Allometry and morphophysiology of papaya seedlings in a substrate with polymer under irrigation with saline water

Abstract

The availability and quality of the irrigation water are among the limitations for the development of agriculture in the semiarid. Aiming at gathering information on these limitations, this work aimed to evaluate the association between a water-absorbing polymer and water salinity in irrigation frequencies, as well as container volumes on the allometric and morphophysiological indices of seedlings of the papaya (Carica papaya) cultivar ‘Sunrise Solo’. The treatments were obtained from the combination between the water-absorbing polymer (0.0; 0.2; 0.6; 1.0, and; 1.2 g dm-3), the electrical conductivity of the irrigation water (0.3; 1.1; 2.7; 4.3, and; 5.0 dS m-1), and irrigation frequencies (daily and alternate), plus two additional treatments (0.75 and 1.30 dm3) to study the effects of the container volume, distributed in a randomized block design. At 55 days after sowing, the following characteristics were evaluated: ratio between stem height and diameter; ratio between shoot and root dry matter; root density; leaf blade area; ratio between total leaf area and root dry mass; specific leaf area; leaf area ratio; leaf mass ratio; and Dickson quality index. The allometric and morphophysiological indices were damaged by the increase of water electrical conductivity and favored by the application of the polymer and a higher irrigation frequency. In the production of papaya seedlings, a daily irrigation frequency must be prioritized, using containers of 0.75 or 1.30 dm-3, water with electrical conductivity up to 2.6 and 1.9 dS m-1 when irrigated daily or in alternate days, respectively, and 0.6 g dm-3 of polymer.

Physiology in Talisia esculenta seedlings under irrigation with saline water on substrate with hydrogel

“…This effect causes delay and reduction of seedling emergence under saline conditions (Bezerra et al, 2014;Sá et al, 2015;F. S. Oliveira et al, 2016) as observed in T. esculenta (Figure 3), in addition to promoting lower growth of seedlings of this species (Melo et al, 2017) and of other species such as, for example, P. edulis (Bezerra et al, 2014(Bezerra et al, , 2019, A. squamosa (A. R. Silva et al, 2018a,b), A. heterophyllus (Oliveira et al, 2017), Pistacia vera L. (Rahneshan et al, 2018), Carica papaya L. (E. C. Nascimento et al, 2020), Solanum lycopersicum L. (Shin et al, 2020). The leaf index of chlorophyll a in T. esculenta seedlings was not affected by the linear interaction between electrical conductivity of water and polymer, and there was no adjustment for salinity (F ≤ 1.43; p > 0.10).…”

“…(Melo et al, 2017). The increase in soluble salts, in addition to reducing the water potential and consequently hindering water absorption, causes specific toxic effects of the ions (Taiz, Zeiger, Møller, & Murphy, 2017) and, in excess, can change the concentration of chlorophyll (Rahneshan, Nasibi, & Moghadam, 2018;Shin, Bhandari, Cho, & Lee, 2020) and quantum kinetics (Baker, 2008), limiting the energy flow for CO 2 assimilation; as well as gas exchange (H. H. C. Nascimento, Santos, Freira, Silva, & Nogueira, 2015) and biochemical reactions in chloroplasts (Cruz, Coelho, Coelho, & Santos, 2017) resulting in allometric and morphophysiological changes (E. C. Nascimento et al, 2020).…”

“…Water-retaining polymer, in addition to allowing an increase in the interval between irrigations, has the potential to reduce nutrient losses due to leaching (Navroski et al, 2015). However, not only the depth but also the frequency of irrigation can affect the performance of seedlings (A. R. Silva et al, 2018a,b;E. C. Nascimento et al, 2020) if poorly planned, and can economically burden the agricultural activity by using energy and/ or hand labor.…”

“…The adequacy of the volume of containers is also a relevant factor impacting the production of seedlings (A. R. Silva et al, 2018a,b;E. C. Nascimento et al, 2020) as the root restriction determined by the smaller volume of container can change the fluorescence and gas exchange (Ouma, 2007;Dias et al, 2018).…”