A simple method for the application of exogenous phytohormones to the grass leaf base protodermal zone to improve grass leaf epidermis development research

Abstract

Background The leaf epidermis functions to prevent the loss of water and reduce gas exchange. As an interface between the plant and its external environment, it helps prevent damage, making it an attractive system for studying cell fate and development. In monocotyledons, the leaf epidermis grows from the basal meristem that contains protodermal cells. Leaf protoderm zone is covered by the leaf sheath or coleoptile in maize and wheat, preventing traditional exogenous phytohormone application methods, such as directly spraying on the leaf surface or indirectly via culture media, from reaching the protoderm areas directly. The lack of a suitable application method limits research on the effect of phytohormone on the development of grass epidermis. Results Here, we describe a direct and straightforward method to apply exogenous phytohormones to the leaf protoderms of maize and wheat. We used the auxin analogs 2,4-D and cytokinin analogs 6-BA to test the system. After 2,4-D treatment, the asymmetrical division events and initial stomata development were decreased, and the subsidiary cells were induced in maize, the number of GMC (guard mother cell), SMC (subsidiary mother cell) and young stomata were increased in wheat, and the size of the epidermal cells increased after 6-BA treatment in maize. Thus, the method is suitable for the application of phytohormone to the grass leaf protodermal areas. Conclusions The method to apply hormones to the mesocotyls of maize and wheat seedlings is simple and direct. Only a small amount of externally applied substances are needed to complete the procedure in this method. The entire experimental process lasts for ten days generally, and it is easy to evaluate the phytohormones’ effect on the epidermis development.

Auxin/Cytokinin Antagonistic Control of the Shoot/Root Growth Ratio and Its Relevance for Adaptation to Drought and Nutrient Deficiency Stresses

“…Moreover, osmotic stress was shown to inhibit leaf expansion growth by increased auxin action via the ARF family of auxin response activators, indicating that auxin also mediates drought stress responses in the shoot [84]. Auxin may also positively impact drought tolerance by limiting stomatal density and controlling stomatal aperture [85].…”

“…On the other hand, decreased cytokinin content was associated with increased membrane integrity under drought stress conditions and increased ABA sensitivity [93]. While cytokinin treatments have been shown to increase stomatal density in leaves, cytokinin is also known to counteract the effect of ABA on stomatal closure [85,100]. Recently, it was discovered that this cytokinin/ABA crosstalk regulates osmotic stress tolerance by regulating the global control of protein synthesis rates [101].…”

“…Cytokinin promotion of drought stress tolerance has been successful when cytokinin biosynthesis was increased in response to drought stress and in senescing leaves of plants expressing a cytokinin biosynthesis transgene from a senescence-or stress-inducible promoter [110][111][112][113][114][115][116][117]. These approaches circumvent the negative drought stress impact of cytokinin on developing leaves, wherein cytokinin promotes water loss by increasing stomatal density and aperture [85,100]. Therefore, the timing of cytokinin treatment seems to be crucial for promoting this type of drought stress tolerance.…”

Evolving role of synthetic cytokinin 6-benzyl adenine for drought stress tolerance in soybean (Glycine max L. Merr.)

“…Booker et al (2003) and Cai et al (2018) reported that indole-3-acetic acid (IAA) did not directly inhibit the growth of lateral buds because IAA applied at shoot apices could not enter inside the lateral buds. Although, information on the mechanism of hormonal absorption and translocation in plant tissues has not been widely reported, many studies nevertheless, found a positive correlation between growth and enhanced exogenous levels of 6-BAP which had tremendous effects on endogenous cytokinin content (Yuan et al, 2019;Li et al, 2021;Zhang et al, 2021). Liu and Zhang (2017), reported foliar application of exogenous 6-BAP to improve plant drought stress resistance by increasing the rate of photosynthesis, stomatal conductance, and transpiration rates, reducing yield losses up to 46% in soybean.…”

Characterization of anatomical features, developmental roadmaps, and key genes of bamboo leaf epidermis

“…The transcriptional network responsible for this subdivided development was also revealed (Gao, Guo, Chen, et al, 2021a). The leaf epidermis plays an important role in regulating transpiration and is the first line of defense against biological and abiotic invasion (Li et al, 2021). In addition, the epidermis not only forms a protective barrier against the environment (Yeats & Rose, 2013), but also plays a role in growth control (Czesnick & Lenhard, 2015).…”