Somatic embryogenesis is a complex process regulated by numerous factors. The identification of proteins that are differentially expressed during plant development could result in the development of molecular markers of plant metabolism and provide information contributing to the monitoring and understanding of different biological responses. In addition, the identification of molecular markers could lead to the optimization of protocols allowing the use of biotechnology for papaya propagation and reproduction. This work aimed to investigate the effects of polyethylene glycol (PEG) on somatic embryo development and the protein expression profile during somatic embryo maturation in papaya (Carica papaya L.).

Coffea canephora cultivation areas in Brazil are frequently exposed to successive cycles of water deficit, triggering plant stress responses. In addition to water deficit, increased air temperature can act as a second stress factor. The recurrence of these stress factors may induce plant tolerance mechanisms, potentially mitigating future stress responses even of a different stress nature. We hypothesized that repeated cycles of water deficit can trigger tolerance mechanisms that make C. canephora leaves more resilient to supra-optimal temperatures. To test this hypothesis, young C. canephora plants were grown under non-limited water conditions for seven months (Ψ_mSoil > −20 kPa), after which they were subjected to two consecutive cycles of water deficit (Ψ_mSoil < −300 kPa), followed by rehydration. Two clones were used, ‘A1’ and ‘3V’, previously classified as drought sensitive and tolerant, respectively, considering the dynamics of physiological and architectural responses. After the second cycle, leaf discs were collected from completely expanded leaves formed during the two stress cycles and exposed to heat treatments (35 °C, 40 °C, 45 °C, 50 °C, and 55 °C) for 15 min in a water bath. Chlorophyll a fluorescence emission was then monitored, and the results were analyzed using OJIP transient kinetics and the JIP_Test. High temperatures induced negative changes in both OJIP kinetics and JIP_Test-derived parameters. A significant increase in F₀ and a reduction in F_M were observed mainly at 50 °C and 55 °C, due to changes in the stages of the OJIP curve. These changes impacted the “energy connectivity” and consequently the electron transport along the electron transfer chain (ETC), increasing energy dissipation, as confirmed by the JIP_Test variables. Despite the high temperature impacts, previous water deficit induced heat tolerance in clone ‘A1’, while it increased sensitivity in clone ‘3V’. This study suggests that selecting drought-resistant varieties should consider their subsequent response to short high-temperature stress to avoid cross-sensitivity caused by selecting for a single environmental factor.

This book chapter initially shows the actions of anthropogenic activities on climate change and how this future scenario can cause water stress in fruit plants, notably through the reduction in water availability caused by drought. Thus, only through advanced knowledge of fruit tree physiology is it possible to apply water in a controlled manner, lowering costs and increasing yield, thereby reducing the water footprint (L per kg of fruit) and improving agronomic and economic water use efficiency, as well as fruit quality. After the introductory part, the basic concepts of water availability in soil, plants and air are shown, as well as methodologies for measuring water status in the soil–plant-atmosphere system. Furthermore, the chapter addresses the effects of water limitation associated with reduced availability of water in the soil and air on the photosynthetic process, the phytohormonal imbalance associated with abscisic acid (ABA), and hydraulic conductivity on the productivity and quality of fruit plants.

A melatonina, uma molécula derivada do triptofano, está presente em diversos organismos, incluindo as plantas. Nas plantas, ela desempenha um papel essencial, influenciando processos cruciais como crescimento, desenvolvimento e resposta a estresses bióticos e abióticos. A melatonina interage com outros fitormônios, contribuindo para sua regulação e atua como um potente antioxidante, eliminando espécies reativas de oxigênio e nitrogênio. Além disso, estudos recentes apontam que o uso da melatonina exógena favorece o aumento da vida útil pós-colheita de frutas e verduras, garantindo produtos de qualidade e ambientalmente amigáveis. Esta revisão tem como objetivo reunir as principais características da melatonina em plantas e destacar sua importância, gerando um material de consulta em língua portuguesa para estudantes. Além disso, busca incentivar mais pesquisas e a inclusão do tema na grade curricular de disciplinas como Fisiologia Vegetal nas universidades.