Advancing Endodormancy Release in Temperate Fruit Trees Using Agrochemical Treatments

Endodormancy in temperate fruit trees like Prunus is a protector state that allows the trees to survive in the adverse conditions of autumn and winter. During this process, plants accumulate chill hours. Flower buds require a certain number of chill hours to release from endodormancy, known as chilling requirements. This step is crucial for proper flowering and fruit set, since incomplete fulfillment of the chilling requirements produces asynchronous flowering, resulting in low quality flowers, and fruits. In recent decades, global warming has endangered this chill accumulation. Because of this fact, many agrochemicals have been used to promote endodormancy release. One of the first and most efficient agrochemicals used for this purpose was hydrogen cyanamide. The application of this agrochemical has been found to advance endodormancy release and synchronize flowering time, compressing the flowering period and increasing production in many species, including apple, grapevine, kiwi, and peach. However, some studies have pointed to the toxicity of this agrochemical. Therefore, other non-toxic agrochemicals have been used in recent years. Among them, Erger® + Activ Erger® and Syncron® + NitroActive® have been the most popular alternatives. These two treatments have been shown to efficiently advance endodormancy release in most of the species in which they have been applied. In addition, other less popular agrochemicals have also been applied, but their efficiency is still unclear. In recent years, several studies have focused on the biochemical and genetic variation produced by these treatments, and significant variations have been observed in reactive oxygen species, abscisic acid (ABA), and gibberellin (GA) levels and in the genes responsible for their biosynthesis. Given the importance of this topic, future studies should focus on the discovery and development of new environmentally friendly agrochemicals for improving the modulation of endodormancy release and look more deeply into the effects of these treatments in plants.

Heterologous expression of MiHAK14 enhances plant tolerance to K+ deficiency and salinity stresses in Arabidopsis

As one of the most abundant ions in cells, potassium (K+) is closely related to plant growth and development and contributes to plant tolerance to various abiotic stresses. However molecular mechanisms towards K+ uptake and transport are unclear in tropic fruit trees. In this study, 18 KT/HAK/KUP family genes (MiHAKs) were isolated and characterized in mango. Results showed that MiHAKs were unevenly expressed in distinct tissues and were differentially responded to K+ depletion, PEG, and NaCl stresses in roots, in which K+ depletion and PEG treatment significantly enhanced while NaCl treatment mainly reduced responsive MiHAK genes. In particular, MiHAK14 was the most abundant KT/HAK/KUP family gene in mango, especially in roots. Functional complementation in TK2420 mutant revealed that MiHAK14 could uptake external K+. Moreover, overexpression of MiHAK14 in Arabidopsis enhanced plant tolerance to K+ depletion and NaCl stresses with strengthened K+ nutritional status and ROS scavenging ability. This study provides molecular basis for further functional studies of KT/HAK/KUP transporters in tropic fruit trees, and favorably demonstrates the essentiality of K+ homeostasis in plant tolerance to abiotic stresses, including K+ deficiency and NaCl stress.

Identification of plant genetic resources affected by shrimp farming in the southwestern coastal region of Bangladesh

