Stomata, closure

Recently, another role for ABA-cytoskeleton interactions was discovered in guard cells of Vida faba leaves [150]. ABA specifically disrupted the MTs in guard cells but not in other epidermal cells. This effect resulted in the closure of stomata. When MTs repolymerized, the stomata reopened. Interestingly, no other plant hormone could elicit such a response in the guard cells. Actually, a role for MTs in the stomata closure-opening mechanism had been proposed earlier on the grounds that the MT-disrupter, colchicine, inhibited stomatal opening in Tradescantia leaves [151]. 

Finally, another important hormonal factor (but not the last) is the abscisic acid (ABA). This compound is produced mainly in chloroplasts. Its main functions are stomata closure, seed dormancy and the inhibition of axiUaiy buds growth. The addition of ABA to in vitro embryogenic cultures inhibits the early embryo germination and stimulates the coordinated maturation of the somatic embryo. However, prolonged exposition to ABA, this element suppresses growth of the formed in vitro plants (Bozhkov et al., 2002). 

There are numerous reports in the literature of a depression in daytime CO2 uptake in non-CAM plants (see Stocker, 1960 Larcher, 1973). The occurrence of noon depression of photosynthesis (Stocker, 1960) seems to be especially common in plants growing in arid habitats, the same habitats in which CAM plants exist. However, there is a fundamental difference between the noon depression of CO2 uptake in CAM and non-CAM plants. In species without CAM, the depression is caused by stress factors such as temporary water deficit, high air temperature, or reduced atmosphere moisture. These factors cause stomata closure during midday, thus inhibiting photosynthesis. In CAM plants, however, the occurrence of the CO2 uptake depression is an essential consequence of malic acid metabolism which characterizes CAM (Kluge, 1968 b). For example, in CAM plants the depression occurs independently of the actual water status of the leaves, i.e., it occurs in nonstressed plants as well as stressed. An explanation of the coupling between malate metabolism of CAM and the daytime closure of the stomata in CAM plants is suggested in Chapter 5.3.2.2. 

Observational studies The effect of early enteral feeding in children undergoing stoma closure has been evaluated in a mid-level socioeconomic setting. Early enteral feeding was associated with a reduction in postoperative fever and wound infections compared with feeding without any specific protocol [129 ]. 

Yadav PS, Choudhury SR, Grover JK, Gupta A, Chadha R, Sigalet DL. Early feeding in pediatric patients following stoma closure in a resource limited environment. J Pediatr Surg May 2013 48(5) 977-82. 

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