Stomatal properties of Arabidopsis cauline and rice flag leaves and their contributions to seed production and grain yield

Abstract

Cauline leaves on the inflorescence stem of Arabidopsis thaliana may play important roles in supplying photosynthetic products to sinks, such as floral organs. Flag leaves in rice (Oryza sativa) have a higher photosynthetic capacity than other leaves and are crucial for increasing grain yield. However, the detailed properties of stomata in cauline and flag leaves have not been investigated. In Arabidopsis, stomatal conductance and CO2 assimilation rate were higher in cauline leaves under white light than in rosette leaves, consistent with higher levels of plasma membrane (PM) H +-ATPase, a key enzyme for stomatal opening, in guard cells. Moreover, removal of cauline leaves significantly reduced the shoot biomass by approximately 20% and seed production by approximately 46%. In rice, higher stomatal density, stomatal conductance, and CO2 assimilation rate were observed in flag leaves than in fully expanded second leaves. Removal of the flag leaves significantly reduced grain yield by approximately 49%. Taken together, these results show that cauline and flag leaves have important roles in seed production and grain yield through the enhanced stomatal conductance and CO2 assimilation rate.

Modulation of cell differentiation and growth dynamics underlie the shift from bud protection to light capture in cauline leaves

“…This role is analogous to the way sepals shield developing internal organs of flowers (Fig. 1C) (Pabõn-Mora et al, 2013; Ding et al, 2023). The presence of abaxial trichomes on cauline leaves reinforces their protective function (Fig.…”

“…In contrast to rosette leaves, which have petioles for optimizing light capture, cauline leaves lack petioles but efficiently perform photosynthesis as they are located on the stem, so have direct access to light without being in the shade of other leaves (Fig. 1A-B) (Ding et al, 2023). Furthermore, in their early stages, cauline leaves serve as a protective covering for the inflorescence meristem.…”

“…On one hand, they are efficient photosynthetic organs, contributing to the plant’s overall energy production (Su et al, 2011). However, they also serve as protective structures for emerging floral buds during early bolting stages (Pabõn-Mora et al, 2013; Ding et al, 2023). This suggests that the development of these leaves might exhibit characteristics of both rosette leaves and laminar organs of the flower such as sepals (Hempel and Feldman, 1994; Yang and Jiao, 2016).…”

Low relative air humidity and increased stomatal density independently hamper growth in young Arabidopsis

“…Then, high stomatal numbers that potentially mediate increased CO 2 uptake may pay off in improved photosynthesis and biomass production and/or yield. For example, high stomatal conductance in Arabidopsis cauline leaves was associated with higher seed yield, similar to flag leaves in rice (Ding, Zhu & Kinoshita 2023). Further studies addressing the effects of altered stomatal densities on plant growth, biomass production and yield in later developmental stages are needed to assess the potential benefits of increased stomatal density.…”