The main purpose of the study was to identify the plant genetic resources (PGRs) affected by shrimp farming and to determine their magnitude of vulnerability. Data were collected from randomly selected 100 respondents, through personal interview, using an interview schedule, at Dumuria upazila of Khulna district, during 16 November 2009 to 15 February 2010. The fruit PGRs were more affected by shrimp farming than that of timber yielding and other types of PGRs. Among the 18-fruit PGRs available, all were endangered, except indigenous velvet apple, Diospyros peregrine (Gaertn.) Gürke, which was in threatened condition. Among the fruit species, banana, Musa acuminate; guava, Psidium guajava L.; jackfruit, Artocarpus heterophyllus Lam.; sapota, Manilkara zapota L. and betel nut, Areca catechu L. were in highly endangered. Among the 17-timber yielding and other plant species, only 7-PGRs were affected by shrimp farming while majority (10-PGRs) had been available in different extents. Among the vulnerable PGRs, bamboo, Bambusa bambos (L.) Voss; flame of the forest, Delonix regia (Boj. ex Hook.) Raf.; teak, Tectona grandis L.f. and banyan, Ficus benghalensis L. were endangered, while Indian ash tree, Lannea coromandelica (Houtt.) Merr.; ipil-ipil, Leucaena leucocephala (Lam.) de Wit and cool mat, Schumannianthus dichotomus (Roxb.) Gagnep. were in threatened condition. In general, the total fruit trees decreased in numbers (-74.17%) after inception of shrimp farming. On the other hand, the total numbers of timber yielding plants increased by 15.45%. From the overall consideration (irrespective of types), the number of plant population decreased (-58.10%) after inception of shrimp farming. It means that the plant species were affected by shrimp farming and became endangered. Int. J. Agril. Res. Innov. Tech. 11(2): 18-26, Dec 2021

Uptake and assimilation of nutrient resources.

Fruit trees require six macronutrients (N, P, K, calcium, Mg and sulfur) and eight micronutrients (Zn, Fe, B, Mn, Cu, chlorine, nickel and molybdenum) that are taken up through the roots. Many of these occur naturally in the soil as cations bound to negatively charged soil particles, while others are dissolved in the liquid surrounding the soil particles in the form of anions. This chapter discusses the uptake and assimilation of nutrient resources in fruit trees. Tabulated data are given on mean annual N, P and K storage (kg/ha) in perennial organs of mature almond trees that received N fertilizer at 309 kg/ha.

Energy capture and carbon assimilation.

This chapter focuses on energy capture and carbon assimilation of fruit trees. It discusses the factors affecting photosynthesis and respiration, including temperature, carbon dioxide concentration, nutrient supply, water availability, oxygen, and carbohydrates.

The structure of trees.

Trees are, by definition, the tallest land plants. To grow tall over multiple years they must solve several problems: structural strength; carbohydrate and nutrient storage capacity to survive and regrow after periods of stress; and conductive capacity for water, carbohydrates and nutrients must be increased/renewed over time to keep pace with increases in canopy size. Additionally, apical meristems must be capable of surviving through periods of stress (especially over winter or during drought). Structural strength, storage capacity and water, carbohydrate and nutrient conductive capacity are provided by cells derived from a sheath of meristematic cells (vascular cambium) that surround the body of trees (shoots, stems, branches, trunk, perennial roots). This chapter describes the structure of fruit trees.

The carbohydrate economy of fruit trees.

Since lack of water is a commonly occurring condition in nature, plants have developed many physiological responses to help them survive periods of water stress. Most of these responses cause changes in the carbohydrate economy of the tree through reduced photosynthesis, tree growth or cropping, but some of these effects can be managed to have minimal impact on overall tree productivity. Whether these responses influence economic production depends on: (i) the processes occurring at the time of a stress; (ii) how important these processes are to tree yield; and (iii) whether these processes rely heavily on the current level of photosynthesis or can use stored carbohydrates, like starch, to compensate for the lack of current photosynthesis in the leaves. This chapter discusses the carbohydrate economy of fruit trees. An outline is provided for how assimilates are distributed and used within a fruit or nut tree.

Application of shoot growth rules for understanding responses to pruning.

Knowledge of fruit tree shoot types is helpful to explain why pruning is often not successful in reducing tree size. In many horticultural circumstances, epicormic shoot growth can be considered as being almost exclusively stimulated by severe pruning of large branches (older than one year old) or strong water shoots in which sylleptic shoots have previously grown and "used up" the locations in close proximity to the pruning cut where proleptic buds would have been present in a less vigorous shoot. The strong growth response to heavy pruning is natural and is the primary reason why pruning cannot be relied upon exclusively to control tree size when trees are grown in highly fertile soils without size-controlling rootstocks. This chapter deals with understanding responses to pruning of fruit trees by application of shoot growth rules.