Fruit and seed ontogeny related to the seed behaviour of two tropical species of Caesalpinia (Leguminosae)

Abstract

Caesalpinia echinata and C. ferrea var. ferrea have different seed behaviours and seed and fruit types. Comparison of the seed ontogeny and anatomy partly explained the differences in seed behaviour between these two species of Brazilian legumes; some differences were also related to fruit development. The seed coat in C. ferrea consisted of two layers of osteosclereids, as well as macrosclereids and fibres, to form a typical legume seed coat, whereas C. echinata had only macrosclereids and fibres. In C. echinata, the developing seed coat had paracytic stomata, a feature rarely found in legume seeds. These seed coat features may account for the low longevity of C. echinata seeds. The embryogeny was similar in both species, with no differences in the relationship between embryo growth and seed growth. The seeds of both species behaved as typical endospermic seeds, despite their different morphological classification (exendospermic orthodox seeds were described for C. echinata and endospermic orthodox seeds for C. ferrea). Embryo growth in C. ferrea accelerated when the sclerenchyma of the pericarp was developing, whereas embryonic growth in C. echinata was associated with the conclusion of spine and secretory reservoir development in the pericarp. Other features observed included an endothelial layer that secreted mucilage in both species, a nucellar summit, which grew up into the micropyle, and a placental obturator that connected the ovarian tissue to the ovule in C. ferrea.

Development of megagametophyte, embryo, and seed in Senna corymbosa (Lam.) H.S. Irwin & Barneby (Leguminosae – Caesalpinioideae)

“…Corner (1951) mentioned this occurrence for diverse genera such as Caesalpinia , Peltophorum , Gleditsia , Cercidium , Parkinsonia , Bauhinia , and Erythrophloeum . A recent report (De Pádua Teixeira et al ., 2004) also revealed endospermic seeds in Caesalpinia ferrea Mart. Thus, the developed seeds of Senna corymbosa and other diverse representatives of Caesalpinioideae cannot be considered as completely exalbuminous, despite the seemingly disorganized remnants of this tissue.…”

“…A few representatives of Caesalpinioideae, such as Caesalpinia echinata Lam. (De Pádua Teixeira et al ., 2004), present paracytic stomata in their developing seed coat.…”

“…Although mostly conspicuous in the Papilionoideae, the hourglass layer is rudimentary or absent in diverse Caesalpinioideae such as Bauhinia and Caesalpinia, although it is well developed in many Cassia species (Corner, 1951), with some exceptions, such as Cassia auriculata (Suri & Deshpande, 1981). However, two layers of osteosclereids were observed in Caesalpinia echinata and Caesalpinia ferrea (De Pádua Teixeira et al ., 2004).…”

“…In most Leguminosae, the inner ovular integument is completely destroyed during seed development and does not take part in seed coat formation (Prakash, 1987). However, an endothelial layer or integumentary tapetum develops from this integument in Caesalpinia echinata and Caesalpinia ferrea (De Pádua Teixeira et al ., 2004), which was not observed in Senna corymbosa .…”

“…Most reports for the subfamily Caesalpinioideae concern Euro‐Asiatic species and diverse North American representatives. However, some Brazilian species of this subfamily have been investigated embryologically more recently (Oliveira, 1999), including the seed coat (Melo‐Pinna, Martins‐Neiva & Alencar Barboza, 1999) and the relationship between seed behaviour and anatomy (De Pádua Teixeira, Carmello‐Guerreiro & Rodriguez, 2004). A recent report by Delachiave & Zambello de Pinho (2003) about seed germination of the medicinal species, Senna occidentalis (L.) Link, also shows that knowledge of seed anatomy provides useful complementary data for the interpretation of physiological results about legume seed biology.…”