side of the filter by the vibration of the air. COPYRIGHT: (C)2009,JPO&INPIT

Inspection method and inspection device for filter

Disclosed is a semiconductor manufacturing system that has a program for inspecting a semiconductor manufacturing device, the program being configured to execute: a step of displaying a screen for designating an inspection matter consisting of inspection items including operation items and verification items; a step of reading out the inspection items corresponding to the designated inspection matter from a storage section, sorting the inspection items in the order of the workflow, and displaying each inspection item on the screen along with an execution attribute which indicates whether that inspection item is to be processed under automatic execution or under manual execution; and a step of accepting an inspection start command and then reading out the first inspection item from the storage section. The program also executes steps corresponding to the following cases (a) to (d) until there are no more inspection items: (a) in a case where the inspection item is an operation item and the execution attribute is automatic execution; (b) in a case where the inspection item is an operation item and the execution attribute is manual execution; (c) in a case where the inspection item is a verification item and the execution attribute is automatic execution; and (d) in a case where the inspection item is a verification item and the execution attribute is manual execution.

Semiconductor manufacturing system

PROBLEM TO BE SOLVED: To completely eliminate the need for supply of energy such as electric power, to meet demands for energy-saving, and to provide utilization even in mountainous areas or the like wherein supply of energy such as electric power is difficult. SOLUTION: The sloping ground utilizing type environment control system is provided with one or a plurality of underground passages 1 buried in sloping ground G along its slope and cooled by the earth temperature, an outside air intake port 3 connected to an upper end of the underground passage, and an air discharge port 5 provided in an internal space of a structure VH and connected to a lower end of the underground passage. Air in the underground passage 1 is cooled in the underground passage, it flows down in the underground passage, and it is discharged into the internal space of the structure VH from the air discharge port 5. Following downflow of the air in the underground passage 1, outside air is taken into the underground passage from the outside air intake port 3. COPYRIGHT: (C)2008,JPO&INPIT

Sloping ground utilizing type environment control system

PROBLEM TO BE SOLVED: To provide a defect detection method for preventing a beam of laser light from entering into an end face of a honeycomb structure and an open end of cells, and sensitively detecting a defect in the honeycomb structure. SOLUTION: In the defect detection method, a grid-like antireflection member 20 for covering one end face 12a is disposed on one end face 12a of the cylindrical honeycomb structure 12 formed with a plurality of the cells partitioned by a porous partitions. Fine particles are introduced into the honeycomb structure 12 from the other end face of the honeycomb structure 12, pass through the antireflection member 20, and are discharged from one end face 12a. After the fine particles pass through the antireflection member 20, they are irradiated with the beam of laser light 13 parallel to one end face 12a, and visualized. COPYRIGHT: (C)2009,JPO&INPIT

Koichi Miyashita

Papers

Recovery responses of photosynthesis, transpiration, and stomatal conductance in kidney bean following drought stress

Inspection method and inspection device for filter

Semiconductor manufacturing system

Sloping ground utilizing type environment control system

Defect detection method and defect detector