Guttation is the process of exudating droplets from the tips, edges, and adaxial and abaxial surfaces of the undamaged leaves. Guttation is a natural and spontaneous biological phenomenon that occurs in a wide variety of plants. Despite its generally positive effect on plant growth, many aspects of this cryptic process are unknown.
1. Introduction
Guttation is a very common natural phenomenon in the plant kingdom. Many plant species reportedly engage in guttation, such as rice, wheat, barley, maize, tomato, potatoes, tobacco
. Guttation refers to the process of liquid seeping from the tips, edges, and adaxial and abaxial surfaces of the undamaged leaves of plant species in the form of droplets
. This usually occurs during the early morning or late hours of the day and is a complex phenomenon affected by many internal and external factors. Some factors affecting guttation include a plant’s nutritional condition, its water balance and root activity, local soil moisture, air temperature and humidity, and wind speed
. It is generally thought that the continual absorption of water by the root system causes water to accumulate in roots, which creates hydrostatic pressure; this pressure can move water upward to the leaves of the plant via the xylem duct network in the stem, forcing some water to exit through hydathodes located at surfaces of leaves to form the characteristic drops of guttation
. Guttation plays an important role in the transport of nutrients, water, proteins, enzymes, hormones, and metabolites as a plant develops and grows in size
. The study showed that plant guttation can provide a continuous non-destructive system for producing recombinant proteins, greatly increasing yield, eliminating extraction, and simplifying downstream processing
. The guttation status of plants can be used as a rapid screening technology for rice germplasm resources
. However, we do not yet fully understand the internal linkage between the guttation phenomenon and the growth dynamics of plants.
Moso bamboo (Phyllostachys edulis) is the most important bamboo species in China because of its paramount ecological, economic, and cultural value among all bamboo types. Within the last decade, considerable research has investigated the mechanism underpinning the rapid growth of bamboo shoots, including the morphological anatomy aspects, physiological responses, and molecular regulation
. Compared with trees, bamboo is a grass that has a unique vascular system that is likely linked to its special growth and development characteristics
. The shoot stage has an astounding growth rate, capable of reaching a maximum daily growth of 1 m
[10]. Water dynamics figure prominently in the facilitation of the rapid growth of bamboo shoots, and guttation is a direct indicator of a plant’s water status. However, the relationship between bamboo’s guttation and its shoots’ rapid growth is understudied, and therefore this phenomenon and its implications remain unclear.
2. The Effect of Guttation on the Growth of Bamboo Shoots
2.1. Guttation Phenomenon of Sheath Blades of Bamboo Shoots
Guttation is a common phenomenon in many plants when conditions favor absorbing water through their roots but limiting transpiration from their leaves.
The bamboo’s sheath blade was the primary site of guttation and the main organ of exudation; hydathodes also were observed on its surface (
. Water dynamics figure prominently in the facilitation of the rapid growth of bamboo shoots, and guttation is a direct indicator of a plant’s water status. However, the relationship between bamboo’s guttation and its shoots’ rapid growth is understudied, and therefore this phenomenon and its implications remain unclear.
2. The Effect of Guttation on the Growth of Bamboo Shoots
Figure 1A). As the main transpiration organ of the bamboo shoot, many stomata are expected to be distributed on the surface of the bamboo sheath as well as the sheath blade
[2].
2.2. Various Components of the Guttation Fluid from Bamboo Sheath Blades
Some studies have shown that compared with the xylem liquid phase, the guttation fluid contains fewer amino acids Figure 2D–F). Two large vessels in the single vascular bundle are responsible for water transport within the culm
[40]. Therefore, given our results, we think the in-depth study of the distribution and physiological activity of aquaporin at each cell layer along the vascular bundle is necessary. During the growth process of bamboo, especially bamboo shoots, many phenomena related to water dynamics at the physiological level have yet to be fully understood. Since the underlying mechanism of water transport from the mature stem to the bamboo shoots as well as its relationship with carbohydrate transport remains unclear, further investigation is warranted. Future research should pay more attention to the molecular mechanisms of guttation, water transport, and aquaporin regulation.
2.4. Bamboo Sheath Affects Internode Growth
Studies have shown that culm sheath plays an important role in controlling water and assimilative transport Figure 3). In addition to the apical meristem
3. Conclusions
The sheath blade was the main organ of guttation in bamboo shoots, whose guttation droplets contain organic acids, sugars, hormones, and other compounds. The abundant conduit in the culm sheath was connected with that for the node of the bamboo shoot, which channels water and carries other substances to the culm sheath. The guttation process was jointly influenced by the local environment and physiological conditions of the bamboo plants. Removing their culm sheath damaged the internal homeostasis of water and material transport, thereby impairing the normal growth of bamboo shoots.