Longitudinal Pattern of Aerenchyma Formation Using the Ti-Gompertz Model in Rice Adventitious Roots

The longitudinal pattern of root aerenchyma formation of its relationship with the function of adventitious roots in rice remains unclear. In this study, the percentage of the aerenchyma area to the cross-sectional area (i.e., aerenchyma percentage) was fit with four non-linear models, namely, W0-Gompertz, Ti-Gompertz, logistic, and von Bertalanffy. Goodness-of-fit criteria such as the R2, the Akaike information criterion (AIC), and the Bayesian information criterion (BIC) were used to select the model. The bias of the parameters was evaluated using the difference between the ordinary least squares-based parameter estimates and the mean of 1,000 bootstrap-based parameter estimates and the symmetry of the distributions of these parameters. The results showed that the Ti-Gompertz model, which had a high goodness-of-fit with an R2 close to 1, lower AIC and BIC values, parameter estimates close to being unbiased, and good linear approximation, provided the best fit for the longitude pattern of rice aerenchyma formation with different root lengths among the competing models. Using the second- and third-order derivatives according to the distance from the root apex, the critical points of Ti-Gompertz were calculated. The rapid stage for aerenchyma formation was from the maximum acceleration point (1.38–1.76 cm from the root apex) to the maximum deceleration point (3.13–4.19 cm from the root apex). In this stage, the aerenchyma percentage increased by 5.3–15.7% per cm, suggesting that the cortical cells tended to die rapidly for the aerenchyma formation rather than for the respiration cost during this stage. Meanwhile, the volume of the aerenchyma of the entire roots could be computed using the integral function of the Ti-Gompertz model. We proposed that the longitudinal pattern of root aerenchyma formation modeled by the Ti-Gompertz model helped to deeply understand the relationship between the anatomical traits and physiological function in rice adventitious roots.

Methane flux from high-yielding Inpari rice varieties in Central Java, Indonesia

<p>Rice cultivation is a source of greenhouse gas emissions, particularly methane (CH₄). One of the factors that affect CH₄ emissions from rice fields is rice cultivar. In this study, a field experiment was conducted to determine CH₄ emissions from various high-yielding inbred varieties and the relationship between CH₄ emissions and rice growth parameters. The field experiment was conducted in Jaken, Pati Regency, Central Java province, during the wet season of 2014/2015. The experiment was arranged using a randomized block design with three replications and several cultivar treatments (Inpari 13, 18, 19, 20, 23, 24, 29, 30, 31, 32, and 33, with Ciherang as the comparison cultivar). The data collected includes CH₄ flux, plant height, tiller number, biomass, grain yield, and root aerenchyma area. The CH₄ flux was measured at several critical growth stages. The Inpari 24, Inpari 13, and Inpari 19 demonstrated CH₄ emissions reduced by as much as 36.1%, 32.8%, and 21.3%, respectively, compared to Ciherang. The Inpari 13 and Inpari 24 varieties had significantly lower emission indices than Ciherang and the other Inpari varieties, with 17 and 20 g CH₄ per 1 kg grain yield, respectively. CH₄ flux was found to correlate significantly with tiller number per hill, total biomass, and root aerenchyma area at the panicle initiation growth stage.</p>

Anatomical, morphological and growth responses of Thinopyrum ponticum plants subjected to partial and complete submergence during early stages of development

Seedling recruitment and growth of forage grasses in flood-prone grasslands is often impaired by submergence. We evaluate the responses of Thinopyrum ponticum (Podp.) Barkw. &amp; Dewey to partial and complete submergence at two early stages of development. Two greenhouse experiments were carried out with plants at three expanded leaves (Experiment 1) or five expanded leaves stage (Experiment 2). In each case, three treatments were applied for 14 days: control (C), partial submergence (PS; water level to half plant height), and complete submergence (CS; water level to 1.5 times plant height). Submergence was followed by a recovery period of 14 days at well drained conditions. Assessments included plant survival, height, leaf blade and pseudostem length, soluble carbohydrates in pseudostem, and shoot and root dry mass accumulation at the beginning and end of the submergence, and at the end of the recovery period. Root aerenchyma formation was determined on day 14 in both experiments. Under PS all plants survived, and the impact of the stress was related to the plants’ developmental stage. However, plants with five expanded leaves increased total plant biomass with respect to control by 48%, plants with three expanded leaves reduced it by the same percentage. This response could be related to a higher ability to form root aerenchyma (17 vs 10%), and an enhanced leaf de-submergence capacity due to promoted leaf blade and pseudostem lengthening. Complete submergence treatment compromised the survival of 70% of the individuals with three expanded leaves but did not affect the survival at the five expanded leaves stage. In any developmental stage (three or five expanded leaves) plants fail to promote enough elongation of leaf blades or pseudostems to emerge from the water, so that always remained below the water surface. Root aerenchyma was not increased by CS at either of these two plant developmental stages. The high amount and concentration of pseudostem total soluble carbohydrates of the larger (five expanded leaves) plants facilitated their recovery growth after submergence. Our results predict the successful introduction of this species in areas where water excesses can cause soil waterlogging or shallow-partial plant submergence, but suggest avoidance of areas prone to suffer high-intensity flooding that lead to full plant submergence as this would highly constrain plant recruitment.

Rice annexin OsANN4 interacting with OsCDPK24, reduces root aerenchyma formation by modulating H2O2 under ABA treatment

Plant annexins are calcium- and lipid-binding proteins that have multiple functions, and a significant amount of research on plant annexins has been reported in recent years. However, the functions of annexins in diverse biological processes in rice are largely unclear. Herein, we report that OsANN4, a calcium-binding rice annexin protein, is a substrate for OsCDPK24, and the OsANN4 phosphorylation site is the 13th serine, which is a key site for phosphorylation. Most strikingly, abscisic acid (ABA) promotes the interaction between OsANN4 and OsCDPK24. Moreover, knocking down OsANN4 by RNA interference resulted in visible and invisible phenotypes with exogenous ABA treatment, such as shorter shoots of seedlings, less lateral roots, earlier root aerenchyma formation and so on. The further analyzed results showed that decreased superoxide dismutase (SOD) and catalase (CAT) activity of the RNAi lines, which control H2O2 accumulation for redox homeostasis, and further promoted earlier aerenchyma formation of the root. These results suggest that a proposed molecular mechanism exists between OsANN4 and H2O2 production to response ABA.HighlightOsANN4 enhances SOD and CAT activities to scavenge H2O2 to alleviate the formation of aerenchyma under ABA treatment. OsCDPK24 interacts with and phosphorylates OsANN4, this interaction strengthened under ABA treatment.

Anatomical responses of jute (Corchorus capsularis L. cv. D‐154) to waterlogging

The effect of waterlogging (about 2 cm depth for 14 days) on anatomical structure in jute (Corchorus capsularis L. cv. D-154) plants grown in sand culture experiment was studied. Waterlogging resulted in the development of adventitious root, aerenchyma in the cortex of the stem. It also caused a decrease in vascular area as well as size of the vessels having smaller cavity in the root, stem and leaves. Pith area was found to increase in stem under waterlogging condition. Reduced number and closed stomata were found under waterlogging condition. Dhaka Univ. J. Biol. Sci. 27(2): 213-219, 2018 (July)